INACTIVATION OF MULTIPLE VIRULENCE GENES REDUCES THE ABILITY OF PSEUDOMONAS-SOLANACEARUM TO CAUSE WILT SYMPTOMS
INACTIVATION OF MULTIPLE VIRULENCE GENES REDUCES THE ABILITY OF PSEUDOMONAS-SOLANACEARUM TO CAUSE WILT SYMPTOMS
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DOI：
10.1094/mpmi-3-293
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发表时间：
1990-09-01
影响因子：
3.5
通讯作者：
SCHELL, MA
中科院分区：
文献类型：
--
作者：
DENNY, TP;CARNEY, BF;SCHELL, MA
对青枯假单胞菌（Pseudomonassolanacearum）的研究表明，内切葡聚糖酶（egl编码）、内切多聚半乳糖醛酸酶（pglA编码）和胞外多糖（eps基因编码）是番茄枯萎病的致病因子。我们现在已经构建了青枯菌的egl pglA和egl eps双突变体，并将它们与单突变体在培养物中胞外酶的产生以及通过茎和根接种程序的毒力进行比较。egl和egl eps突变体不产生内切葡聚糖酶活性，但出乎意料地过度产生多聚半乳糖醛酸酶（PG）活性30%至140%。在野生型或egl 9：：Tn 5背景中pglA的失活使总PG活性降低约25至50%。粘度数据表明，pglA突变体的内切-PG活性不足，但保留外切-PG活性。当106个细菌注入番茄植株的茎部或当106个细菌倒在土壤中时，pglA和egl pglA突变体的毒力不受影响;当茎部接种突变体的106个细菌时，植株比接种亲本菌株的植株萎蔫慢1至2天。相比之下，egl的失活一致地降低了青枯菌使番茄植物枯萎的能力，而与菌株、测定类型或测试的接种物浓度无关。egl eps突变体在三分之二的茎接种实验中没有使植物枯萎，并且当加入土壤中时似乎也没有感染植物，它是确定的突变体中毒性最小的。根接种试验也被用来显示萎蔫症状的外观和减少水分利用的植物之间的密切关系，加强假设萎蔫是血管功能障碍的结果。
Previous research on Pseudomonas solanacearum had shown that endoglucanase (encoded by egl), endopolygalacturonase (encoded by pglA), and extracellular polysaccharide (encoded by multiple eps genes) are each virulence factors involved in wilt disease of tomato. We have now constructed egl pglA and egl eps double mutants of P. solanacearum and compared them to the single mutants for production of extracellular enzymes in culture and for virulence by both stem and root inoculation procedures. The egl and egl eps mutants produced no endoglucanase activity, but unexpectedly overproduced polygalacturonase (PG) activity by 30 to 140%. Inactivation of pglA in either a wild-type or egl9::Tn5 background reduced total PG activity approximately 25 to 50%. Viscometry data indicated that the pglA mutants were deficient in endo-PG activity, but retained exo-PG activity. Virulence of the pglA and egl pglA mutants was not affected when 106 bacteria were injected into stems of tomato plants or when 106 bacteria were poured onto the soil; when stems were inoculated with 106 bacteria of the mutants, the plants wilted 1 to 2 days slower than those inoculated with the parent strains. In contrast, inactivation of egl consistently reduced the ability of P. solanacearum to wilt tomato plants regardless of the strain, the type of assay, or the inoculum concentration tested. The egl eps mutant, which did not wilt plants in two-thirds of the stem inoculation experiments and appeared not to infect plants when added to the soil, was the least virulent of the defined mutants. The root inoculation assay was also used to show the close relationship between the appearance of wilt symptoms and reduced water use by the plant, strengthening the hypothesis that wilt is the result of vascular dysfunction.