Abstract:

【Objective】 The objective of this study is to isolate ROP (Rho GTPase of plant) gene from Medicago truncatula and analyze its expression pattern in order to further investigate the function of ROP in symbiotic interaction. 【Method】 Through analysis of comparative genomics, MtROP5 gene in M. truncatula was isolated by RT-PCR. Using semi-quantitative RT-PCR, the expression level of MtROP5 gene was detected in different tissues of M. truncatula, and real-time quantitative RT-PCR was used to detect the expression levels of MtROP5 gene in inoculated root which was infected by Sinorhizobium meliloti Rm1021 during the 72 hours post-inoculation. 【Result】 MtROP5 gene with a complete open reading frame of 826 bp encoding a peptide of 197 amino acid residues was isolated from M. truncatula. Results of sequence analysis showed that MtROP5 contains the typical structures of ROP GTPase family. Homologous comparison with some plant ROPs indicated that MtROP5 shared high similarity with other plant ROPs. Expression analysis of RT-PCR showed that MtROP5 gene expressed in root, stem, leaf, flower, nodule, especially higher expression in stem and flower, next in root and nodule, and the expression level of MtROP5 gene in leaf was lower. Compared with the expression level of MtROP5 gene in uninoculated root, the expression level of MtROP5 gene was up-regulated at the different stages (0 to 72 hours) post-inoculation. 【Conclusion】 A small GTPase MtROP5 gene in M. truncatula was obtained. MtROP5 gene may involve in the regulation of signal transmission that occur at early stage of symbiotic interaction between legume plant and Rhizobium.

Key words: Medicago truncatula, small G protein, ROP, gene clone, expression analysis