Signaling by the Pathogenicity-Related MAP Kinase of Cochliobolus heterostrophus Correlates With Its Local Accumulation Rather Than Phosphorylation
Signaling by the Pathogenicity-Related MAP Kinase of Cochliobolus heterostrophus Correlates With Its Local Accumulation Rather Than Phosphorylation
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DOI：
10.1094/mpmi-22-9-1093
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发表时间：
2009-09-01
影响因子：
3.5
通讯作者：
Horwitz, Benjamin A.
中科院分区：
文献类型：
--
作者：
Lev, Sophie;Tal, Hila;Horwitz, Benjamin A.
磷酸化丝裂原激活蛋白激酶 (MAPK) 通过激活其靶标来传递信号。信号转导的程度可能取决于 MAPK 磷酸化水平、浓度和亚细胞定位。玉米真菌病原体异旋旋孢菌的致病性 MAPK Chk1 是中央发育功能所必需的，包括附着胞形成、分生孢子形成、黑化、毒力和雌性生育力。我们跟踪了分生孢子在表面诱导附着胞形成和悬浮状态下萌发过程中的 CHK1 转录水平、蛋白质定位、数量、磷酸化和下游基因的表达。 Chk1-GFP 蛋白代表 Chk1 和 GFP（绿色荧光蛋白）的翻译融合，在未发芽的分生孢子中非常丰富，在成熟的附着胞和附着核中积累，但均匀分布在悬浮生长的菌丝中。 Chk1 依赖性基因的表达在附着胞形成菌丝中上调，但在悬浮菌丝中没有上调。尽管 Chk1 被激活，但其磷酸化和总蛋白量没有变化。在所有测试条件下，温度变化导致 Chk1 磷酸化减少，而高渗应激导致 Chk1 磷酸化增加。 Chk1 在附着胞形成过程中的激活显然是通过其局部积累来体现的，而不是通过磷酸化的显着变化来体现。
Phosphorylated mitogen-activated protein kinases (MAPK) transmit signals by activation of their targets. The extent of signal transduction could depend on MAPK phosphorylation level, concentration, and subcellular localization. The pathogenicity MAPK Chk1 of the fungal corn pathogen Cochliobolus heterostrophus is required for central developmental functions, including appressoria formation, conidiation, melanization, virulence, and female fertility. We followed CHK1 transcript level, protein localization, quantity, phosphorylation, and expression of downstream genes during conidial germination on a surface inductive for appressoria formation and in suspension. The Chk1-GFP protein representing a translational fusion of Chk1 and GFP (green fluorescent protein) was very abundant in ungerminated conidia, accumulated in maturating appressoria and appressorial nuclei, but was uniformly distributed in suspension-grown hyphae. Expression of Chk1-dependent genes was upregulated in appressoria-forming hyphae but not in suspension. Despite Chk1 activation, there was no change in its phosphorylation and total protein quantity. Of all conditions tested, a temperature shift caused a decrease whereas hyperosmotic stress caused an increase in Chk1 phosphorylation. Activation of Chk1 during appressoria formation is apparently manifested by its local accumulation but not by significant changes in phosphorylation.