水稻多聚半乳糖醛酸酶抑制蛋白家族OsPGIP结构及基因表达特征 分析

Analysis on the structures of polygalacturonase-inhibiting proteins and the expression profile of its encoding genes in rice

Polygalacturonase-inhibiting protein, the extracellular leucine-rich repeat protein, specially recognizing and inhibiting polygalacturonase (PG) from pathogenic organism, can improve the resistance of plant against the pathogen. In order to clarify the structures of OsPGIPs and the expression profile of its encoding genes in rice, seven OsPGIP (polygalacturonase-inhibiting protein) genes were amplified from rice cDNA by PCR. Bioinformatics analysis and structural prediction of OsPGIPs were performed and expression profile of its encoding genes under biotic and abiotic stresses was determined after these genes being cloned and sequenced. The results showed that PGIPs from the same or similar species had high similarity. Through multi-sequence alignment and phylogenetic analysis, it was found that most OsPGIPs had closer genetic relationship, but all of them could not be grouped in one group. All OsPGIPs had a signal peptide and 9 to11 LRR fragments included the typical PGIP’s motif of xxLxLxx. Secondary structure prediction indicated that all OsPGIPs consist of ɑ-helix (H), extended strand (ES) and random coil (RC), which construct repeated RC-H-RC-ES- and form a typical concave coinciding with the right-hand helix rule. The concave might be responsible for the interaction between OsPGIPs and PGs from different agents. Most of the seven OsPGIPs were stable, and they all were hydrophobic proteins, good lipid solubility, with transmembrane structure, extrcellular localization, one or more N-glycosylation sites, and basically insoluble after expression in E. coli. After being treated with biotic and abiotic stress factors, the expression levels of different OsPGIP genes in rice were significantly up-regulated or down-regulated, but the total expression levels were significantly up-regulated, which indicated that rice could improve its own ability against stresses by regulating the expression levels of OsPGIP genes under stress conditions.