QC And Stem Cell Specification In Rice Root

Root is a very important organ of plants, and it plays a significant role in nutrients absorption, plant development and stress resistance. Plant root QC(quiescent center) and stem cells hold the key to plant root architecture and development, thus the study of the plant root QC and stem cell specification is a basic step to understand the process of plant root development. In Arabidopsis, PLT genes are required for QC and stem cell specification which have a strong impact on root development. Compared to the progresses in Arabidopsis, root research in rice has largely lagged behind. As the most important food crop in China, rice has attracted increased attention in recent years. Research on rice root development, in particularly QC and stem cell specification shall be of great importance for improvement of rice production.Basic on the researches of PLT genes in Arabidopsis (AtPLT), in this study, we used both forward and reverse genetics approaches which include molecular genetic, developmental biological and bioinformatic strategies to study rice root stem cell niche related genes, aiming at identifying novel factors of rice root architecture and stem cell niche specification. The results of this study may be applied to modify rice root and produce higher yield.The main results are as follows:1) Bioinformatics analysis:through bioinformatic approaches, we compared the amino acid sequences of 12 PLT genes in rice (OsPLTs) with their homologous genes in Arabidopsis, and generated a phylogenetic tree of these genes. Additionally, we analyzed the OsPLTs expression profiles and their co-expression patterns from two microarray databases. Amino acid sequence comparison display that all the OsPLTs share high sequence homology with AtPLTs, and all of these genes contained two AP2 domains. Phylogenetic tree analysis results suggest that OsPLT2、OsPLT12 and OsPLT9 shared high homology among all the OsPLTs. Based on the gene expression profiles from two microarray databases, OsPLT3、OsPLT7 and OsPLT9 showed high gene expression level in rice root compare with other OsPLTs. Co-expression analysis indicates that OsPLT7 co-expresses with 4 other OsPLTs, whereas both OsPLT3 and OsPLT9 co-expresses with 3 other OsPLTs.2) Study on OsPLTs expression profiles:successful construction and transformation of OsPLT7 and OsPLT11 promoter-reporter vectors into rice allowed us to use DIC (differential interference microscope) to directly observe expression profiles of OsPLT7 and OsPLT11 by GUS staining in different developmental stages. Our observation indicate that OsPLT7 and OsPLTll specifically expressed in QC and stem cells in rice root which share high expression similarity with AtPLTs.3) Screen of rice T-DNA insertion mutant library:using forward genetics strategy, we screened the rice T-DNA insertion mutant library which was generated in the national plant gene research center, Huazhong Agriculture University. Through stereomicroscope and DIC observation of GUS-stained root and the root resin slices, we found 24 stable GUS staining lines. Among them, we discovered 3 candidate genes which may related to QC and stem cell specification in rice root by flanking sequence isolation.