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The GRAS gene family is a class of plant specific transcription factors, which were reported playing important roles during plant development and lightsignal transduction pathway, and other physiology processes. 33 GRAS family genes were identified in Arabidopsis genome.In this study, 35 corresponding peptides were chosen from TAIR database (http://www.arabidopsis.org). The sequences were aligned by ClustalW software,and phylogenetic tree was constructed by MEGA3.1. The tree showed that fiveclusters were formed. SCL4, SCL7, SCL18, SCL23, SCL26 and SCL28 belong to one cluster, SCL9, SCL11, SCL14, SCL30, SCL31 and SCL33 was anothe-r cluster, other clusters were SGR7, RGA2, RGA1, RGL1, RGL2 and RGL3, SCL1, SCL5, SCL8, SCL13, SCL21 and PAT1, SCL6, SCL15, SCL22 and SC-L27, respectively.Functional genomics and bioinformatics approaches were conducted to ident-ify the GRAS family genes responding to osmotic and drought stresses throug-h Arabidopsis GeneChip data mining and gene function prediction. Through Arabidopsis ATH1 GeneChip data mining related to drought stress, the probese-ts of 27 GRAS family genes was found . GRAS Genechip data responded to drought stress was analysed using Hiera-rchical Cluster method, and result was showed by Treeview software. Ten GR-AS genes SCL1, SCL3, SCL5, SCL8, SCL9, SCL11, SCL13, SCL14, SCL31 and SCL33 were induced by drought stress or osmotic stress in shoots. Amon-g them, four genes including SCL8, SCL11, SCL13 and SCL31 were induced by drought stress and osmotic stress at the same time. While Genes SCL1,SC-L5,SCL6,SCL8,SCL9,SCL13,SCL14,SCL15,SCL26 and SCL33 were induced bydrought stress or osmotic stress in roots.Expression analysis on the Arabidopsis Genechip data responded to drought stress in shoots and roots showed that gene SCL11 was induced only in the shoots. The signal intensity ratio of drought treated shoots and the control sho-ots was 2.73, 0.5h aft er the plants were treated. The ratios were 6.69 and 4.02 for gene SCL13 in shoots and roots respectively. And it was 3.94 in roots fo-r gene SCL15.According to the characters of GRAS family genes responding to drought stress and their expression in tissues, the role of SCL15 in the family was vali-dated under drought stress by its T-DNA mutant. T-DNA mutant was screene-d and identified using the specific primer for SCL15 and for insert sequence. After water dehydration for two or three weeks, SCL15 Mutant kept green, wh-ile the wild plants were withered and leaves turned yellow. The difference of the phenotype between wild and mutant type of SCL15 indicated that the grow-th of SCL15 mutant need less water, and indirectly resistant to drought stress. It showed that SCL15 might negatively regulate the down stream genes. This study gave us a new understanding on the molecular mechanism of GRAS fa-mily genes involved in the drought stress.
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