苹果炭疽叶枯病菌CgCMK1基因的克隆与功能分析

苹果炭疽叶枯病是由胶孢炭疽菌(Colletotrichum gloeosporioides)引起的苹果重要叶部病害,严重威胁苹果树的生长。CMK1-MAPK途径在植物病原真菌致病过程中具有重要的作用。本研究从苹果炭疽叶枯病菌中克隆了黄瓜炭疽病菌(C.lagenarium)CMK1的同源基因CgCMK1。CgCMK1基因ORF全长1 068 bp,编码355个氨基酸。CgCMK1敲除后不影响苹果炭疽叶枯病菌营养生长、色素沉积以及脂滴的转运。ΔCgCMK1突变体产孢能力显著下降、分生孢子萌发但不产生附着胞,外源添加cAMP不能诱导ΔCgCMK1突变体形成附着胞,在ΔCgCMK1突变体中,过表达cAMP信号途径依赖的蛋白激酶催化亚基基因CgCPK1也不能恢复突变体形成附着胞。CgCMK1基因参与氧化胁迫的应答反应,但不参与离子胁迫的应答反应。ΔCgCMK1突变体对苹果叶片完全丧失致病性,即使有伤接种也不能产生病斑。CgCMK1在苹果炭疽叶枯病菌分生孢子和附着胞中均有表达,定位于细胞质。上述结果表明,CgCMK1参与调控苹果炭疽叶枯病菌的分生孢子产量、附着胞的形成、氧化胁迫应答及致病性。

Cloning and functional analysis of CgCMK1 in Colletotrichum gloeosporioides

Glomerella leaf spot of apple (GLSA) caused mainly by Colletotrichum gloeosporioides has become a major apple leaf disease, which threatens apple growth. The CMK1-MAPK pathway plays an important role in the pathogenesis of plant pathogens. In this study, the homologous gene of C. lagenarium CMK1 in Colletotrichum gloeosporioides was cloned and designated as CgCMK1, which is 1 068 bp in ORF length, which encodes 355 amino acids. The CgCMK1 is not essential for vegetative growth, melanin pigmentation and lipid transport. The ΔCgCMK1 mutant that causes a significant decrease in conidiation is unable to form appressoria, exogenous cAMP couldn’t induce ΔCgCMK1 mutant form appressorium-like globular structures at the tips of germ tubes, protein kinase catalytic subunit CgCPK1 expressed continuously in ΔCgCMK1 mutant cannot restore the defect of appressorium formation. CgCMK1 is involved in the response to oxidative stress, but not in the response to ionic stress. The ΔCgCMK1 mutant is fully non-pathogenicity on apple leaves, even wounded leaves. Fluorescent signal showed that the fused protein CgCMK1-mCherry is distributed to the cytoplasm. These results demonstrated that CgCMK1 is involved in regulations of vegetative growth, conidium production, oxidative stress response and pathogenicity of C. gloeosporioides.