1 Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Pillnitzer Platz 3a, 01326 Dresden-Pillnitz, Germany.
2 Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Ecological Chemistry, Plant Analysis and Stored Product Protection, Königin-Luise-Str. 19, 14195 Berlin, Germany.
Mol Plant Microbe Interact. 2018 Nov;31(11):1179-1191. doi: 10.1094/MPMI-12-17-0300-R. Epub 2018 Sep 11.
The AvrRpt2 effector protein of Erwinia amylovora is important for pathogen recognition in the fire blight-resistant crabapple Malus × robusta 5; however, little is known about its role in susceptible apples. To study its function in planta, we expressed a plant-optimized version of AvrRpt2 driven by a heat shock-inducible promoter in transgenic plants of the fire blight-susceptible cultivar Pinova. After induced expression of AvrRpt2, transgenic lines showed shoot necrosis and browning of older leaves, with symptoms similar to natural fire blight infections. Transgenic expression of this effector protein resulted in an increase in the expression of the salicylic acid (SA)-responsive PR-1 gene but, also, in the levels of SA and its derivatives, with diverse kinetics in leaves of different ages. In contrast, no increase of expression levels of VSP2 paralogs, used as marker genes for the activation of the jasmonic acid (JA)-dependent defense pathway, could be detected, which is in agreement with metabolic profiling of JA and its derivatives. Our work demonstrates that AvrRpt2 acts as a virulence factor and induces the formation of SA and SA-dependent systemic acquired resistance.
韧皮部坏死相关蛋白 2（AvrRpt2）是梨火疫病菌的效应蛋白，其在火疫病感病品种中的作用尚不清楚。为了研究其在植物体内的功能，我们在火疫病感病品种 Pinova 中，利用热休克诱导启动子表达了经植物优化的 AvrRpt2 蛋白。AvrRpt2 诱导表达后，转基因植株出现坏死和老叶黄化，与自然火疫病症状相似。该效应蛋白的转基因表达导致水杨酸（SA）应答 PR-1 基因的表达增加，但 SA 及其衍生物的水平也增加，不同年龄叶片中的动力学不同。相比之下，作为茉莉酸（JA）依赖防御途径激活的标记基因 VSP2 基因的表达水平没有增加，这与 JA 及其衍生物的代谢谱一致。我们的工作表明，AvrRpt2 作为一种毒力因子，诱导 SA 和 SA 依赖的系统获得性抗性的形成。
