Type III secretion-dependent host defence elicitation and type III secretion-independent growth within leaves by Xanthomonas campestris pv. campestris.
Type III secretion-dependent host defence elicitation and type III secretion-independent growth within leaves by Xanthomonas campestris pv. campestris.
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DOI：
10.1111/j.1364-3703.2011.00707.x
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发表时间：
2011-10
影响因子：
4.9
通讯作者：
Wenxian Sun;Lijuan Liu;A. Bent
中科院分区：
文献类型：
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作者：
Wenxian Sun;Lijuan Liu;A. Bent
在许多植物-细菌相互作用中，III 型分泌系统 (T3SS) 的丧失会严重减少细菌的生长、症状的发生和宿主植物防御的抑制。在目前对野油菜黄单胞菌 pv 的研究中。油菜 (Xcc) 中，接种水囊后，Xcc 菌株 B305 在拟南芥中比菌株 B186 生长得更好，并且突变为 T3SS 缺失的 B305 菌株（ΔhrcC 和/或 ΔhrpE；还有 ΔhrcCΔflgBC）在拟南芥叶子中的生长与野生型 B305 类似。与Xcc菌株B186不同，野生型B305在分泌外源T3S效应子AvrBsT方面相对低效，但ΔhrcC和/或ΔhrpE减弱了Xcc B305引起的疾病症状，表明该菌株部分受损的T3SS仍然促进坏死叶症状。与在其他一些植物病原细菌中观察到的 T3SS 依赖性防御抑制相反，Xcc B186 和 B305 野生型菌株（对拟南芥有毒）与其各自的 T3SS 突变体相比，引起宿主 PR-1 和 PR-5 表达和胼胝质沉积更大的诱导。当与野生型 Xcc B186 共同接种增加 ΔhrcC Xcc 的生长时，可检测到 Xcc T3SS 效应器套件的防御抑制/毒力增强活性，但该活性并不能阻止上述防御诱导。使用 T3SS 突变体和拟南芥 fls2 突变体的实验表明，FLS2 在限制所检查的 Xcc 菌株中并未发挥显着作用。然而，丁香假单胞菌效应子 AvrPto 的异位过度表达促进了野生型和 ΔhrcC Xcc 的植物生长。总之，来自强毒 Xcc 菌株的 T3SS 成分或效应器套件会引发一些宿主防御反应，但会抑制其他防御并刺激更严重的疾病症状，除 FLS2 之外的 AvrPto 可破坏元件显然有助于 Xcc 的宿主限制，并且在一些强毒 Xcc 菌株中，T3SS 并不是植物内野生型细菌生长水平所绝对需要的。
In many plant-bacterial interactions, loss of the type III secretion system (T3SS) severely reduces bacterial growth, symptom causation and suppression of defences in host plants. In the present study of Xanthomonas campestris pv. campestris (Xcc), Xcc strain B305 grew better than strain B186 in Arabidopsis thaliana after hydathode inoculation, and B305 strains mutated to the loss of T3SS (ΔhrcC and/or ΔhrpE; also ΔhrcCΔflgBC) grew similarly to wild-type B305 in Arabidopsis leaves. Unlike Xcc strain B186, wild-type B305 was relatively inefficient in secreting the exogenous T3S effector AvrBsT, but ΔhrcC and/or ΔhrpE attenuated the disease symptoms caused by Xcc B305, showing that the partially compromised T3SS of this strain still promotes necrotic leaf symptoms. In contrast with the T3SS-dependent defence suppression that has been observed for some other plant pathogenic bacteria, the Xcc B186 and B305 wild-type strains (which are virulent on Arabidopsis) caused greater elicitation of host PR-1 and PR-5 expression and callose deposition in comparison with their respective T3SS mutants. A defence-suppressing/virulence-enhancing activity of the Xcc T3SS effector suite was detectable when co-inoculation with wild-type Xcc B186 increased the growth of ΔhrcC Xcc, but this activity did not prevent the above defence elicitation. Experiments using T3SS mutants and Arabidopsis fls2 mutants suggested that FLS2 does not play a prominent role in restriction of the examined Xcc strains. However, ectopic overexpression of the Pseudomonas syringae effector AvrPto promoted in planta growth of wild-type and ΔhrcC Xcc. In summary, the T3SS components or effector suite from virulent Xcc strains elicit some host defence responses, but suppress other defences and stimulate more severe disease symptoms, AvrPto-disruptable elements other than FLS2 apparently contribute to the host restriction of Xcc, and in some virulent Xcc strains the T3SS is not absolutely required for wild-type levels of bacterial growth within the plant.