Population behavior analysis of dspE and pelD regulation in Erwinia chrysanthemi 3937

• Published in: Molecular plant-microbe interactions Vol. 19; no. 4; pp. 451 - 457
• Main Authors: Peng, Q, Yang, S, Charkowski, A.O, Yap, M.N, Steeber, D.A, Keen, N.T, Yang, C.H
• Format: Journal Article
• Language: English
• Published: St Paul, MN APS Press 01.04.2006; The American Phytopathological Society
• Subjects: Bacterial plant pathogens; bacterial proteins; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Biological and medical sciences; Brassica - microbiology; Erwinia chrysanthemi; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Bacterial; pectin lyase; pectinase; Pectobacterium chrysanthemi; Pectobacterium chrysanthemi - genetics; Pectobacterium chrysanthemi - physiology; Phytopathology. Animal pests. Plant and forest protection; plant pathogenic bacteria; Plant Tubers - microbiology; Polysaccharide-Lyases - genetics; Polysaccharide-Lyases - metabolism; Promoter Regions, Genetic; Solanum tuberosum; Solanum tuberosum - microbiology; Type III secretion system; Culture medium; Plant pathogen; Enzyme; Solanum tuberosum; Secretion; Virulence; Gene expression; Type III secretion system; Reporter gene; Pectinolytic enzyme; pectinase; Dicotyledones; Angiospermae; Erwinia chrysanthemi; Green fluorescent protein; Deletion; Host range; Bacteria; Spermatophyta; Tuber plant; Solanaceae; Mutation; Enterobacteriaceae
• ISSN: 0894-0282; 1943-7706
• DOI: 10.1094/MPMI-19-0451

Erwinia chrysanthemi 3937 (Ech3937) is a phytopathogenic bacterium with a wide host range. The pectinolytic enzymes secreted by the bacterium and the type III secretion system (T3SS) are essential for full virulence. We used the green fluorescent protein gene as a reporter to investigate the expression of dspE (a putative T3SS effector) and pelD (a major pectin-degrading enzyme) in populations of Ech3937 under different conditions. Gene expression was analyzed by measuring the fluorescence intensity of individual cells with a fluorescence-activated cell sorter. Ech3937 dspE was induced in minimal medium (MM) with only a portion of Ech3937 cells (43.03%) expressing dspE after 12 h of culture. The nutrient-rich King's medium B did not fully eliminate the expression of dspE; a small percentage of Ech3937 cells (5.55%) was able to express dspE after 12 h of culture in this medium. In all, 68.95% of Ech3937 cells expressed pelD after 12 h of culture in MM supplemented with polygalacturonic acid (PGA). However, 96.34% of Echl31 cells (an hrpL deletion mutant of Ech3937) expressed pelD after 12 h of culture in MM supplemented with PGA. In potato tubers, 6.32% of the bacterial cells expressed dspE 2 h after inoculation, whereas only 0.25% of the cells expressed pelD. However, after 24 h, the percentage of cells expressing pelD (68.48%) was approximately 3.5 times that of cells expressing dspE (19.39%). In contrast to potato tubers, similar proportion of Ech3937 cells expressing dspE (39.34%) and pelD (40.30%) were observed in Chinese cabbage 24 h after inoculation. From promoter activity and real-time quantitative results, the expression of pelD in Ech3937 was demonstrated to be downregulated by HrpL in MM supplemented with PGA.