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3s2: Plant biotechnology > Week 4 > Flashcards

Week 4 Flashcards

1
Q

What is genetic transformation?

A

Genetic transformation is defined as the directed desirable transfer of gene from one organism to another along with the subsequent stable integration and expression of a foreign gene in the genome

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2
Q

What is transgene?

A

The gene that is transferred

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3
Q

What is transgenics?

A

The organisms that are formed after a successful gene transfer

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4
Q

What is plant transformation?

A

It is defined as the method of insertion of DNA from another organism, usually a plant gene, into the genome of the plant of interest

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5
Q

What is key for sucessful transformation/gene editing?

A

A regenerable target tissue.
An efficient method of introducing the new gene or gene editing components
A suitable DNA construct to introduce the transgene into the host plant
A good selection system so that transgenic material can be distinguished from non-transgenic

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6
Q

What are visual markers for gene transfer?

A

GFP - protein that exhibits green fluorescence when exposed to light in the blue to ultraviolet range
Ruby - transgenic cells are distinctly red and visible to the naked eye
GUS - GUS gene produces blue coloration in plants upon integration into the plant genome

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7
Q

What are antibiotic resistance selectable markers?

A

NptII – kanamycin resistance
Hpt – hygromycin resistance
(Need appropriate promoters for selectable marker and gene of interest)

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8
Q

What are Herbicide resistance genes selectable markers?

A

Bar – resistance to the herbicides basta and bialaphos - active ingredient phosphinothricin (PPT)
(Need appropriate promoters for selectable marker and gene of interest)

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9
Q

What are the methods for introducing new genes or gene editing components?

A

Agrobacterium-Mediated
Biolistic
Protoplasts

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10
Q

What is an overview of Agrobacterium-mediated gene editing?

A

This method uses a natural bacterium’s ability to transfer DNA into plant cells, resulting in stable and inheritable genetic changes

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11
Q

What is an overview of biolistic?

A

Physically breaching the plant cell wall and membrane with gold or tungsten microprojectiles coated with biomolecules accelerated to very high velocities

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12
Q

What is an overview of protoplasts?

A

Protoplasts are treated with DNA in the presence of PEG.
Protoplasts are isolated cells produced by removing the surrounding cell wall either by mechanical means or by the use of cell wall degrading enzymes

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13
Q

What is needed on a wildtype Ti-Plasmid?

A

Virulence region
T-DNA
Opine Catabolism
Origin of replication

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14
Q

What is an overview of virulence region?

A

The virulence region codes for virulence genes that are responsible for the transfer of T-DNA to the plant cells and also recruiting various effector proteins for infecting the plant cells

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15
Q

What is an overview of T-DNA?

A

The T-DNA region is the crucial region that gets transferred to the plant cell for infection. It is approximately 15-20 kbp in length and is transferred to the plant cell via means of genetic recombination

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16
Q

What is an overview of opine catabolism?

A

The opine catabolism region is the region from where the bacteria sources its nutrients for the whole process.
Opines are derivatives of amino acid or sugar phosphates that can be catabolized to use in the form of nutrients.
The types of opines found in Ti-plasmid are nopaline and octopine types

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17
Q

What is an overview of origin of replication?

A

The origin of replication is the region where replication of the plasmid is initiated

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18
Q

What is an overview of binary vector system for transformation?

A

Vir region on disarmed Ti plasmid:
virF, virA, virG, virC, virD and virE

Binary vector contains:
LB - GOI - T-DNA - Selection marker - RB

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19
Q

What is an overview of antibiotic selection markers?

A

NptII – kanamycin resistance, Hpt – hygromycin resistance

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20
Q

What is an overview of herbicide selection markers?

A

Bar – resistance to the herbicides basta and bialaphos - active ingredient phosphinothricin (PPT)

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21
Q

What is biolistic method for gene transfer?

A

Millions of DNA-coated metal particles are shot at target cells or tissues using a biolistic device or gene gun.

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22
Q

What are the advatages of disadvantages of agrobacterium method?

A

Pros - High efficiency and stability
Cons - Limited to specific crop species

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23
Q

What are the disadvantages of biolostic method?

A

Pros - Wide range of plant species
Cons - Higher T-DNA integration and Low efficiency and random integration

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24
Q

What is protoplast transfection?

