Erental A, Harel A, Yarden O
Department of Plant Pathology and Microbiology, The Minerva Center for Agricultural Biotechnology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.
Mol Plant Microbe Interact. 2007 Aug;20(8):944-54. doi: 10.1094/MPMI-20-8-0944.
Sclerotinia sclerotiorum is a necrotrophic, omnivorous plant pathogen with worldwide distribution. Sclerotia of S. sclerotiorum are pigmented, multihyphal structures that play a central role in the life and infection cycles of this pathogen. Plant infection depends on the formation of melanin-rich infection cushions, and secretion of hydrolytic enzymes and oxalic acid. Type 2A Ser/Thr phosphatases (PP2As) are involved in the regulation of a variety of cellular process. In the presence of cantharidin, a PP2A-specific inhibitor, hyphal elongation and sclerotia numbers were impaired whereas sclerotial size increased. We partially inactivated PP2A by antisense expression of the gene (pph1) encoding the PP2A catalytic subunit. When antisense expression was induced, almost complete cessation of fungal growth was observed, indicative of a crucial role for PP2A in fungal growth. RNAi-based gene silencing was employed to alter the expression of the 55-kDa R2 (B regulatory subunit). Isolates in which rgb1 RNA levels were decreased were slow growing, but viable. Melanin biosynthesis, infection-cushion production, and pathogenesis were significantly impaired in the rgb1 mutants, yet theses mutants were pathogenic on wounded leaves. Reduced ERK (extracellular signal-regulated kinases)-like mitogen-activated protein kinase (MAPK) function conferred a reduction in NADPH oxidase and PP2A activity levels, suggesting a functional link between MAPK, reactive oxygen species, and PP2A activity in S. sclerotiorum.
核盘菌是一种腐生性、多食性植物病原菌，在全球范围内均有分布。核盘菌的菌核是有色素的多菌丝结构，在该病原菌的生活和侵染循环中起着核心作用。植物感染取决于富含黑色素的侵染垫的形成，以及水解酶和草酸的分泌。2A型丝氨酸/苏氨酸磷酸酶（PP2A）参与多种细胞过程的调控。在PP2A特异性抑制剂斑蝥素存在的情况下，菌丝伸长和菌核数量受到损害，而菌核大小增加。我们通过编码PP2A催化亚基的基因（pph1）的反义表达部分失活了PP2A。当诱导反义表达时，观察到真菌生长几乎完全停止，这表明PP2A在真菌生长中起关键作用。基于RNA干扰的基因沉默被用于改变55 kDa R2（B调节亚基）的表达。rgb1 RNA水平降低的分离株生长缓慢，但仍可存活。rgb1突变体中黑色素生物合成、侵染垫产生和致病力均显著受损，但这些突变体在受伤叶片上仍具有致病性。细胞外信号调节激酶（ERK）样丝裂原活化蛋白激酶（MAPK）功能的降低导致NADPH氧化酶和PP2A活性水平降低，这表明核盘菌中MAPK、活性氧和PP2A活性之间存在功能联系。
