The green revolution Flashcards
The steps of the green revolution
11,000-3,000 BCE (neolithic) -> Transition from huntergathering to agriculture
1940s-50s -> Semi-dwarf crops
- Lead by Norman Borlaug who studied wheat and identified that reducing height put more energy into the grain. (5-10% yeild increase)
- Also worked to improve disease resistance and bredth to growing conditions.
2015- present -> Precision breeding using technology
Another green revolution is required for food production to keep pace with population growth -> must improve yeilds to stop all land being taken over by farming.
Biology underlying dwarf plants
DELLA is a growth repressor that bind to the TF and inhibits growth.
Giberellin binds to GID1 leading to a conformational change allowing it to bind to Della and attract 26S proteasomes degrading DELLA and allowing transcription
RHT-B1 mutation means DELLA cannot be recognised by GID1 even in the presence of GA so growth is constantly repressed.
Key transformative technology: whole Genome sequencing
Genome seqeuencing is important to understand the position and identity of genes responsible for traits
Locating Resistant using RenSeq (resistant gene enrichment sequencing) Target Enrichment
1) EMS resistant plants and select susceptible plants
2) Resistant and susceptible genes are sequenced enriched (RenSeq) and sequences
3) analyses comparing DNA to locate resistance genes.
Example: EMS used to mutate plants resistant to stem rust and RenSeq Target Enrichment was used to locate the Sr22 resistant gene
Example: Study successfully applied RenSeq to the sequenced potato Solanum tuberosum clone DM, and increased the number of identified NB-LRRs from 438 to 755
locating genes resposible for key traits using genome wide association studies
Example: >700 Pisum lines sequenced and genome wide association studies used to locate genes responsible for pod shape
-> located on Chr11
large scale genome sequencing projects
Example: Darwin tree of life project
- 70,000 species of plants, fungi, animals and protists sequenced in britain and ireland to help understand biodiversity and guide conservation
Key transformative technology: Genetic modification
Foreign gene is transferred somewhere into the genome
Plant tranformation
- Gene of interest inserted into the Ti plasmid of agrobacterium tumefaciens
- Agrobacterium introduced into plant tissue and inserts DNA into host chromosome
- Transformed plant cells are induced to divide
- cells exposed to hormones leading to root and shoor formation
Examples: GM OSL
- Fish currently require high levels of Omega-3 fatty acids which they get from algae -> will not meet future demands in farmed fish
- Gene responsible for Omega-3 fatty acids production has been inserted into Oil seed rape
- Fish can be fed oil seed rape
Example: Bt maize/ cotton
- transgenic expression of Bt (Bacillus thuringiensis) protein in crops which kills insect gut cells and causes death
Example: purple tomatos
- Expresses anthocyanins leading to the purple colour
- Anti-oxidant and anti-carcinogenic properties
Example: sweet potatoes are a natural trangenic
Key transformative technology: Genome editing
more precise genome editing where genes can be precisely removed/ inserted
CRISPR/Cas9
- gRNA designed to bind to gene of interest
- Cas9 protein cuts DNA at target site
- DNA is repaired of replacement DNA is inserted (if donar template provided)
Example: Golden Bananas
- 2023 Golden bananas that rippen and don’t go brown were approved in the Phillapeans
- CRISPR used to silence gene producing polyphenol oxidase which turns banana brown (enzyme acitvated by ethylene produce in ripening)
Lack of crop diversity and the potential of diversifying
Small seleciton of crops are grown:
- 50% of world’s food calories come from four crops: wheat, rice, maize and sugar cane
- 75% of arable land in the UK taken up by three crops: wheat, barley and oilseed rape
Opportunities from growing underutilised crops.
- Increasing plant-based protein in human diet
- Introduce crops with higher resilience towards climate change and better suited for certain geographical locations
- May reduce need for fertiliser/chemical input
Challenges
- Low yield due to lack of domestication
- May contain anti-nutritional/toxic compounds
- Unpopular with farmers due lack of suitable machinery, low yield
- Introduction to consumers/legislation may be challenging.
Using genome modification and engineering to accelerate domestication: Physalis pruinose (Ground Cherry)
The ground cherry had not been domesticated efficiently:
o Indeterminate shoots
o Sympodial growth
o Single flowered inflorescence
o Bilocular fruit
They compared the ground cherry to the domesticated tomato to identify important domestication genes
SELF-PRUNING (SP)
-> SP editing leads to compact inflorescence and improved fruit set
CLAVATA1 (CLV1)
-> CLV1 editing increases floral meristem size and fruit locule number
-> It is a negative regulator so CRISPR used to knock it out
Understanding domestication of one crop leads to insights about other crops.
Overview
Stages of the gren revolution
- transition to agriculture
- dwarf plants
- The rise of gene technology
-> gene sequencing
-> Genome modification
-> gene editing
Few plants are currently utilised -> expanding may be beneficial
In order to keep pace with population increase another green reovlution is required.
