The ability of rhizobia to symbiotically fix nitrogen from the atmosphere when forming nodules on their host plant roots requires signal transduction pathways LuxR/LuxI family proteins are a unique quorum-sensing system,found in many bacteria,LuxR is a regulatory prote in which regulates LuxI-type proteins in synthesizing autoinducer (AI) In this study,sequence analysis was conducted finding a LuxI type synthase gene,mrtI,and a regulatory gene mrtR present in Mtian shanense,which are homologic to the LuxR/LuxI type of protein.Using gene knock-out,mrtR was found regulating the expression of mrtI.Furthermore,and using lacZ transcriptional fusion,AHL molecule demonstrating a key role in mrtR expression,which proves that mrtR is autoregu lated.The root hair adherence experiment showed that mtR affected plant bacteria interaction.These data show that it is necessary to have MrtR bonded with AHLs for mrtI expression and the gene plays a key role in regulating the quorum sensing system of M.tianshanense.