A

Protoplast-mediated transformation involves direct uptake of DNA by naked plant cells (plants without a cell wall, or protoplasts). This process provides an expression system for researchers to identify novel candidate genes

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25
Q

Why might protoplast transfection be used?

A

The protoplast technology is an excellent method for creating a rapid and effective tool for transient expression and transformation assays, particularly in plants that lack an Agrobacterium-mediated plant transformation system

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26
Q

What are examples of other DNA delivery systems?

A

Gene-editing by expression of developmental regulators and de novo meristem induction in plants.
RNA viruses and mobile guide RNAs for heritable plant gene-editing.
Nanoparticles for delivering biomolecules to facilitate plant genome engineering

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27
Q

What are examples of tissues targeted for transformation?

A

Immature embryos (cereals)
Mature embryos
Suspension cultures
Protoplasts
Hypocotyl explants
Cotyledonary petioles (Brassicas)

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28
Q

What is an overview of the regeneration method?

A

Explants
Regeneration
Transgenic plants on selection medium

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29
Q

What is an overview of the method for tissue culture free genome editing by de novo meristem induction in tomatoes?

A

Remove existing meristem
Introduce reagents
Meristem formation
Growth with fixed modifications
Segregation of modification in offspring

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30
Q

What is an downside of the method for tissue culture free genome editing by de novo meristem induction in tomatoes?

A

Only really possible in tomaotes as other plants may struggle
Also ineffcient

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31
Q

What is an overview of using nanoparticles for delivering biomolecules to enginner plant genomes?

A

Single walled carbon nanotubes (CNTs) (~1 - 1000 nm) and carbon dots (~3 nm)
Delivery using syringe through stomata
DNA-CNTs traverse the cell wall and membranes and modifies DNA

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32
Q

What are the two steps for plant transformation?

A

T-DNA integration
Regeneration (Somatic embryogenesis/ organogenesis)

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33
Q

What are plant growth regulators that impact regeneration of plant cells?

A

Type, concentration and ratio of:
Cytokines
Gibberellin
Auxin
Other

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34
Q

What are species/genotypes that impact regeneration of plant cells?

A

Type
Age
Size
Orientation

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35
Q

What are basal culture medium that impact regeneration of plant cells?

A

Mineral nutrients
Vitamins
Carbon sources
pH

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36
Q

What are culture conditions that impact regeneration of plant cells?

A

Temperature
Light

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37
Q

What is an overview of genetic transformation protocol in wheat?

A

Identify the spike with right stage of immature embryos (IEs) and isolate
Centrifuge and co-cultivate IEs with Agrobacterium for 3 days
Excise embryonic axis 5 days later and culture in resting medium and under hygromycin selection +5 weeks
Culture in regeneration and rooting media 2 weeks + further 2 weeks
Transfer to soil
Analysis

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38
Q

What is an overview of wheat transformation system at JIC?

A

Target tissue: Immature embryos
Delivery method: Agrobacterium strain AGL1
Selection system: Hygromycin resistance alternative selection G148
Genotype: Fielder (US spring wheat)
Constructs: initially pBRACT series, now superseded by pGGG

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39
Q

What is an overview of the transformation efficiency at JIC?

A

Transformation efficiencies of up to 25%
Spring wheat cv ‘Fielder’ (Calculated 1 plant from 1 embryo)

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40
Q

What is an overview of gene-editing by expression of developmental regulators?

A

Genes: PGA37/MYB118, Wus2, Bbm, Shoot Meristemless (STM) and Wox5
Meristematic and embryogenic genes

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41
Q

What are the downsides of gene-editing by expression of developmental regulators?

A

Continued expression of the genes can cause developmental defects.
Plant regeneration using these technologies requires controlled expression or removal of the expression cassettes.
So far, limited activity in dicots

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42
Q

What is an overview of GRF-GIF chimeric protein improvments?

A

GRF-GIF –> Growth regulation factor
Significantly increased the transformation efficiency
Reduced the time of transformation process (from 90 to 50 days)
Reduced constrains that limit transformation efficiency (plant condition, embryo size …).
Expands the range of transformable genotype.
The GRF4–GIF1 technology results in fertile and normal transgenic plants

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43
Q

What is an overview of GRF-GIF fusion in conjunction with our transformation system?

