Study On WOX Genes Functions In Rice Apical Meristem

Apex development and lateral organs differentiation in higher plants are definitely pivotal events in plant developmental biology,and also determine the morphological pattern of crops and economic plants.Rice is one of the most important food crop,and a model plant of the grass family for investigating apex development.Contrasted with the dicot Arabidopsis,rice has much uniqueness in its tissue and organ development process.Apex development is controlled by many factors as well as their interactions,such as genes of,plant hormones and environmental factors including temperature,light,abiotic stress etc.WOX genes are specific to plants and play key roles in Arabidopsis organ development,but little is known in rice.The present study isolated and characterized WOX genes.Their functions in rice apex development were clarified by direct and reverse genetic strategies.The main results are as follows:1.A total of 8 genes belonging to WOX family were identified in rice genome. Transgenic vectors designed for over-expression and RNAi surpression were also constructed and used to transform an Japonic rice variety Zhonghual 1.2.Expression profile analysis of 10 genes in different organs and tissues of Minghui63 variety by Microarray were performed.The results showed that their expression is tissue and/or organ specific,Rice WOX family genes are involved in apex development.3.Subsequent studies were focused on OsWOX11,a member of WOXfamily. Results of RT-PCR,in situ hybridization and OsWOX11::GUS or OsWOX11::GFP fusion showed OsWOX11 is expressed in emerging crown roots and in cell division region of root and shoot meristem,and involved in Rice crown root development and growth.4.Data of OsWOX11 over-expression,RNAi knock-down and T-DNA insertional mutation showed that OsWOX11 participates in Rice crown root development.Loss of OsWOX11 function and RNAi transgenic plants displayed aberrations in root development.Over-expression of OsWOX11 in transgenic plants induces a large root system and ectopic shoot-bome root at almost every nodes and the base of floret.All these shows that OsWOX11 plays an important role in rice crown bome root development.5.Plant hormone responsive elements,such as Auxin,Cytokinin,Ethylene,and ABA,were found in the promoter of OsWOX11.These hormones treatment can rapidly induce OsWOX11 expression.OsWOX11 regulate hormone responsive factors gene up- or down-expression in OsWOX11 transgenic plants and mutation.All of these showed that Os WOX11 is a hormone responsive gene.6.Expression of genes involved in auxin,cytokinin and ethylene synthesis, response and transport,is affected in paints of OsWOX11 over-expression,RNAi knock-down and loss of function mutations.7.Electrophoretic Mobility Shift Assay(EMSA) revealed OsWOX11 protein regulates OsRR2 expression directly in vitro. 8.OsRR2 expression profiling clarified that OsWOX11 interactively regulate OsRR2 expression during crown root growth,elongation and development.9.Study oftransgenic plants expressing OsWOX11-GFP and OsWOX11-GR and immuno-precipitation experiment showed that OsWOX11 is able to interact with the OsRR2 in vivo.