Professor Woo Taek Kim’s Biology Department Team Publishes Article in “Plant Cell” Korean researchers have unearthed the genes related to the drought stress and made the drought-tolerant plants using the genetic manipulation. Professor Woo Taek Kim’s research team in the Department of Biology, Yonsei University, demonstrated that PUB22 and PUB23 genes control the drought tolerance of plant. PUB22 and PUB23 proteins are ubiquitin E3 Ligases involved in protein degradation or processing of the protein modification through the attachment of ubiquitin to the target protein. This research team found that pub22pub23 double mutant plants that were created through the genetic manipulation of PUB22 and PUB23 genes were highly resistant to the severe drought stress compared to the wild type plants. The results of this study were published in the Plant Cell, the prestigious journal in the field of plant biology, on July 29, 2008. Before this study, the Yonsei research team exhibited that CaPUB1 genes in hot pepper were rapidly induced by the drought stress and CaPUB1-overexpressing transgenic plants were hypersensitive to drought stress. To further study the cellular functions of PUB E3 ubiquitin ligase with respect to drought tolerance, they isolated two genes in Arabidopsis, PUB22 and PUB23, over 50 percent similarity with CaPUB1. Wild type and PUB22- and PUB23-overexpressing transgenic plants were subjected to a dehydration treatment consisting of withholding water for 9 days. After rewatering for 3 days, wild type plants were able to survive and continued to grow 59%. By contrast, PUB22- and PUB23-overexpressor did not recover from the stress and died. The survival ratios of them were 3 to 12%. In addition, wild type and PUB22 and PUB23 mutant plants were not watered for 12 days and then rehydrated for 3 days. During this severe drought period, wild type plants were severely wilted, and <7% survived after watering. The survival ratio of pub22pub23 double mutant plants was 70%. These results indicated that over-expression of PUB22 or PUB23 increased sensitivity to dehydration, and mutations in these genes elevated tolerance to drought stress. "These results indicate that PUB22 and PUB23 genes control the plants response to drought stress and tolerance,” Professor Woo Taek Kim said. “Now, we are studying this research to apply for rice and for the ornamental plants."