A

Expanded the transformable genotypes
Allowed us to transform elite commercial varieties
Varieties such as Skyfall, Reedling, Paragon and Cadenza

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44
Q

What’s an overview of the expression of Baby boom (Bbm)
and Wuschel2 (Wus2) generation?

A

Embryo from mature seed
Innoculated with agrobacterium
Generate callus
CRE excises BBM/WUS construct
Select transformed callus with BBM/WUS contruct excised

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45
Q

What’s an overview of the expression of Baby boom (Bbm)
and Wuschel2 (Wus2) results?

A

Single somatic embryos on the surface of Fast-Flowering - induced by Wus2 and Bbmexpression

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46
Q

What is an application of crop transformation for increased yield?

A

Crop transformation technologies can lead to higher crop yields, helping to meet the growing demands of a growing population

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47
Q

What is an application of crop transformation for enhanced nutritional value?

A

Genes can be inserted to increase the amount of essential nutrients, such as vitamins and minerals, in crops

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48
Q

What is an application of crop transformation for disease resistance?

A

Crops can be engineered to express proteins that combat pests, pathogens, and viruses, reducing reliance on pesticides

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49
Q

What is a potential application of gene transformation

A

Increased shelf life banana
Wheat with decreased land - single mutant +6% weight, double +11% weight and triple +21% weight
Rust resistance BCAT1

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50
Q

What is transgenesis and cisgenesis?

A

Transgenesis refers to inserted DNA originating from a sexually incompatible species
Cisgenesis refers to inserted DNA originating from the same or a related species that is sexually compatible

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51
Q

What is are CIS genes?

A

Cisgenes generally include the introns and flanking native
promoter and terminator in the same orientation

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52
Q

What is an overview of nitrogen abundance?

A

Most abundant element in the earth’s atmosphere
4th most abundant element in a plant (after C, H and O)
Usually the limiting nutrient for plant growth
Nitrogen is one of the three major macronutrients found in most fertilizers NPK

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53
Q

What is an overview of nitrogen use in plants?

A

N is in amino acids (proteins), nucleic acids (DNA, RNA), chlorophyll, and countless small molecules

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54
Q

What are the two mechanisms for nitrogen fixation?

A

Biological fixation through microorganisms (120 Tg N/ yr
Industrial fixation through haber bosch process

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55
Q

What is an overview of the green revolution?

A

1909 - Haber-Bosch synthesis of ammonia from N2
1930s - late 1960s - Green Revolution - Breeding programes
Population rose from 2 billion in 1900 to 6,148,898,975

56
Q

What is an overview of nitrogen in prokaryotes?

A

Many prokaryotes oxidize NH4+, so soil NH4+ levels are often low
Ammonium to nitrate through nitrification

57
Q

What is an overview of nitrogen processes in plants?

A

Plants use energy to reduce NO3- for assimilation into organic compounds
NH4+ is added to amino acids to create R-NH3

58
Q

What is an overview of plant preference of nitrogen source?

A

Plant preferences for NO3- vs NH4 + varies by species and depend on the environment - temperature, water, soil pH. But most plants grow best with a mixed supply

59
Q

What are the problems with current nitrogen production and usage?

A

Nitrogen fixation is energy demanding
Nitrous oxide (N2O) derived from fertilizer is a major greenhouse gas - areas pf nebraska and california with >10 mg/L of nitrate
Unhealthy nitrate from agricultural uses pollutes groundwater - creates cyanobacteria/algal blooms which suffoctated aquatic life

60
Q

What is an overview of the N problem in the UK?

A

Between 60-40% applied N not taken by crop
UK farmers apply an average of 190 kg of N based fertiliser per hectare of crop each year
70% of nitrate in inland waters is estimated to come from agriculture
N eutrophication costs year-1 in England and Wales estimated £150 million (Defra)

61
Q

What is an overview of nitrate toxicity?

A

Two main health issues:
(i) infant methaemoglobinaemia (blue baby syndrome)
(ii) cancers of the digestive tract.
But there is evidence of a possible benefit of nitrate in cardiovascular health

62
Q

What is an overview Fertiliser Use Efficiency?

A

Fertiliser Use Efficiency (FUE)
% of applied fertiliser recovered by crop

63
Q

What is an overview Nitrogen Uptake Efficiency?

A

Nitrogen Uptake Efficiency (NUpE)
N-uptake/N-available (Nup/Nav)

64
Q

What is an overview of Nitrogen Utilisation Efficiency?

