Tropes

futurity_sci_tech 00953.txt

#Could this gene make leafy greens last longer? Scientists have identified the process in plants that controls how quickly leaves die which may lead to lettuce that stays fresh in the fridge a little longer. In a series of experiments using the plant Arabidopsis thaliana researchers discovered a key regulator S3h that acts as a brake on the process of leaf death which is known as senesce. 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 says Su-Sheng Gan professor of horticulture at Cornell University. 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. At the start of that pathway is salicylic acid precursor of the active ingredient in aspirin which is used by plants as a hormone to trigger development and to fire up a response to a pathogen attack. The gene product they discovered breaks down salicylic acid effectively silencing the molecular command to die. In addition to affecting the timing of leaf death it also affects its rate: While normal plants take more than nine days for a leaf to progress from living green to yellow plants without the gene yellowed in fewer than three days. Published in the Proceedings of the National Academy of Sciences the study provides insight into a highly regulated process with many molecular steps. 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. What we have found is the convergence point between the slow and fast death systems Gan says. When the plant starts to accumulate salicylic acid it turns on S3h which then acts as a brake on the process by breaking down the salicylic acid giving the plant enough time to recycle all the reusable parts. In the current study the increase in leaf longevity was significant but was tallied in days. Gan expects further research to enable the delay of senescence for weeks. In the current transport and storage-based food system senescence after harvest whittles away at fruit and vegetable quality. Gan envisions applications that will produce leafy greens that stay fresh floral bouquets that last longer and crops that keep their nutrients with an extended shelf life and less postharvest loss. Manipulating this pathway also holds promise for bigger harvests and healthier plants. Much of the progress plant breeders have made in improving plant yields is actually due to delaying leaf senescence Gan says. You need long-lived green tissue to support the production of fruits vegetables and seeds so senescence limits the yield of many crops. His lab group is already working with other genes in the salicylic acid pathway including a master regulator gene with promising results. When they switched the gene off using molecular tools soybean yields were increased by up to 44 percent t

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