Liu Yuwei, Gong Xiaodong, Li Moxiao, Si Helong, Zhou Qihui, Liu Xingchen, Fan Yu, Zhang Xiaoyu, Han Jianmin, Gu Shouqin, Dong Jingao
State Key Laboratory of North China Crop Improvement and Regulation, Baoding, China.
College of Life Sciences, Hebei Agricultural University, Baoding, China.
Front Microbiol. 2021 Jul 23;12:706349. doi: 10.3389/fmicb.2021.706349. eCollection 2021.
Osmotic stress is a severe condition frequently encountered by microorganisms; however, there is limited knowledge on the influence of hyperosmotic stress on the growth, development and pathogenicity of phytopathogenic fungi. Here, three osmotic conditions (0.4 M NaCl, 0.4 M KCl, and 0.6 M sorbitol supplemented in potato dextrose agar medium) were used to identify the effect of osmotic stress on the growth, development and pathogenicity of which is a plant pathogenic fungus and causes northern corn leaf blight disease in maize, sorghum, and related grasses. In osmotic stress, the growth rate of mycelium was decreased, and the number of vesicular structures and flocculent secretion outside the hypha cell wall were significantly increased. The qRT-PCR results showed that the osmotic stress quickly activated the HOG-MAPK pathway, up-regulated the expression of the downstream genes, and these genes were most highly expressed within 30 min of exposure to osmotic stress. Furthermore, the germination rate and the yield of conidia were significantly higher under osmotic stress than in the control. A pathogenicity analysis confirmed that pathogenicity of the conidia which were cultured under osmotic stress was significantly enhanced. By analyzing the knock-out mutants of an osmotic stress responsed gene , an aquaglyceroporin downstream of the HOG-MAPK pathway, we found that was involved in the formation of appressorium and penetration peg, which affected the penetration ability of . In summary, our work explained the correlation between osmotic stress and growth, development, and pathogenicity in .
渗透胁迫是微生物经常遇到的一种严峻状况；然而，关于高渗胁迫对植物病原真菌的生长、发育和致病性的影响，人们了解有限。在此，我们使用了三种渗透条件（在马铃薯葡萄糖琼脂培养基中添加0.4 M NaCl、0.4 M KCl和0.6 M山梨醇）来确定渗透胁迫对一种植物病原真菌的生长、发育和致病性的影响，这种真菌会在玉米、高粱及相关禾本科植物中引发玉米大斑病。在渗透胁迫下，菌丝体的生长速率下降，菌丝细胞壁外的泡状结构和絮状分泌物数量显著增加。定量逆转录聚合酶链反应（qRT-PCR）结果表明，渗透胁迫迅速激活了高渗甘油促分裂原活化蛋白激酶（HOG-MAPK）信号通路，上调了下游基因的表达，并且这些基因在暴露于渗透胁迫30分钟内表达量最高。此外，渗透胁迫下分生孢子的萌发率和产量显著高于对照。致病性分析证实，在渗透胁迫下培养的分生孢子的致病性显著增强。通过分析一个渗透胁迫响应基因（HOG-MAPK信号通路下游的一种水甘油通道蛋白）的敲除突变体，我们发现该基因参与附着胞和侵入钉的形成，从而影响了该真菌的穿透能力。总之，我们的研究解释了渗透胁迫与该真菌的生长、发育和致病性之间的相关性。