A

Nitrogen Utilisation Efficiency (NUtE)
Grain yield/N-uptake (Y/Nup)

65
Q

What is an overview of Nitrogen Use Efficiency?

A

Nitrogen Use Efficiency (NUE)
Uptake efficiency x Utilisation efficiency
NUE = Nup/Nav x Y/Nup = Y/Nav

66
Q

What is a comparison of 50 year NUE in China and the UK?

A

1960 vs 2010
UK = 28% –> 50%
China = 86% to 27%

67
Q

What is NHI?

A

NHI – N Harvest Index (the fraction of N in the grain relative to the total N taken up, usually at harvest)

68
Q

How to improve nitrogen-use efficiency and decrease N pollution?

A

Matching crop demand and soil supply
Supply – N in the soil
Demand – the needs of the crop
Supply (soil) = Demand (crop)
When they done overlap N loss

69
Q

What is an overview of experiment matching N supply and demand in the field

A

Grain yield peaks at ~150 Kg/ha 9t/ha
However as N fertiliser increases yield doesnt 300 Kg/ha 8.7t/ha
Leaching increases overtime 150kg/ha 60kg/ha compared to 300 Kg/ha at 150kg/ha

70
Q

What is an overview of crop demand changes with development?

A

Early Stem extension requires large about of nitrogen due to large amount of growth
Later in life it requires a smaller amount of nitrogen such as ripening (grain development)
Late life crop can remobalise nitrogen from elsewhere in plants

71
Q

What is an overview of the strategies to improve NUE and decrease
N pollution?

A

Soil available N
Rhizosphere – root/soil interface
Root architecture
Root transporters for uptake

72
Q

How can you measure the soil nitrogen supply?

A

Suction cup lysimeters – soil water sample for lab analysis
Soil core sample – lab analysis
Plants as indicators
Soil sensors

73
Q

What is an overview of soil water nitrate observation in different wheat cultivars?

A

Soil water nitrate concentrations measured under wheat seedlings at 3 depths for 14 hours.
Comparing 2 wheat cultivars – Maris Widgeon (low NUpE) and Robigus (high NUpE)

74
Q

What were the results of observing two different wheat strains with soil water nitrate observation?

A

Similar soil [NO3] measured for the two cultivars at mid and base levels
Decrease of the [NO3] under the top layer of the ROBIGUS
ROBIGUS as bred for better at abosrbing nitrate at higher levels due to more lateral roots at top layer

75
Q

What is LoRA?

A

LoRa Telemetry: Geo-location and live data
Sensor is geo-located, data transmitted via gateway to cloud, and live data available on web based system

76
Q

What is an overview of slow-release fertilizers can match
release to crop requirements

A

Traditional fertilizers don’t match nitrogen availability to plant needs.
Slow release fertilizers can more closely match plant needs

77
Q

What is an example of a slow releasing fertiliser?

A

Coated urea dissolves and releases slowly, but it can be expensive

78
Q

What is an overview bi-cropping with legumes?

A

Bi-cropping with a legume (N2 fixing plant) eg Maize and soybean
Co-cropping or growing in rotation with legumes enriches soil N content
Cover crops in the autumn in the UK (green manures)

79
Q

What is an overview of Rhizosphere processing of N (root exudates
and microbes)?

A

Understanding process as NO3- is most mobile form, negative charge, so understanding how it works and root exudates to alter nitrification keeping more fertiliser as NH4+ less leeching occurs

80
Q

Can soil bacteria be manipulated to decrease
N2O and NO3- pollution?

A

Inhibitors of bacterial nitrification cause NH4+ to be retained in the soil, leading to less leaching and less N2O production
Denitrifying bacteria cultivated in a bioreactor downstream of a fertilized field protect waterways by converting NO3- in runoff to N2

81
Q

What is an overview of root response to nitrogen avaliability?

A

When nitrogen is abundant, plants allocate less biomass to their roots
When nitrogen distribution is patchy, roots proliferate in the nutrient rich patches

82
Q

What is an overview of nitrogen transporters?

A

Plants have specific transporters for NO3-, NH4+, amino acids and urea uptake
HATS = high affinity transporters
LATS = low affinity transporters

83
Q

What happens when you upregulate transporters?

