AG1 gene plays an important role when rice seeds survive underwater

A gene was identified to help rice seeds to survive when grown underwater. The study was published in the leading scientific journal Nature Plants by A team of scientists from the University of California, Riverside and the International Rice Research Institute (IRRI), the Philippines. The study shows that the gene controls the availability of sugar to a growing seed shoot—especially when under flooded conditions.
"The seed of rice is unusual among crops because it can germinate and grow into a young plant that can capture light energy even when the entire process occurs underwater," said Julia Bailey-Serres, one of the paper's authors and a professor of genetics at UC Riverside. "The gene identified—the AG1 gene—helps in this process by allowing energy reserves that are in the seed to be efficiently moved to the growing shoot. The seed planted underwater grows into a seedling that can escape a shallow flood."
There was a gene called SUB1A discovered previously to enable rice plants to survive complete submergence due to a seasonable flood. But this new gene is opposite of that. Bailey-Serres says that Plants with SUB1A essentially hibernate when they are underwater; a situation where energy reserves are safeguarded.
AG1 creates an 'all or nothing' escape mechanism that tricks the seed into thinking that more sugar should be given to its shoot—the plant part that grows into stems and leaves—so that the seed underwater is able to more quickly grow and reach the surface of the water. The mechanism can work up to a water depth of 10 cm and can get 'activated' as soon as the seed is sown underwater.
This gene is one of a family of 13 genes in rice. Other family members are shown to help to move suger from leaves to the young developing seed in fertilized flowers. The important gene is supposed to tell the cell that it does not have enough sugar—keeping the tap open for more to be moved from the seed to the growing shoot.
AG1 works well on moderate stress conditions. When we combined it with the SUB1A gene in the same genetic backgrounds it worked well, although they have opposing mechanisms. However, in some severe stress conditions, AG1 alone is not sufficient. It needs some additional quantitative trait loci (QTLs) or genes that complement the AG1 mechanism.
There is another question they are faced with - Whether seed can be directly seeded underwater – requiring the escape strategy – can also carry the SUB1A gene for submergence tolerance. There are more to be investigated to find the answer.
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