The key Sinorhizobium meliloti succinoglycan biosynthesis gene exoY is expressed from two promoters

摘要

Bacterial exopolysaccharide, succinoglycan, plays an important role in eliciting infection thread formation, which is a key step in the establishment of Sinorhizobium meliloti-alfalfa (Medicago sativa) nitrogen fixing symbiosis. To understand the regulatory mechanisms that control production of succinoglycan, the expression of the key succinoglycan biosynthesis gene, exoY, was analyzed by constructing a set of nested deletions of the exo Y promoter region. Two exo Y promoters were identified based on the promoter activities and confirmed by direct detection of the transcripts. The expression from both promoters was induced in the exoR95 and exoS96 mutant backgrounds suggesting that both promoters are regulated by the ExoR protein and the ExoS/ChvI two-component signal transduction system. The identification of the exoY promoters provides additional avenue for further analysis of the role of succinoglycan in S. meliloti-alfalfa symbiosis. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved. [References: 28]