A

Nitrogen feedback system regulates –> increased uptake in nitrogen transporter can lead to increased efflux maintaining equilibrium

84
Q

What is an overview of NUtE – N utilisation as a target?

A

Assimilation of N
Remobilization of stored N
Measuring crop N status and demand

85
Q

What is Crop N status diagnostics?

A

Crop N status diagnostics: precision agriculture
Total-N, P, K, S
Unreduced/stored (NO3, PO4, SO4)
Metabolites (chlorophyll, glutathione, malate)
Gene expression (PCR test)

86
Q

What is an overview of SPAD meter?

A

Testing crops - chlorophyll
* Chlorophyll & nitrogen
* Growth & yield
* Variation: interactions
But if measure change in field means too late to get maximum yield

87
Q

What are some main processes in nitrogen metabolism in plants?

A

Assimilation - Carbon pools and TCA cycle
Remobalisation - Amino acid recycling, photorespiration
Incorporation into amino acids and other nitrogen-containing compounds from glutamate and glutamine
Glutamine synthetase (GS) is an important ezyme for nitrogen metabolism

88
Q

What is an overview of the remobalisation of nitrogen during senescence?

A

Each N atom may cycle through GS many times as amino acids are recycled during growth and senescence and released due to photorespiration

89
Q

What is an overview of glutamine synthase?

A

GS1 (GLN1 genes) Cytosolic protein
GS2 (GLN2 genes) Nuclear gene, plastid localized protein
GS activity is regulated transcriptionally and post-transcriptionally by cell type, light, [NH4+], circadian cycles, plant carbon status etc

90
Q

Why is glutamine synthase targeted for breeding increases for nitrogen use efficiency?

A

GS activity is correlated with nitrogen use efficiency

91
Q

What are examples of idealised traits for high yield high quality crops?

A

High remobalisation through GS
High levels of uptake through HATs and LATs
High assimilation through nitrite and nitrate reductases

92
Q

What is an overview of molecular targets for N signalling?

A

Molecular players in N signaling and regulation.
Targets for improving NUE (e.g. transcription factors, microRNAs)

93
Q

What is an overview of phosphorus?

A

The 11th most abundant element in the earth’s crust
The 5th most abundant element in a plant
The 2nd most commonly limiting nutrient for plant growth

94
Q

Why is phosphorus important?

A

P has roles in cell structure, energy (ATP) and information storage and energy and information transfer

95
Q

What is an overview of phosphorus form when assimilated?

A

Phosphorus (P) is assimilated and used as phosphate (Pi) which depending on the pH is H2PO4- ,HPO42- or PO43-
Acid pH H3PO4 at Alkaline pH PO43-

96
Q

What is an overview of the phosphorus cycle?

A

Plants are part of the global phosphorus cycle
Essentially no atmospheric pool of P (very different from N)

96
Q

How do humans impact the phosphorus cycle?

A

Mining and commercial processing accelerates P entry to biosphere
Urbanization removes P from terrestrial cycle and accelerates entry to waterways, causing toxic algal blooms (eutrophification)

97
Q

Is the current rate of phosphorus use sustainable?

A

Phosphate usage has increased dramatically in the past 70 years
Some have argued that we are approaching a period of “peak phosphorus” as deposits become depleted, peaking around 1990s
90% of the world’s phosphate rock reserves are found in 5 countries (Morocco 38%, China 27%)
With the current rate of phosphate rock exploration and production, the reserves are likely to be depleted in the next 260 years if no new reserves are added

98
Q

Is it feasible to reuse, recapture and recycle phosphate?

A

P recovered from human urine alone could replace >20% of P demands (Urine-reclaiming toilet)
Human urine is rich in P, and it can be separated from other waste at the point of origin
Urine can be applied directly to plants as liquid fertilizer

99
Q

How can P and N can be precipitated out of wastewate?

A

N & P-rich Wastewater in
Cleaner wastewater out
Struvite (NH₄MgPO₄·6H₂O) crystals harvested for use as fertilizer

100
Q

What is an overview of using urine as a fertiliser?

A

In Sweden this Gotland experiment compared barley fertilized with urine (right) to plants grown without fertilizer (middle) and ones with mineral fertilizer (left)
Urine works as a fertiliser

101
Q

What is an overview of soil phosphate distrubution?

