Function Analysis Of RHO GTPase PsRAC1in Phytophthora Sojae

Phytophthora sojae is the casual agent of damping off of the seedlings and root rot disease of soybean, which is an economically important crop around the world. It is one of the most notorious pathogens which caused tremendous economic loss in soybean production annually. P. sojae switch the life stages by sensing hormone, temperature, humidity and other environmental conditions.During infection of their hosts, P. sojae secreted a variety of extracellular proteins to promote the pathogenicity. Therefore, to study the mechanism that P. sojae sense the environmental factors and the signal transduction pathway, and the process that P sojae secretie extracellular proteins will provide theoretical bases for disease control. Methods for reverse genetics involving gene disruption are not currently feasible in oomycetes due to low rates of homologous recombination during transformation and diploidy. The molecular mechanisms underlying development and infection are largely unknown. As the increasing mount of the genome sequence and transcription profile data for P. sojae available, a feasible and efficient genetics protocols is critical for studying the biology, pathogenicity, and evolution of these organisms.Bioinformatics prediction and transcription analysis of Rho GTPase family in phytophthora sojae.The Rho GTPase family proteins are major members of the Ras super family small GTPases, conserved in the eukaryotic cells.The Rho GTPase family consists of subfamily members of Rho, RacandCdc42, which act as molecular switches in several signal transduction pathways, such as in the regulation of cell polarity, cell movement, cell shape, and cell-cell and cell-matrix interaction. In this study, we got one Rho GTPase protein named PsRacl in the genome of p.sojae according to the method of bioinformatics. In P. sojae, the transcription profile of PsRacl was also performed by qRT-PCR. These results provide a new study way for analysis function gene, which is crucial to disease control and drug development.PsRacl is involved in growing development and pathogenicity in Phytophthora sojae. zoospores have the characteristic of chemotaxis, which can swim chemotactically toward compounds released by roots of their host plants, and then encyst on the root surface from where the hyphae penetrate the root directly from the cyst. Expression of PsRacl was silenced by the transformation system of Phytophthora sojae. The growth rate and the distribution of esicle in the top hypha of silenced mutants were reduced, cyst germination and the formation of lateral branches were badly affected, resulting in the inability of infecting soybean in PsRacl-silenced mutants. Silenced mutants and wild type exhibited no differences in the structure of the cell wall, eliminating AOS and eliciting callose.These results suggested that has very important effect on zoospore pathogenicity to soybean and cyst germination.