Cloning and expression analysis of small GTPase MtROP9 gene in Medicago truncatula.

【Objective】The objective of this study was to isolate ROP(RhoGTPase of plant) gene in Medicago truncatula and analyze its expression pattern in order to further investigate the function of ROP gene in the process of symbiotic interaction between host legume plant and Rhizobium.【Method】Based on the conserved sequences of 11 ROP proteins in Arabidopsis,homologous gene in Medicago truncatula was isolated by RT-PCR.The sequence analysis of MtROP9 was carried out using the method of bioinformation.Using the method of Semi-quantitative RT-PCR,the expression levels of MtROP9 was detected in different tissues and in inoculated root on different time of post-inoculation.【Result】A full-length 947 bp cDNA sequences of MtROP9 gene that coded 209 amino acids were isolated from root of Medicago truncatula.Results of sequence analysis showed MtROP9 contained the typical structures of ROP GTPase protein.Homologous comparison with some plant ROPs indicated that MtROP9 shared high similarity in amino acid sequence with AtROP9,OsRac2,VvROP9,ZmROP6 and ZmROP7 respectively.Spatial and temporal patterns of MtROP9 gene were approved through detected expression levels of MtROP9 in different tissues and in inoculated root by Rhizobium.MtROP9 was expressed preferentially in root and flower,and showed lower expression levels in stem and nodule.But MtROP9 almost could not be detected in leaf.Expression of MtROP9 could be induced by inoculation of Rhizobium.MtROP9 gene displayed a varied expression level in inoculated root during different time of post-inoculation by Rm1021.【Conclusion】A small GTPase MtROP9 gene in Medicago truncatula was obtained.MtROP9 gene may involve in the regulation of signal transduction that occurred on early stage of symbiotic interaction between legume plant and Rhizobium.