College of Forestry, Beijing Forestry University, Beijing, China.
Museum of Beijing Forestry University, Beijing Forestry University, Beijing, China.
Fungal Genet Biol. 2019 Jul;128:1-13. doi: 10.1016/j.fgb.2019.03.005. Epub 2019 Mar 13.
Cytospora chrysosperma, the causal agent of canker disease in a wide range of woody plants, results in significant annual economic and ecological losses. Mitogen-activated protein kinase (MAPK) cascades are highly conserved signal transduction pathways that play a crucial role in mediating cellular responses to environmental and host signals in plant pathogenic fungi. In this study, we identified an ortholog of the Fus3/Kss1-related MAPK gene, CcPmk1, and characterized its functions in C. chrysosperma. The expression of CcPmk1 was highly induced by inoculation on poplar twigs, and targeted deletion of CcPmk1 resulted in the loss of pathogenicity, indicating that CcPmk1 is an important regulator of virulence. In addition, CcPmk1 deletion mutants (ΔCcPmk1) displayed reduced growth and conidiation, decreased fungal biomass production and hyperbranching. Furthermore, our results indicated that CcPmk1 deletion mutants exhibited hypersensitivity to cell wall inhibitors and cell wall-degrading enzymes. Correspondingly, the transcription of cell wall biosynthesis-related genes in the ΔCcPmk1 strain was downregulated compared to that in the wild-type strain. Moreover, we found that CcPmk1 could positively regulate the expression of several candidate effector encoding genes which were highly induced in planta. Hence, we hypothesized that CcPmk1 regulates the expression of a series of effectors to promote virulence. Overall, we concluded that the functions of CcPmk1 extend to fungal development, cell wall integrity and pathogenicity in C. chrysosperma.
壳二孢菌（Cytospora chrysosperma）是广泛木本植物溃疡病的致病因子，导致每年重大的经济和生态损失。丝裂原活化蛋白激酶（MAPK）级联反应是高度保守的信号转导途径，在植物病原真菌中对介导细胞对环境和宿主信号的反应起着至关重要的作用。在本研究中，我们鉴定了一个与 Fus3/Kss1 相关的 MAPK 基因的同源物 CcPmk1，并对其在壳二孢菌中的功能进行了表征。CcPmk1 的表达在杨树嫩枝接种后高度诱导，靶向敲除 CcPmk1 导致致病性丧失，表明 CcPmk1 是毒力的重要调节因子。此外，CcPmk1 缺失突变体（ΔCcPmk1）表现出生长和产孢减少、真菌生物量产生减少和过度分枝。此外，我们的结果表明，CcPmk1 缺失突变体对细胞壁抑制剂和细胞壁降解酶表现出超敏反应。相应地，ΔCcPmk1 菌株中细胞壁生物合成相关基因的转录水平较野生型菌株下调。此外，我们发现 CcPmk1 可以正向调控一些候选效应因子编码基因的表达，这些基因在植物体内高度诱导。因此，我们假设 CcPmk1 调节一系列效应因子的表达以促进毒力。总体而言，我们得出结论，CcPmk1 的功能扩展到壳二孢菌的真菌发育、细胞壁完整性和致病性。
