Department of Plant Pathology & Ecology, The Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, CT 06511, United States.
Department of Plant Pathology & Environmental Microbiology, The Pennsylvania State University, University Park, PA 16802, United States.
J Appl Microbiol. 2024 Aug 5;135(8). doi: 10.1093/jambio/lxae185.
The Gram-negative bacterium Erwinia amylovora (Ea) is the causal agent of fire blight, a devastating disease of apples and pears. In the fire blight disease cycle, Ea grows in different plant tissues, each presenting a distinct nutrient environment. Here, we investigate the ability of aspartate and tyrosine double auxotroph Ea lines to proliferate on apple flower stigma surfaces representing the epiphytic growth stage of Ea and in developing fruitlets representing one endophytic growth stage of Ea.
Heterologous complementation studies in an Escherichia coli aspartate and tyrosine auxotroph verify that Ea aspartate aminotransferase (AspC) and tyrosine aminotransferase (TyrB) act as aspartate and tyrosine amino transferases. Growth analysis reveals that Ea aspC tyrB mutants multiply to near-wild-type levels on apple flower stigmas and immature fruitlets.
Ea AspC and TyrB are reciprocally complementing for aspartate and tyrosine synthesis in Ec and in Ea. Ea aspC and tyrB mutants obtain sufficient aspartate and tyrosine to support multiplication on stigma surfaces and virulence in immature fruitlets.
革兰氏阴性细菌果胶杆菌（Ea）是火疫病的病原体，火疫病是苹果和梨的毁灭性疾病。在火疫病的发病周期中，Ea 在不同的植物组织中生长，每个组织都呈现出不同的营养环境。在这里，我们研究天冬氨酸和酪氨酸双重营养缺陷型 Ea 系在代表 Ea 附生生长阶段的苹果花朵柱头上和代表 Ea 一种内生生长阶段的发育幼果上增殖的能力。
在大肠杆菌天冬氨酸和酪氨酸营养缺陷型的异源互补研究中，验证了 Ea 天冬氨酸氨基转移酶（AspC）和酪氨酸氨基转移酶（TyrB）作为天冬氨酸和酪氨酸氨基转移酶的作用。生长分析表明，Ea aspC tyrB 突变体在苹果花朵柱头上和未成熟的幼果上的增殖接近野生型水平。
Ea AspC 和 TyrB 在 Ec 和 Ea 中相互补充合成天冬氨酸和酪氨酸。Ea aspC 和 tyrB 突变体获得足够的天冬氨酸和酪氨酸，以支持在柱头表面的增殖和在未成熟幼果中的毒力。
