Salty soil is a growing threat to crops worldwide. Hotter, drier weather has increased evaporation rates, drawing moisture from the soil and leaving behind concentrated mineral salts. At the same time, water shortages are forcing farmers to irrigate using water from lower-quality, saline or recycled sources. Scientists estimate that around half of the world’s irrigated farmland is now affected by salinity to some degree.
A new study from Washington University in St. Louis reveals how a plant’s internal clock helps it to respond to dangerous salts in its environment. Understanding how plants time their defenses against salt could eventually help scientists develop crops that hold up better against salt stress.
The research, published Oct. 14 in Science Advances , was led by biologist Xuehua Zhong , the Dean’s Distinguished Professorial Scholar in WashU Arts & Sciences, and WashU postdoctoral fellow Wenwen Tian , an expert in circadian biology.
Biologists already knew that a plant’s internal clock and its stress responses were connected — but not how the clock actually reaches the genes that protect the plant when trouble hits.
The link is surprisingly physical, Zhong said.
“When a plant senses salt, a clock protein clusters into tiny droplets inside the nucleus, which frees protective genes to switch on,” Zhong said. “Because the clock protein is part of this switch, the plant’s stress defenses are tied to its sense of time.”
Among the researchers’ findings:
These findings open novel ways to think about building more resilient crops, the scientists said. Because TIC acts as a salt-responsive switch, it could become a target for breeding or gene editing. The new research also shows that plants cope with salt best when their internal clock matches their environment, a finding that suggests that tuning crop clocks could improve stress tolerance, Zhong said.
“The clock directly shapes stress responses,” said Zhong, who also credited WashU undergraduate researcher Xinheng Lyu and visiting Stanford undergraduate student Grace Qian for making important contributions to this research as co-authors. “The same stress can produce different gene expression outcomes depending on when it occurs.”
Funding: Zhong’s research was supported in part with grants from the National Institutes of Health (R35GM124806) and the National Science Foundation (MCB-2448006), as well as other federal funding .
Science Advances