NEGATIVE REGULATIONS PLAY A ROLE AS “KEYSTONES” FOR THE CONTROL OF PHYSIOLOGICAL ACTIVITIES IN PLANTS

Masaru Ohme-Takagi

Graduate School of Science and Engineering, Saitama University, Saitama 388-8570, Japan

Abstract

It becomes evident that negative regulations play a key role on the control of various physiological responses in plants, such as for hormones, environmental stresses, rhythms, and maintenance of meristems. Negative regulations are found various levels of gene expressions through genome to proteins. Those are epigenetic regulation, transcriptional repression, and degradations of mRNAs and proteins. We have developed a novel gene silencing system using an artificial transcriptional repressor, called Chimeric REpressor Gene-Silencing Technology (CRES-T), in which a transcription factor that is converted into strong repressor by fusion with the plant specific repression domain (SRDX), suppresses the expression of target genes dominantly over the activation activity of endogenous and functionally redundant transcription factors, resulted in the induction of phenotype similar to loss-of-function of the alleles of the gene for transcription factors. Using this CRES-T system, we succeeded identification of the chimeric repressor expressing plants that exhibit tolerances to various environmental stresses, such as drought, salt, heat, acid and low nutrient, respectively. Interestingly, a large number of genes that are involved to the tolerant phenotypes were revealed to be upregulated in those plants, showing the presence of negative factors that suppress the genes related to stress responses. We show here that the modification of negative regulars is effective and powerful strategy for the manipulation of plant traits than simple overexpression.