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

在立枯丝核菌田间分离物中发现了发夹环质粒。在pRS 64 -1、pRS 64 - 2和pRS 64 - 3中发现的开放阅读框架（ORF 1 -1、ORF 2 -1和ORF 3 -1）分别为68个氨基酸长。ORF-1编码的氨基酸序列从N端开始显示MetThrLeuProLysAlaGlyAlapheThrAsnArgproAspArgArgLeupro-GlyValAsnSerAlaSerGlyAfgserTrpMetLysLeuproCysLysSerGluGlyAsnCysLEUSerMetProTrpGlyIleValLeuArgSerHisSerLeuSerGlyLeuAspArgLeuProLeuGGluProProLysValAla。这些ORF编码的氨基酸序列与已知蛋白没有明显的同源性。从表达ORF-1基因的大肠杆菌细胞中提取一种特异性的7 kDa新蛋白。抗pRS 64编码的蛋白（RS64）抗体产生的合成肽（35和33个氨基酸残基从ORF-1的N-和C-末端）与菌丝体中发现的特定蛋白质的交叉反应。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信号转导。也就是说，可能参与寄主识别和菌丝无丝孔形成的特异蛋白质在茄立枯丝核菌中通过发夹环线性质粒表达。

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.