Involvement of Botrytis cinerea Small GTPases BcRAS1 and BcRAC in Differentiation, Virulence, and the Cell Cycle
Involvement of Botrytis cinerea Small GTPases BcRAS1 and BcRAC in Differentiation, Virulence, and the Cell Cycle
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DOI：
10.1128/ec.00160-13
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发表时间：
2013-12-01
期刊：
影响因子：
--
通讯作者：
Sharon, Amir
中科院分区：
文献类型：
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作者：
Dub, Anna Minz;Kokkelink, Leonie;Sharon, Amir
Ras超家族的小GTP酶是高度保守的蛋白质，参与多种细胞过程，特别是形态发生、分化和极地生长。在这里，我们报告了灰霉菌灰霉病菌的RAS1和RAC同源物的分析。我们发现，这些小的GTP酶是极地生长、繁殖和致病所必需的，是通过有丝分裂(BcRAC)进行细胞周期进程所必需的，并且可能位于应激相关丝裂原激活蛋白激酶(MAPK)信号通路的上游。Bcras1和bcrc缺失菌株生长速度减慢，菌丝超分枝变形。此外，这两个菌株都是营养不育和非致病的。表达BcRAC蛋白的成分活性(CA)等位基因的菌株具有部分相似但较温和的表型。与缺失菌株相似，CA-BcRAC菌株不产生分生孢子，菌丝肿胀。然而，与这两个缺失菌株相比，CA-BcRAC菌株的生长速度是正常的，它会引起延迟但发育良好的疾病症状。显微镜检查显示，CA-BcRAC株的细胞核数量增加，肌动蛋白定位紊乱。进一步研究细胞周期和RAC特异的抑制化合物使BcRAC蛋白通过有丝分裂与细胞周期的进展联系起来，可能是通过对微管的影响。综上所述，这些结果表明，CA-BcRAC株的多核表型可能至少由两个缺陷造成：由于肌动蛋白定位的干扰而破坏了极地生长，以及由于BcRAC的构成活性而导致核分裂失控。
Small GTPases of the Ras superfamily are highly conserved proteins that are involved in various cellular processes, in particular morphogenesis, differentiation, and polar growth. Here we report on the analysis of RAS1 and RAC homologues from the gray mold fungus Botrytis cinerea. We show that these small GTPases are individually necessary for polar growth, reproduction, and pathogenicity, required for cell cycle progression through mitosis (BcRAC), and may lie upstream of the stress-related mitogen-activated protein kinase (MAPK) signaling pathway. bcras1 and bcrac deletion strains had reduced growth rates, and their hyphae were hyperbranched and deformed. In addition, both strains were vegetatively sterile and nonpathogenic. A strain expressing a constitutively active (CA) allele of the BcRAC protein had partially similar but milder phenotypes. Similar to the deletion strains, the CA-BcRAC strain did not produce any conidia and had swollen hyphae. In contrast to the two deletion strains, however, the growth rate of the CA-BcRAC strain was normal, and it caused delayed but well-developed disease symptoms. Microscopic examination revealed an increased number of nuclei and disturbance of actin localization in the CA-BcRAC strain. Further work with cell cycle-and RAC-specific inhibitory compounds associated the BcRAC protein with progression of the cell cycle through mitosis, possibly via an effect on microtubules. Together, these results show that the multinucleate phenotype of the CA-BcRAC strain could result from at least two defects: disruption of polar growth through disturbed actin localization and uncontrolled nuclear division due to constitutive activity of BcRAC.