A

Almost all P is found in the top 50 cm of soil

Used to show how much is avaliable?
Olsen P (neutral/alkaline soils) – extracted with sodium bicarbonate
Bray P (acidic soils) – ammonium fluoride extract

102
Q

What is an overview of phosphorus storage molecules?

A

Soil P:
Inorganic: Absorbed, precipitated or mineral
Organic: Absorbed or humic layers

Avaliable P: Soil solution dissovled HPO42- and H2PO41-

Soil microorganisms: Convert Soil P to Avaliable P by solubilisation and mineralisation the opposite can also be done via immobalisation

103
Q

What is an overview of phosphate leeching?

A

Like nitrate, phosphate can leach through the soil
When reaching change point, much higher levels of phosphate in drainage water

104
Q

What are strategies to impede P from entering waterways?

A

Timing of fertilizer application and management of water flow from can decrease the amount of P that enters waterways
Chemical and biological processes including algal production can effectively remove P from wastewaters (irrigation or animal feed recycling)

105
Q

What is an overview of soil phosphorus?

A

Phosphorus in soil is in the form of immobile, insoluble complexes
Cation-phosphate complexes Al-P are relatively insoluble and immobile in soil; these include oxides and hydroxides of Al and Fe
Also organic phosphate - plants do not take up organic phosphate
Roots growing in 31P-labeled soil. Only P immediately next to roots is taken up

106
Q

How do plants and microbes increase phosphate avaliability?

A

Exudates from free-living and symbiotic microbes also contribute to P solubilization
Such as:
Low Molecular Weight Organic Acids (LMWOA) - change pH and bind to metal in complex eg malate -> Al-Malate
Phytase-producing bacteria (Phytate = C6H18O24P6)
Phosphatases (enzymes) convert organic phosphates to avaliable form

107
Q

What is an overview with Arbuscular mycorrhizal fungi?

A

Arbuscular mycorrhizal fungi facilitate Puptake in most plants
~80% of plants associate with mycorrhizal fungi; these associations can facilitate P uptake

108
Q

What root systems can optimise phosphate foraging?

A

Reduced gravitropism
Increased formation and elongation of lateral roots and root hairs
Aerenchyma (air spaces that allow metabolically inexpensive growth)

109
Q

What is an overview of cluster roots?

A

Many species of the family Proteaceae found throughout the Southern Hemisphere make short-lived “proteoid” or “cluster” roots to facilitate P uptake
Cluster roots increase surface area and also root exudation such as phosphateses and proton pump to modify pH

110
Q

What is a model for cluster roots?

A

White lupin (Lupinus albus) is a cluster-root producing legume that provides a good genetic model

111
Q

What is an overview of PHT1?

A

PHT1 phosphate transporters mediate uptake and transport
Most are expressed in roots and other tissues 9 PHT1 genes in Arabidopsis, 13 in rice, 12 in poplar. Some are mycorrhiza inducible

112
Q

What is an overview of PHT transporters mechanism?

A

PHT transporters are H+ / PO43- co-transporters that have 12 membrane spanning domains

113
Q

What is an overview of P-starvation inducible (PSI) responses in Proteaceae?

A

Proteaceae show metabolic adaptions to Pimpoverished soils such as very efficient use
Ribosomes (rRNA) are the major form of organic P. Proteaceae maintain a very low copy number of ribosomes, yet are photosynthetically efficient
Proteaceae also show delayed greening; ribosomes first promote growth, then chloroplast maturation

114
Q

What is an overview of P-starvation inducible (PSI) response in shoots?

A

Increase in Pi recycling and remobalisation
Reduced rate of photosynthesis
Increased sugar concentration
Increased anthyocyanin accumulation
Reduced shoot growth

115
Q

What is an overview of P-starvation inducible (PSI) response in roots?

A

Increased Pi uptake, transport and translocation
Increased secretion of organic acids and acid phosphatases
Changes in metabolic pathways
Establish plant-mycorrhizal fungi symbiosis

116
Q

What is an overview of regulatory controls to prevent Pi form over accumulation?

A

PHO1 is a transporter that moves Pi into xylem for transport to the shoot PHT transporters take P
PHO2 is an E2 ligasethat targetstransporters for proteolysis

117
Q

What is an overview of PHO1 and PHO2?

A

In pho1 mutants, too much Pi accumulates in the root and too little in the shoot
In pho2 mutants, too much Pi accumulates in the shoot and too little in the root; transport is out-of-control

118
Q

What regulates P uptake and transport?

