Structural analysis and signal transduction of the host recognition factors expressed in hairpin loop linear DNA plasmid in the plant pathogenic fungus

在立枯丝核菌的田间分离物中发现了发夹环质粒。PRS64-1、-2和-3(ORF1-1、ORF2-1和ORF3-1)的开放阅读框长度分别为68个氨基酸。ORF-1编码的氨基酸序列显示N端有MetThrLeuProLysAlaGlyAlapheThrAsnArgproAspArgArgLeupro-GlyValAsnSerAlaSerGlyAfgserTrpMetLysLeuproCysLysSerGluGlyAsnCysLEUSerMetProTrpGlyIleValLeuArgSerHisSerLeuSerGlyLeuAspArgLeuProLeuGGluProProLysValAla。这些ORF编码的氨基酸序列与已知的蛋白质没有明显的同源性。表达7 kDa特异新蛋白ORF-1基因的大肠杆菌提取液。针对合成肽(来自ORF-1 N端和C端的35和33个氨基酸残基)产生的抗pRS64编码蛋白(Rs64)抗体与菌丝体中发现的特定蛋白发生交叉反应。Rs64蛋白定位于菌丝体细胞壁。结果表明，Rs64蛋白中的单个富含亮氨酸的基序参与了蛋白质间的相互作用和转导。换句话说，可能参与寄主识别和菌丝融合的特定蛋白质是通过发夹环线状质粒在水稻纹枯病菌中表达的。

Hairpin loop plasmids were found in the field isolate of Rhizoctonia solani. The open reading frames found in pRS64-1, -2, and -3 (ORF1-1, ORF2-1, and ORF3-1) were 68 amino acid long, respectively. The amino acid sequence encoded by the ORF-1 showed MetThrLeuProLysAlaGlyAlapheThrAsnArgproAspArgArgLeupro-GlyValAsnSerAlaSerGlyAfgserTrpMetLysLeuproCysLysSerGluGlyAsnCysLEUSerMetProTrpGlyIleValLeuArgSerHisSerLeuSerGlyLeuAspArgLeuProLeuGGluProProLysValAla from N-terminal. The amino acid sequence encodid by these ORFs showed no significant homology with known proteins. Extracts from Escherichia coli cells expressing ORF-1 gene a specific new protein of 7 kDa. Anti-pRS64-encoded protein (RS64) antibodies raised against the synthetic peptide (35 and 33 aminoacid residues from ORF-1 N-and C-terminal) cross-reacted with the specific protein found in the mycelia. RS64 protein is located in cell wall of the mycelia. The results indicate that the single leucine-rich motif in RS64 protein involved in protein-protein interactions and transduction. In other words, the specific protein, which may be involved in the host recognition and the hyphal asnastomosis, was expressed by the hairpin loop linear plasmids in R.solani.