'Fountain of youth' for leaves discovered

What plant scientists call senescence, consumers experience as wilted produce and overripe fruit. A team led by Cornell horticulture professor Su-Sheng Gan has identified an enzymatic fountain of youth that slows the process of leaf death, a discovery that lays the foundation for the genetics of freshness.

In a series of experiments using the plant Arabidopsis thaliana, Gan and colleagues discovered a key regulator – S3H – that acts as a brake on the process of leaf death. When its levels are low, leaves senesce early; when it is present in high levels, it results in longer leaf longevity.

"It was serendipity – we weren't actually looking for this gene, but it turned up in an earlier survey of genes involved in leaf senesce," Gan said. "When we characterized it, we found more than we were looking for: a key step in the plant's pathway for controlling senescence that had been eluding scientists."

The study provides insight into a highly regulated process with many molecular steps. According to Gan, plant senescence is estimated to involve 10 percent of genes in the genome. Plants use an expedited 'hypersensitive' process to thwart pathogens by sacrificing infected cells to protect the surrounding healthy tissues. The slower version of the cell-dying process is what lights up hillsides in autumn: botanical recycling that ensures the nutrients and proteins in the leaves have been stowed for use in next spring's flowers, seeds and leaves.