Cloning And Functional Analysis Of Rice O_sYAD Gene

Stomata, the specialized structure in the epidermis of stem and leaf, consisting of two guard cells, play important role in transpiration and gas exchange between plants and environment. The distribution pattern of stomata in monocots, such as rice and maize, differ from that in dicots, such as Arabidopsis, with the former being in parallel with linear vein while the later being random. Furthermore, stomata density (the ratio of stomata to total pavement cell) is under complex regulation.With respect to the developmental process of stomata,a protodermal cell undergoes one to three rounds of asymmetric divisions and a symmetic division to develop into a stomata, a process faciliated by positively-acting bHLH transcription factors, such as SPHC, MUTE and FAMA, etc. Stomatal development is negatively regulated by MAPK cascade, a conserved pathway in the whole eukaryotic world. MAPKs regulate many physiological aspects of plant, such as anti-pathogen response, anti-abiotic stress and hormonal signal transduction, etc. YDA, a MAPKKK(MAPK kinase kinase),was found to negatively regulate stomatal development. Stomata are excessively produced in yda loss-of-function mutant, while consititutive expression of full-length YDA or N-terminal deletion variantΔN-YDA leads to complete loss of stomatal production. In this study, two genes in rice encoding orthologs of AtYDA, namely OsYDA1 and OsYDA2, were cloned and introduced into Arabidopsis and rice, respectively.The results showed that the overexpression of the two genes results in increased shoot branching, decreased stomatal index in cotyledon and true leaf and reduced water-loss rate in Arabidopsis. The ectopic expression of the two genes leads to significant alteration of stomatal distribution in rice. Taken together, the results indicate the conserved function of YDA in monocots and dicots.