Huang Shuaishuai, He Zhangjiang, Zhang Shiwei, Keyhani Nemat O, Song Yulin, Yang Zhi, Jiang Yahui, Zhang Wenli, Pei Yan, Zhang Yongjun
College of Plant Protection, Biotechnology Research Center, Southwest University, Chongqing 400715, People's Republic of China.
Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA.
Fungal Genet Biol. 2015 Oct;83:78-91. doi: 10.1016/j.fgb.2015.08.009. Epub 2015 Aug 28.
The entomopathogenic fungus, Beauveria bassiana, is of environmental and economic importance as an insect pathogen, currently used for the biological control of a number of pests. Cell wall integrity and conidiation are critical parameters for the ability of the fungus to infect insects and for production of the infectious propagules. The contribution of calcineurin and the Slt2 MAP kinase to cell wall integrity and development in B. bassiana was investigated. Gene knockouts of either the calcineurin CNA1 subunit or the Slt2 MAP kinase resulted in decreased tolerance to calcofluor white and high temperature. In contrast, the Δcna1 strain was more tolerant to Congo red but more sensitive to osmotic stress (NaCl, sorbitol) than the wild type, whereas the Δslt2 strain had the opposite phenotype. Changes in cell wall structure and composition were seen in the Δslt2 and Δcna1 strains during growth under cell wall stress as compared to the wild type. Both Δslt2 and Δcna1 strains showed significant alterations in growth, conidiation, and viability. Elevation of intracellular ROS levels, and decreased conidial hydrophobicity and adhesion to hydrophobic surfaces, were also seen for both mutants, as well as decreased virulence. Under cell wall stress conditions, inactivation of Slt2 significantly repressed CN-mediated phosphatase activity suggesting some level of cross talk between the two pathways. Comparative transcriptome profiling of the Δslt2 and Δcna1 strains revealed alterations in the expression of distinct gene sets, with overlap in transcripts involved in cell wall integrity, stress response, conidiation and virulence. These data illustrate convergent and divergent phenotypes and targets of the calcineurin and Slt2 pathways in B. bassiana.
昆虫病原真菌球孢白僵菌作为一种昆虫病原体，在环境和经济方面具有重要意义，目前被用于多种害虫的生物防治。细胞壁完整性和分生孢子形成是该真菌感染昆虫以及产生感染性繁殖体能力的关键参数。研究了钙调神经磷酸酶和Slt2丝裂原活化蛋白激酶对球孢白僵菌细胞壁完整性和发育的作用。钙调神经磷酸酶CNA1亚基或Slt2丝裂原活化蛋白激酶的基因敲除导致对荧光增白剂和高温的耐受性降低。相比之下，Δcna1菌株对刚果红更具耐受性，但比野生型对渗透胁迫（NaCl、山梨醇）更敏感，而Δslt2菌株具有相反的表型。与野生型相比，在细胞壁胁迫下生长的Δslt2和Δcna1菌株的细胞壁结构和组成发生了变化。Δslt2和Δcna1菌株在生长、分生孢子形成和活力方面均表现出显著改变。两个突变体还出现细胞内活性氧水平升高、分生孢子疏水性降低以及对疏水表面的粘附性降低，同时毒力也降低。在细胞壁胁迫条件下，Slt2的失活显著抑制了钙调神经磷酸酶介导的磷酸酶活性，表明这两条途径之间存在一定程度的相互作用。对Δslt2和Δcna1菌株的比较转录组分析揭示了不同基因集表达的变化，在参与细胞壁完整性、应激反应、分生孢子形成和毒力的转录本中有重叠。这些数据说明了球孢白僵菌中钙调神经磷酸酶和Slt2途径的趋同和不同表型及靶点。
