Auxin regulates plant growth and development by altering the expression of diverse genes. Among these, the genes of Aux/IAA, SAUR, and GH3 classes have been extensively studied in dicots, but little information is available on monocots. We have identified 12 members of GH3 gene family in rice using sequences of full-length cDNA clones available from KOME and analysis of the whole genome sequence of rice. The genomic organization as well as chromosomal location of all the OsGH3 genes is reported. The rice GH3 proteins can be classified in two groups (groups I and II) on the basis of their phylogenetic relationship with Arabidopsis GH3 proteins. Based upon the sequences available in the database, not a single group III GH3 protein could be identified in rice. An extensive survey of EST sequences of other monocots led to the conclusion that although GH3 gene family is highly conserved in both dicots and monocots but the group III is conspicuous by its absence in monocots. The in silico analysis has been complemented with experimental data to quantify transcript levels of all GH3 gene family members. Using real-time polymerase chain reaction, the organ-specific expression of individual OsGH3 genes in light- and dark-grown seedlings/plants has been examined. The transcript abundance of nearly all OsGH3 genes is enhanced on auxin treatment, with the effect more pronounced on OsGH3-1, -2, and -4. The functional validation of these genes in transgenics or analysis of gene-specific insertional mutants will help in elucidating their precise role in auxin signal transduction.
生长素通过改变多种基因的表达参与调控植物的生长发育。在这些基因中，Aux/IAA、SAUR和GH3类基因在双子叶植物中被广泛研究，但是单子叶中可以获得的这些基因的信息还很有限。通过分析KOME数据库中的全长cDNA和水稻全基因组序列，作者从水稻中鉴定到GH3基因家族的12个成员。本研究报道了这些OsGH3基因在基因组上的组织结构和染色体位置。根据与拟南芥GH3蛋白系统发生的关系，水稻GH3蛋白可以分为两组（I组和II组）。根据数据库中获得的序列，水稻中没有个属于III组的GH3蛋白。对其他单子叶植物EST序列的深入分析，发现双子叶和单子叶植物GH3基因家族是高度保守的，但是III组基因在单子叶植物中显著缺失。作者对所有鉴定到的GH3基因家族成员的转录水平进行了分析。通过real-time PCR对光下和暗中生长的水稻幼苗/植株OsGH3基因的器官特异性表达进行了检测。生长素处理能够使几乎所有OsGH3的表达丰度提高，其中以OsGH3-1, -2 和-4 的增加最为显著。对这些基因的功能验证或对基因特异的插入突变体进行分析，将有助于阐明这些基因在生长素信号传导中的作用。