A

P uptake & transport are regulated by local and systemic signals:
Strigolactones - Establishment of plant – mycorrhizal fungi symbiosis
PHR1 (transcription factor) - PHT1 transporters, Phosphatases, organic acid synthases, IPS1 inhibits miR399 which inhibits PHO2 and PHO1

119
Q

Why is phosphate toxic? How is this overcome?

A

Can bind to important metal like iron
Phosphate can be stored as ‘phytate’.
In seeds phytate can make metals like iron and zinc less ‘available’ for uptake in the gut.

120
Q

Can SPAD meters be used as an indicator for crop demand?

A

Yes
Same advantages (Easy to measure, Sensitive to supply, Responds quickly) and problems (once problem detected too late)

121
Q

What is the critical threshold for Leaf phosphate (Pi) storage?

A

6 nM in wheat leaves

122
Q

What methods of Crop breeding traits for improving plant P nutrition?

A

Rhizosphere (exudates, acidification, enzymes)
Uptake systems (transporters, regulation)
Root architecture (root hairs, laterals, surface, depth gravitropism, penetration)
Assimilation (capture, stores, translocation, symbioses)
Symbioses (fungi - mycorrhization for P; phosphate solubilising bacteria)

123
Q

What is an overview of transgenic lines can show enhanced P uptake?

A

Modifying regulators of P signaling network
Releasing Pi from insoluble pools (through organic acid extrusion, proton pumping, and phosphatases)
Optimizing root architecture
Enhancing high affinity uptake (PHT1 transporter)

Success has been mixed, internal regulation increased expulsion

124
Q

What is an overview of selection for root architecture?

A

Selection for root architecture traits can lead to increased P uptake
Select for cultivars on low P soil with top heavy root system

125
Q

What is an overview of rice adaption to low-P?

A

The Pup1 (Phosphate Uptake 1) major QTL was identified in ausvariety rice adapted to poor soils
Eventually this was revealed to encode a protein kinase PSTOL1 not present in other rice genomes
Overexpression of PSTOL1 leads to enhanced root growth

126
Q

What can be atrributed to symbiosis for phosphate uptake?

A

The effect of strigolactones (SLs) on the host plant, the arbuscular mycorrhizal (AM) fungus and its endobacteria during the establishment of AM

127
Q

What is an overview of improving distrubution of Pi between tissue?

A

A1- enhancing Pi transport from source to sink during the vegetative growth (PHT1, PHT2 families)
A2 - preferential allocation of Pi to photosynthetic leaf cells
A3 - Reducing P transport from source to sink during reproduction stage (SPDT, PH01:2)

128
Q

What is an overview of remobalising P from cellular pools?

A

B1 - Phosphate recycling from vacuole
B2 - Pi liberation from organic P pools

129
Q

What is an overview of Pi liberation from organic P pools?

A

Membrane remodelling and liberating Pi from Lipid-P (LPA, LPC, LPD)
Phosphotases to liberate Pi from Pi-esters (PAPases, PPsPase)
Economically liberating and using Pi from Pi-esters (RNases, DNases
Quantifying the contribution of P fractions allocation to PUE

130
Q

What other form of phosphate that could improve efficiency?

A

Phosphite - [HPO3]2−
A few bacterial strains that are capable of oxidizing phosphite to produce phosphate but plants cannot.

131
Q

What is an overview of Transgenic Arabidopsis plants that express a phosphite oxidoreductase?

A

Transgenic Arabidopsis plants that express a phosphite oxidoreductase can use phosphite as a P source
A.t with ptxDAt-3,5,7 grow they can but WT can’t grow showing additonal herbcide function

132
Q

What is an overview of Transgenic tobacco plants that express a phosphite oxidoreductase when grown with weed Brachypodium distachyon?

A

In phosphite environments the tobacco grew well but the weeds did not
Weeds and tobacco grown together in normal soil saw weeds outgrow
Both seperately both grew well

133
Q

What is an overview of NUE vs PUE?

A

Soil mobility differs – NO3- mobile; phosphate and NH4 + immobile
Symbioses – bacteria and fungi
Root architecture and transport important
Need to match soil supply to crop demand
Measuring supply/demand – for ‘precision agriculture’

134
Q
A

3s2: Plant biotechnology (9 decks)

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