Protein destruction helps plants enter a different life stage

As a seed awakens and begins to sprout, it must make a decision: does it have everything it needs to grow, or should it wait for better conditions? The choice rests on the presence or absence of one protein, ABI3, and new research from the laboratory of Nam-Hai Chua, Ph.D., at Rockefeller University provides insight on how ABI3’s presence is controlled.

Controlling the levels of ABI3 protein may eventually help farmers save crops in times of drought and heat, where higher levels of ABI3 will prevent plants from sweating out much-needed water through their pores, called stomata, or in times of excess rain, where higher levels of ABI3 can prevent the seed on the plants from germinating and allow enough time for harvest.

“Abscisic acid is a molecule that, through its activation of ABI3, helps the plant deal with stress,” says Xiuren Zhang, Ph.D., co-first author of the paper. “For instance, in a time of drought, ABI3 will prevent the newborn plant from sprouting and growing, making it wait until the conditions are right.”

But when the conditions are perfect, the ABI3 protein needs to be removed, or it will prevent the plant from growing and flowering. Zhang and co-first author Virginia Garreton, Ph.D., discovered that a protein called AIP2 can promote the destruction of ABI3 proteins, allowing the plants to grow and flower.

“It is important to understand the signaling mechanisms in this stress response pathway, which is the same in the majority of plants,” says Chua. “These findings not only provide new insights into the mechanism of abscisic acid signaling and ABI3 regulation, but they also have the potential application for the development of stress-tolerant plants.”

The study, reported in the July 1 issue of Genes & Development, was supported by The Department of Energy.