4. Adaptive response to Flooding Flashcards
Structure of the lecture
- Major adaptive responses to flooding
- Breeding waterproof crops
- Synthetic biology approaches
What are the 6 major adaptive strategies to flood stress?
1
- Anaerobic germination
- Submergence-induced heterophylly
- Leaf gas films
- Fast elongation to end subemergence
- Aerenchyma and ROL barriers
- Adventitious roots
How can anaerobic germination be used to overcome flood stress?
1.1
Does not need oxygen for seeds to germinate.
For example, this is seen in rice. When in normoxic conditions, plants will induce amylases in the aleurone via GA, which leads to germination. Which in anoxic conditions, rice is able to generate a different alpha-amylase, which leads to anaerobic germination
How can submergence-induced heterophyllu be used to overcome flood stress?
1.2
Means the change in leaf shape
Heterophylly is caused by light quality (can be a product of turbidity), humidity and temperature. All of these factors regulate gibberellins, which controls leaf development
For example, in rice. Several rice from different genera are able to display alternative leaf morphologies upon submergence. This might include the loss of stomata, and smaller leaf intake to limit water intake and result in less gas ecahnge.
How can leaf gas films be used to overcome flood stress?
1.3
Hydrophobic surface that is generated around the lead to improve underwater photosynthesis and prevent gas exchange
For example, in Kinmaze rice, which has strains with a drp7 mutation that increases leaf hydrophobicity and can improve underwater photosynthesis
How can fast elongation be used to cope with flood stress?
1.4
For example, deepwater rice varities show rapid internode elongation when submerged, and can grow metres high.
The opposite is seen in Sub1 rice varieties, which enter a state of ‘hibernation’ under stressed conditions and show immense potential for breeding high yield, flood-safe crops
Can lead to low yield and induce lodging (which is when the plant topples over when water levels fall, which can lead to pathogen invasion)
How can aerenchyma and ROL barriers be used to cope with flood stress?
1.5
Shoot and root tissues can develop these hollow cavities that enhance O2 transfer from aerial tissues to submerged ones
Aerenchyma are paired with barriers for ROL (Radial Oxygen Loss), such as suberin to be fully effective
How can adventitious roots be used to overcome flood stress?
1.6
These roots will form from the stem, and sustain aeration, nutrient acquisition and growth during flooding
What are two major ways that we can breed waterproof crops?
2
- Induction of the sub1 locus to breed waterproof rice
- GWAS, which can be used to create flood resistant barley strains
How can the sub1 locus be used to breed waterproof crops?
2.1
Sub1 locus is found in wild accessions of rice in Pakistan
Contains 8 genes, 3 of which belong to the ERFVII family (Sub1A, B, C).
Sub1A induces DELLA genes, which repress gibberellin signalling, thereby inhibiting growth
Growth is therefore being prevented, and energy is saved, and the plant will not grow until submergence end
This can be combined with high yield crop individuals (e.g., Swarna) via genome editing techniques
This has the potential to create high-yield, flood resistant crops
How can GWAS be used to breed flood-resistant crops?
2.2
Flood resistant barley strains
The Laccase gene is responsible for lignin polymerisation, and is differentially expressed in flood tolerant and sensitive barley varieties
This correlates to deletions in the promoter region
Thinner layers of lignin may increase oxygen penetration, and enhance germination capacity
This can be used for selective breeding, ro the genetic engineering of barley for flood resistance
What are 3 different synthetic biology approaches that can be used to create adaptive responses to flooding?
3
- Manipulation of oxygen tolerance
- Exploitation of the N-degron pathway
- Rewiring existing alpha-amylases
How can we manipulate oxygen tolerance to create flood tolerance?
3.1
Synthetic biology approach
Engineering of PCO enzymes that leads to more rapid priming and stabilisation of ERFVII molecules
This can be done via structure-guided rationale design, or random mutagenesis, or gene insertion via plasmids
How can alpha amylases be rewired to create adaptive responses to flooding?
3.3
Rewiring alpha-amylases to be activated in anoxic conditions. This would allow for anaerobic seedling germination.
Could use genome editing to alter the alpha-amylase GAMYB
