Identification Of Rice BRX Family And Preliminary Function Analysis Of Gene OsBRX4

Root is an important plant organ that has multiple functions including acquisition and fixation of water and nutrient, perception of environment changes in soil, and synthesization of phytohormone. BRX family are novel transcription factors, and the key member BRX (Brevis Radix) controls cell proliferation and elongation of root through mediating the signaling of BR and auxin signaling pathway in Arabidopsis. The root system of rice (Oryza satva L.), one of the most important crops worldwide, has significant functions in enhancing abiotic stress-tolerance and yield potential. Considering the important role of BRX genes in root growth in Arabidospsis, it is meaningful to study the BRX family of rice both on the function and application of the genes in this family.There are four aspects of contents in this research: 1, Identification and analysis of BRX family members in rice; 2, Expression profile analysis of this family in different tissues and under abiotic stress and phytohormone treatment; 3, Construction and genetic transformation of overexpression vectors of OsBRX1, 0sBRX3 and 0sBRX4, and characterization of the overexpression lines; 4, Identification and overexpression of stress-induced zinc finger genes.The main results are as follows:1. Six members of rice BRX family were identified and analyzed for their gene structures and phylogenetic relationships. The inton-exon structures of rice BRX family members are conserved. There are evolutional overlapps among members in rice, bryophytes, gymnosperm and monocotyledon.2. Tissue expression profiles showed that there are four members specifically expressed in young panicle. Unexpectively, no member was found to be specifically expressed in root.3. Expression level analysis of BRX family members under the treatments of drought, salt and cold indicated that five genes are responsive to at least one of the treatments.4. Differential expression of BRX family was also detected under BR and auxin treatments. The results showed that OsBRX1 and OsBRX4 are up-regulated by BR and auxin, suggesting that BRX family may involved in both BR and auxin signaling pathways.5. The primary root length of OsBRX4-overexpressing lines are 23%-26% longer than that of the wild type. Meanwhile, the OsBRX4-overexpressing lines are more sensitive to auxin, suggesting that OsBRX4 may be involved in the auxin-mediated regulation of primary root growth in rice.6. The overexpression vectors of 14 stress-inducible zinc finger genes were constructed and 7 of them have been transformed into rice, which will be tested for stress resistance and /or root growth in future studies.