Hugouvieux-Cotte-Pattat N, Condemine G, Nasser W, Reverchon S
Laboratoire de Génétique Moléculaire des Microorganismes, UMR-CNRS 5577, Villeurbanne, France.
Annu Rev Microbiol. 1996;50:213-57. doi: 10.1146/annurev.micro.50.1.213.
Erwinia chrysanthemi is an enterobacterium that causes various plant diseases. Its pathogenicity results from the secretion of pectinolytic enzymes responsible for the disorganization of the plant cell wall. The E. chrysanthemi strain 3937 produces two pectin methylesterases, at least seven pectate lyases, a polygalacturonase, and a pectin lyase. The extracellular degradation of the pectin leads to the formation of oligogalacturonides that are catabolized through an intracellular pathway. The pectinase genes are expressed from independent cistrons, and their transcription is favored by environmental conditions such as presence of pectin and plant extracts, stationary growth phase, low temperature, oxygen or iron limitation, and so on. Moreover, transcription of the pectin lyase gene responds to DNA-damaging agents. The differential expressions of individual pectinase genes presumably reflect their role during plant infection. The regulation of pel genes requires several regulatory systems, including the KdgR repressor, which mediates the induction of all the pectinolysis genes in the presence of pectin catabolites. KdgR also controls the genes necessary for pectinase secretion and other pectin-inducible genes not yet characterized. PecS, a cytoplasmic protein homologous to other transcriptional regulators, can bind in vitro to the regulatory regions of pectinase and cellulase genes. The PecT protein, a member of the LysR family of transcriptional regulators, represses the expression of some pectinase genes and also affects other metabolic pathways of the bacteria. Other proteins involved in global regulations, such as CRP or HNS, can bind to the regulatory regions of the pectinase genes and affect their transcription.
菊欧文氏菌是一种能引发多种植物病害的肠道细菌。其致病性源于分泌果胶分解酶，这些酶会导致植物细胞壁解体。菊欧文氏菌3937菌株产生两种果胶甲酯酶、至少七种果胶酸裂解酶、一种多聚半乳糖醛酸酶和一种果胶裂解酶。果胶的胞外降解会导致寡聚半乳糖醛酸的形成，这些寡聚半乳糖醛酸通过细胞内途径被分解代谢。果胶酶基因由独立的顺反子表达，其转录受到果胶和植物提取物的存在、稳定生长期、低温、氧气或铁限制等环境条件的促进。此外，果胶裂解酶基因的转录对DNA损伤剂有反应。各个果胶酶基因的差异表达大概反映了它们在植物感染过程中的作用。pel基因的调控需要多种调控系统，包括KdgR阻遏物，它在果胶分解代谢物存在时介导所有果胶分解基因的诱导。KdgR还控制果胶酶分泌所需的基因以及其他尚未鉴定的果胶诱导基因。PecS是一种与其他转录调节因子同源的胞质蛋白，在体外可与果胶酶和纤维素酶基因的调控区域结合。PecT蛋白是转录调节因子LysR家族的成员，它抑制一些果胶酶基因的表达，还影响细菌的其他代谢途径。其他参与全局调控的蛋白质，如CRP或HNS，可与果胶酶基因的调控区域结合并影响其转录。
