Crops engineered to stay green longer could produce more food for growing global population

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A team of Clemson University scientists has achieved a breakthrough in the genetics of senescence in cereal crops with the potential to dramatically impact the future of food security in the era of climate change.

The collaborative research, which explores the genetic architecture of the little understood process of senescence in maize (a.k.a. corn) and other cereal crops, was published in The Plant Cell …. Rajan Sekhon, a plant geneticist and an assistant professor in the College of Science’s department of genetics and biochemistry, is the lead and corresponding author of the paper ….

“Senescence means ‘death of a cell or an organ in the hands of the very organisms it is a part of,’ ” Sekhon said. “It happens pretty much everywhere, even in animals. We kill the cells we don’t need. When the weather changes in fall, we have those nice fall colors in trees. At the onset of fall, when the plants realize that they cannot sustain the leaves, they kill their leaves. It is all about the economy of energy.”

As a result, the leaves die off after their show of color. The energy scavenged from the leaves is stored in the trunk or roots of the plant and used to quickly reproduce leaves next spring. This makes perfect sense for trees. But the story is quite different for some other edible plants, specifically cereal crops like maize, rice and wheat.

“These crops are tended very carefully and supplied excess nutrients in the form of fertilizers by the farmers,” Sekhon said. “Instead of dying prematurely, the leaves can keep on making food via photosynthesis. Understanding the triggers for senescence in crops like maize means scientists can alter the plant in a way that can benefit a hungry world.”

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“If we can slow senescence down, this can allow the plant to stay green — or not senesce — for a longer period of time,” Sekhon said. “Plant breeders have been selecting for plants that senesce late without fully understanding how senescence works at the molecular level.”

These plants, called “stay-green,” live up to their name. They stay green longer, produce greater yields and are more resilient in the face of environmental factors that stress plants, including drought and heat.

“One of the most remarkable discoveries was that sugars appear to dictate senescence,” Sekhon said. “When the sugars are not moved away from the leaves where these are being made via photosynthesis, these sugar molecules start sending signals to initiate senescence.”

However, not all forms of sugar found in the plants are capable of signaling. One of the genes that Sekhon and colleagues discovered in the study appears to break complex sugars in the leaf cells into smaller sugar molecules — six-carbon sugars like glucose and fructose — that are capable of relaying the senescence signals.

The genes identified in this study are likely performing the same function in other cereal crops, such as rice, wheat and sorghum. Sekhon said that the next step is to examine the function of these genes using mutants and transgenics.

“The ultimate goal is to help the planet and feed the growing world. With ever-worsening climate, shrinking land and water, and increasing population, food security is the major challenge faced by mankind,” Sekhon said.

Read full, original article: Genetic breakthrough in cereal crops could help improve yields worldwide

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