关键词: 施氏假单胞菌A1501；生物固氮；rsmA；rsmZ；转录调控

Abstract:

RsmA is a highly conservative global regulator in Pseudomonas, which could affect mRNA stability or control the translation of the target gene, and then to affect protine expression by combining mRNA of the target gene. In nitrogen-fixing Pseudomonas stutzeri A1501, there were one rsmA homologus gene and one non\|coding small RNA gene rsmZ that might regulate RsmA activity. The evolution of RsmA and RsmZ in A1501 and conducted additional studies on their expression indicated that RsmA of A1501 shared 98% genetic similarity with RsmA of Pseudomonas aeruginosa PAO1 and RsmZ contained 4 RsmA binding sites. The real\|time PCR results showed that the rsmA transcription level was high in early growing period and drops down in the exponential growing and stable phases. The expression of rsmZ did not change significantly during the whole growing period. Under carbon starvation conditions,  rsmA and rsmZ genes showed a significantly reduced level of transcription. The mutation of rpoS did not affect rsmA expression; however, rsmZ transcription was enhanced by 30\|fold, indicating that rsmZ was negatively regulated by rpoS. Further study indicated that there were no changes in the expression of rsmA and rsmZ in gacA mutant. Based on the above experiments, the regulatory model of rsmA and rsmZ in A1501 was different from other Pseudomonas, such as Pseudomonas fluorescens CHAO and Pseudomonas aeruginosa PAO1. This paper has laid a theoretical foundation for further studying rsmA function and its regulatory mechanism under spesific condition.

Key words: Pseudomonas stutzeri A1501, nitrogen fixation, rsmA, rsmZ, transcriptional regulation