Abstract:

【Objective】 The function of MtROP5 in Medicago truncatula was studied for establishment of the groundwork to investigate the regulatory mechanism of ROP in symbiotic interaction. 【Method】 The promoter sequence of MtROP5 was obtained using PCR, and the expression vectors containing MtROP5 were constructed. The method of Agrobacterium rhizogenes-mediated root transformation was used to investigate the function of MtROP5. 【Result】 The sequence of MtROP5 promoter that is at about 2.1 kb upstream of the translation origin point was obtained. The results showed that the MtROP5 promoter allowed GUS expression in every part of the root, GUS displayed more abundant expression level in vascular bundle and initials of lateral root than other parts of root. The transcriptional activity of MtROP5 promoter was induced to increase in the transgenic roots after infected by Sinorhizobium meliloti Rm1021. Compared with root hairs of the transgenic root of control, the length of transgenic root hairs of overexpression and constitutively active mutant of MtROP5 increased markedly by 74.6% and 54.8%, respectively, the length of transgenic root hair of RNAi interference of MtROP5 reduced by 47.6%, but the dominantly negative mutant of MtROP5 did not affect the development of root hairs. 【Conclusion】 MtROP5 in M. truncatula regulated the development of root hair, and probably involved in the signal transduction at the early stage of symbiotic interaction between host plant and Rhizobium.

Key words: Medicago truncatula')">Medicago truncatula, small G protein, ROP, symbiotic interaction, development of root hair