Whole Genome-wide Expression Profiles Of Differential Genes In Leaves Of Rice Seedlings Responsive To Exogenous Nitric Oxide Application

Nitric oxide(NO) is a kind of gaseous hormone with free radical characteristics. NO is highly reactive, can rapidly diffuse and permeate cell membranes. Plants not only react to exogenous NO, but can also produce quantity of endogenous NO. In recent years,accumulating evidence has revealed that NO plays an important role in the growth and developmental processes as well as responses to different stresses in plants. Based on high-throughput DNA chip technology, gene expression profile analysis has been widely applied to elucidation of mechanisms underlying plant stress responses, and has made a great progress up to date. However, rice gene expression profiles under NO treatments has not been reported yet.Herein, we investigated the expression patterns in leaves of rice seedlings at 1(T1), 6(T6) and 12 hours(T12) after exogenous NO treatments by using cDNA microarray(Agilent rice oligo microarray, 4×44 k) at a genome-wide scale. Totally, 3852 differently expressed genes, whose expression was more than three-fold change at one time point compared with the control(0 h, T0), were identified. 1195 NO-responsive genes, whose expression was more than three-fold change at least two time points among the three time points compared with T0,were identified. Prediction of gene function and analysis of metabolic pathways showed that NO-responsive genes were mainly involved in stress responses, redox, secondary metabolism,biosynthesis of physiological processes and so on. The results of microarray hybridization were largely consistent with those of quantitative real-time PCR, verifying the validity of microarray hybridization. The study provides theoretical foundation for elucidation of the mechanisms underlying the physiological action of NO in plants.Both signal molecule NO and WRKY transcription factors are involved in many physiological processes such as defense against stresses, development and metabolism in plants. To explore whether NO signaling might be involved in the regulatory functions of WRKY proteins, the expression profiles of rice WRKY gene family under the treatment of NO application was specially focused and systematically analyzed. Totally, 32 differently expressed WRKY genes, whose expression was more than two-fold change at one time point compared with T0, were identified. These WRKY genes were mainly distributed over Groups I and II, among which 75% of IIa and 45.6% of IId subgroup members were differently expressed upon the NO treatments. Moreover, 15 identified NO-responsive WRKY genes,whose expression was more than two-fold change at least two time points among the three time points compared with the control, exhibited an early(1 h) responses to the NO treatments, and most of them(64.2%) were continually up-regulated. Prediction of gene function revealed that the NO-responsive WRKY genes were mainly involved in cellular process, metabolic process and response to stimulus of biological process, and transcription regulator activity and binding of molecular function. The analysis of metabolic pathwaysshowed that WRKY24 was involved in plant-pathogen interaction pathway. These findings suggest that NO signaling might be involved in the regulatory functions of WRKY transcription factors, and provide a basis for further functional research for these differentially expressed WRKY genes.