Hugouvieux-Cotte-Pattat N, Dominguez H, Robert-Baudouy J
Laboratoire de Génétique Moléculaire des Microorganismes, URA-CNRS, Institut National des Sciences Appliquées batiment 406, Villeurbanne, France.
J Bacteriol. 1992 Dec;174(23):7807-18. doi: 10.1128/jb.174.23.7807-7818.1992.
To depolymerize plant pectin, the phytopathogenic enterobacterium Erwinia chrysanthemi produces a series of enzymes which include a pectin-methyl-esterase encoded by the pem gene and five isoenzymes of pectate lyases encoded by the five genes pelA, pelB, pelC, pelD, and pelE. We have constructed transcriptional fusions between the pectinase gene promoters and the uidA gene, encoding beta-glucuronidase, to study the regulation of these E. chrysanthemi pectinase genes individually. The transcription of the pectinase genes is dependent on many environmental conditions. All the fusions were induced by pectic catabolic products and responded, to different degrees, to growth phase, catabolite repression, temperature, and nitrogen starvation. Transcription of pelA, pelD, and pelE was also increased in anaerobic growth conditions. High osmolarity of the culture medium increased expression of pelE but decreased that of pelD; the other pectinase genes were not affected. The level of expression of each gene was different. Transcription of pelA was very low under all growth conditions. The expression of the pelB, pelC, and pem genes was intermediate. The pelE gene had a high basal level of expression. Expression of pelD was generally the most affected by changes in culture conditions and showed a low basal level but very high induced levels. These differences in the expression of the pectinase genes of E. chrysanthemi 3937 presumably reflect their role during infection of plants, because the degradation of pectic polymers of the plant cell walls is the main determinant of tissue maceration caused by soft rot erwiniae.
为了解聚植物果胶，植物致病性肠道细菌菊欧文氏菌产生一系列酶，其中包括由pem基因编码的果胶甲基酯酶以及由pelA、pelB、pelC、pelD和pelE这五个基因编码的五种果胶酸裂解酶同工酶。我们构建了果胶酶基因启动子与编码β-葡萄糖醛酸酶的uidA基因之间的转录融合体，以单独研究这些菊欧文氏菌果胶酶基因的调控。果胶酶基因的转录取决于许多环境条件。所有融合体均由果胶分解代谢产物诱导，并在不同程度上对生长阶段、分解代谢物阻遏、温度和氮饥饿作出反应。在厌氧生长条件下，pelA、pelD和pelE的转录也会增加。培养基的高渗透压会增加pelE的表达，但会降低pelD的表达；其他果胶酶基因不受影响。每个基因的表达水平各不相同。在所有生长条件下，pelA的转录都非常低。pelB、pelC和pem基因的表达处于中等水平。pelE基因具有较高的基础表达水平。pelD的表达通常受培养条件变化的影响最大，基础表达水平较低，但诱导表达水平非常高。菊欧文氏菌3937果胶酶基因表达上的这些差异可能反映了它们在植物感染过程中的作用，因为植物细胞壁果胶聚合物的降解是软腐欧文氏菌引起组织浸解的主要决定因素。
