State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
State Key Laboratory for Ecological Pest Control of Fujian and Taiwan Crops, College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Appl Microbiol Biotechnol. 2019 Jan;103(1):327-337. doi: 10.1007/s00253-018-9456-9. Epub 2018 Oct 24.
The biosynthesis of branched-chain amino acids (BCAAs) is conserved in fungi and plants, but not in animals. The Leu1 gene encodes isopropylmalate isomerase that catalyzes the conversion of α-isopropylmalate into β-isopropylmalate in the second step of leucine biosynthesis in yeast. Here, we identified and characterized the functions of MoLeu1, an ortholog of yeast Leu1 in the rice blast fungus Magnaporthe oryzae. The transcriptional level of MoLEU1 was increased during conidiation and in infectious stages. Cellular localization analysis indicated that MoLeu1 localizes to the cytoplasm at all stages of fungal development. Targeted gene deletion of MoLEU1 led to leucine auxotrophy, and phenotypic analysis of the generated ∆Moleu1 strain revealed that MoLeu1-mediated leucine biosynthesis was required for vegetative growth, asexual development, and pathogenesis of M. oryzae. We further observed that invasive hyphae produced by the ∆Moleu1 strain were mainly limited to the primary infected host cells. The application of exogenous leucine fully restored vegetative growth and partially restored conidiation as well as pathogenicity defects in the ∆Moleu1 strain. In summary, our results suggested that MoLeu1-mediated leucine biosynthesis crucially promotes vegetative growth, conidiogenesis, and pathogenicity of M. oryzae. This study helps unveil the regulatory mechanisms that are essential for infection-related morphogenesis and pathogenicity of the rice blast fungus.
分支链氨基酸（BCAAs）的生物合成在真菌和植物中是保守的，但在动物中却不是。Leu1 基因编码异亮氨酸生物合成途径中的第二个酶，即异丙基苹果酸异构酶，它催化α-异戊烯基苹果酸转化为β-异戊烯基苹果酸。在这里，我们鉴定并表征了水稻纹枯病菌中酵母 Leu1 的直系同源物 MoLeu1 的功能。MoLEU1 的转录水平在分生孢子形成和感染阶段增加。细胞定位分析表明，MoLeu1 在真菌发育的所有阶段都定位于细胞质中。MoLEU1 基因的靶向敲除导致亮氨酸营养缺陷，对生成的 ∆Moleu1 菌株的表型分析表明，MoLeu1 介导的亮氨酸生物合成对于营养生长、无性发育和稻瘟病菌的致病性是必需的。我们进一步观察到，∆Moleu1 菌株产生的侵入性菌丝主要局限于初级感染的宿主细胞。外源性亮氨酸的应用完全恢复了∆Moleu1 菌株的营养生长，并部分恢复了其分生孢子形成和致病性缺陷。总之，我们的结果表明，MoLeu1 介导的亮氨酸生物合成对稻瘟病菌的营养生长、分生孢子形成和致病性至关重要。本研究有助于揭示与感染相关的形态发生和稻瘟病菌致病性所必需的调控机制。
