Institute of Tropical Agriculture and Forestry, Hainan University, Haikou, Hainan Province, China.
Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests (Hainan University), Ministry of Education, Haikou, 570228, Hainan Province, China.
Sci Rep. 2019 Jan 30;9(1):990. doi: 10.1038/s41598-018-37886-9.
Harpin proteins are produced by plant-pathogenic Gram-negative bacteria and regulate bacterial pathogenicity by inducing plant growth and defence responses in non-hosts. HpaG-Xcm, a novel harpin protein, was identified from Xanthomonas citri pv. mangiferaeindicae, which causes bacterial black spot of mango. Here, we describe the predicted structure and functions of HpaG-Xcm and investigate the mechanism of heat resistance. The HpaG-Xcm amino acid sequence contains seven motifs and two α-helices, in the N- and C-terminals, respectively. The N-terminal α-helical region contains two heptads, which form the coiled-coil (CC) structure. The CC region, which is on the surface of HpaG-Xcm, forms oligomeric aggregates by forming hydrophobic interactions between hydrophobic amino acids. Like other harpins, HpaG-Xcm was heat stable, promoted root growth and induced a hypersensitive response (HR) and systemic acquired resistance in non-host plants. Subjecting HpaG-Xcm to high temperatures altered the gene expression induced by HpaG-Xcm in tobacco leaves, probably due to changes in the spatial structure of HpaG-Xcm. Phenotypic tests revealed that the high-temperature treatments reduced the HR and disease resistance induced by HpaG-Xcm but had little effect on growth promotion. These findings indicate that the stability of interactions between CC and plants may be associated with thermal stability of HpaG-Xcm.
Harpin 蛋白由植物病原革兰氏阴性细菌产生，通过在非宿主中诱导植物生长和防御反应来调节细菌的致病性。HpaG-Xcm 是一种从引起芒果细菌性黑斑病的柑橘黄单胞菌 pv. mangiferaeindicae 中鉴定出的新型 harpin 蛋白。在这里，我们描述了 HpaG-Xcm 的预测结构和功能，并研究了其耐热性的机制。HpaG-Xcm 的氨基酸序列包含七个基序和两个α-螺旋，分别位于 N-和 C-末端。N-末端α-螺旋区域包含两个七肽重复序列，它们形成卷曲螺旋 (CC) 结构。CC 区域位于 HpaG-Xcm 的表面，通过形成疏水性氨基酸之间的疏水相互作用形成寡聚体聚集。与其他 harpins 一样，HpaG-Xcm 具有热稳定性，可促进根生长，并在非宿主植物中诱导过敏反应 (HR) 和系统获得性抗性。将 HpaG-Xcm 置于高温下会改变 HpaG-Xcm 在烟草叶片中诱导的基因表达，这可能是由于 HpaG-Xcm 空间结构的变化所致。表型测试表明，高温处理降低了 HpaG-Xcm 诱导的 HR 和抗病性，但对促进生长的影响很小。这些发现表明，CC 与植物之间相互作用的稳定性可能与 HpaG-Xcm 的热稳定性有关。
