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

植物多聚半乳糖醛酸酶抑制蛋白(polygalacturonase-inhibitingprotein,PGIP)可特异性识别病原菌PG(polygalacturonase),从而提高植物的抗病能力。研究表明水稻中共存在7个OsPGIP基因,为明确OsPGIP家族的蛋白质结构及基因表达特征,从水稻cDNA中扩增各OsPGIP基因序列,经克隆、测序后进行生物信息学分析与蛋白质结构模拟,并测定其在生物逆境与非生物逆境胁迫下的表达量变化。经多序列比较与系统发育进化分析发现,相同或相近物种PGIP往往具有较高的相似性,虽然多数OsPGIP亲缘关系较近,但它们并不能完全聚类在一起。7个OsPGIP蛋白均具有一个信号肽和9~11个LRR片段,各LRR片段中均含有PGIP的特征结构域xxLxLxx。二级结构由α-螺旋、β-折叠和随机卷曲组成,且多以随机卷曲为主,这些二级结构以重复的随机卷曲—α-螺旋—随机卷曲—β-折叠组成线圈状结构,并按右手螺旋规则形成一个特定的凹面,负责OsPGIP与有害生物PG的互作。7个OsPGIP蛋白多较稳定,且均为疏水蛋白、脂溶性好、具有跨膜结构、定位于细胞外、有1到多个N-糖基化位点、在大肠杆菌中原核表达后基本不溶。经生物和非生物逆境处理后,水稻中不同OsPGIP基因的表达量上下调差异较大,但表达量总和明显上调,说明在逆境条件下水稻可通过调节自身OsPGIP基因的表达量,从而提高其抗逆性。

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 ofɑ-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.