PDF(Pubmed)
Abstract：
Ras GTPase-activating proteins (Ras GAPs) act as negative regulators for Ras proteins and are involved in various signalling processes that influence cellular functions. Here, the function of four Ras GAPs, UvGap1 to UvGap4, was identified and analysed in Ustilaginoidea virens, the causal agent of rice false smut disease. Disruption of UvGAP1 or UvGAP2 resulted in reduced mycelial growth and an increased percentage of larger or dumbbell-shaped conidia. Notably, the mutant ΔUvgap1 completely lost its pathogenicity. Compared to the wild-type strain, the mutants ΔUvgap1, ΔUvgap2 and ΔUvgap3 exhibited reduced tolerance to H2 O2 oxidative stress. In particular, the ΔUvgap1 mutant was barely able to grow on the H2 O2 plate, and UvGAP1 was found to influence the expression level of genes involved in reactive oxygen species synthesis and scavenging. The intracellular cAMP level in the ΔUvgap1 mutant was elevated, as UvGap1 plays an important role in maintaining the intracellular cAMP level by affecting the expression of phosphodiesterases, which are linked to cAMP degradation in U. virens. In a yeast two-hybrid assay, UvRas1 and UvRasGef (Ras guanyl nucleotide exchange factor) physically interacted with UvGap1. UvRas2 was identified as an interacting partner of UvGap1 through a bimolecular fluorescence complementation assay and affinity capture-mass spectrometry analysis. Taken together, these findings suggest that the UvGAP1-mediated Ras pathway is essential for the development and pathogenicity of U. virens.
摘要：
RasGTP酶激活蛋白（RasGAP）充当Ras蛋白的负调节因子，并参与影响细胞功能的各种信号过程。这里,四个RasGAP的功能，UvGap1至UvGap4，在Ustilaginoidea病毒中进行了鉴定和分析，水稻假黑穗病的病原体。UvGAP1或UvGAP2的破坏导致菌丝体生长减少，较大或哑铃形分生孢子的百分比增加。值得注意的是,突变体ΔUvgap1完全失去致病性。与野生型菌株相比，突变体ΔUvgap1，ΔUvgap2和ΔUvgap3对H2O2氧化应激的耐受性降低。特别是,ΔUvgap1突变体几乎不能在H2O2板上生长，发现UvGAP1影响与活性氧合成和清除有关的基因的表达水平。ΔUvgap1突变体的细胞内cAMP水平升高,由于UvGap1通过影响磷酸二酯酶的表达在维持细胞内cAMP水平中起重要作用，这与U.virens中的cAMP降解有关。在酵母双杂交试验中，UvRas1和UvRasGef(Ras鸟苷酸交换因子)与UvGap1物理相互作用。通过双分子荧光互补测定和亲和捕获-质谱分析将UvRas2鉴定为UvGap1的相互作用伴侣。一起来看,这些研究结果表明，UvGAP1介导的Ras通路对U.virens的发展和致病性至关重要。
