Divergent cAMP signaling pathways regulate growth and pathogenesis in the rice blast fungus Magnaporthe grisea
Divergent cAMP signaling pathways regulate growth and pathogenesis in the rice blast fungus Magnaporthe grisea
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DOI：
10.1105/tpc.10.8.1361
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发表时间：
1998-08-01
期刊：
影响因子：
11.6
通讯作者：
Hamer, JE
中科院分区：
文献类型：
--
作者：
Adachi, K;Hamer, JE
CAMP参与了稻瘟病菌附着胞形成的信号转导。然而，蛋白激酶A(PKA)催化亚基基因CPKA的零突变并不阻止附着胞的形成，而腺苷环化酶基因的突变对生长、分生孢子、性发育和附着胞的形成具有多效性。因此，cAMP信号在生长和形态发生以及附着胞的形成中都起着重要作用。为了阐明稻瘟病菌中的cAMP信号，我们鉴定了腺苷环化酶基因(MAC1)零突变具有不稳定表型的菌株，以便能够识别MAC1(-)表型(SUM)的旁路抑制因子。SUM突变完全恢复生长、有性和无性形态发生，并导致在抑制野生型的条件下形成附着体的能力。PKA分析和分子克隆表明，一个抑制子突变(Sum1-99)改变了PKA调节亚单位基因(Sum1)cAMP结合域A中的保守氨基酸，而其他抑制子突变的作用不依赖于PKA活性。PKA分析表明，催化亚单位基因CPKA编码稻瘟病菌中唯一可检测到的PKA活性。由于CPKA对于生长、形态发生和附着胞的形成是必不可少的，不同的催化亚单位基因必须在这些过程中发挥作用。这些结果提示了一种模型，在该模型中，稻瘟病菌的腐生性生长和病原性生长均由腺苷环化酶调控，但不同的cAMP效应因子介导了特定于细胞形态发生或致病的下游效应。
cAMP is involved in signaling appressorium formation in the rice blast fungus Magnaporthe grisea. However, null mutations in a protein kinase A (PKA) catalytic subunit gene, CPKA, do not block appressorium formation, and mutations in the adenylate cyclase gene have pleiotropic effects on growth, conidiation, sexual development, and appressorium formation. Thus, cAMP signaling plays roles in both growth and morphogenesis as well as in appressorium formation. To clarify cAMP signaling in M. grisea, we have identified strains in which a null mutation in the adenylate cyclase gene (MAC1) has an unstable phenotype such that the bypass suppressors of the Mac1(-) phenotype (sum) could be identified. sum mutations completely restore growth and sexual and asexual morphogenesis and lead to an ability to form appressoria under conditions inhibitory to the wild type. PKA assays and molecular cloning showed that one suppressor mutation (sum1-99) alters a conserved amino acid in cAMP binding domain A of the regulatory subunit gene of PKA (SUM1), whereas other suppressor mutations act independently of PKA activity. PKA assays demonstrated that the catalytic subunit gene, CPKA, encodes the only detectable PKA activity in M. grisea. Because CPKA is dispensable for growth, morphogenesis, and appressorium formation, divergent catalytic subunit genes must play roles in these processes. These results suggest a model in which both saprophytic and pathogenic growth of M. grisea is regulated by adenylate cyclase but different effecters of cAMP mediate downstream effects specific for either cell morphogenesis or pathogenesis.