Population behavior analysis of dspE and pelD regulation in Erwinia chrysanthemi 3937.
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.
Peng
Quan
Q
Department of Biological Sciences, University of Wisconsin, Milwaukee 53211, USA.
Yang
Shihui
S
Charkowski
Amy O
AO
Yap
Mee-Ngan
MN
Steeber
Douglas A
DA
Keen
Noel T
NT
Yang
Ching-Hong
CH
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001937:Brassica / Q000382:microbiology; D016974:Dickeya chrysanthemi / Q000235:genetics* / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial; D035281:Plant Tubers / Q000382:microbiology; D011133:Polysaccharide-Lyases / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011198:Solanum tuberosum / Q000382:microbiology
D001426:Bacterial Proteins; D011133:Polysaccharide-Lyases; C023911:pectate lyase