Characterization and evolutionary analysis of a large polygalacturonase gene family in the oomycete plant pathogen Phytophthora cinnamomi
Characterization and evolutionary analysis of a large polygalacturonase gene family in the oomycete plant pathogen Phytophthora cinnamomi
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DOI：
10.1094/mpmi.2002.15.9.907
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发表时间：
2002-09-01
影响因子：
3.5
通讯作者：
Hardham, AR
中科院分区：
文献类型：
--
作者：
Götesson, A;Marshall, JS;Hardham, AR
多聚半乳糖醛酸酶（Polygalacturonases，PGs）是真菌病原体在寄生和寄生生长过程中分泌的一类酶，其降解植物细胞壁中的果胶被认为在组织入侵和浸渍中起主要作用。在这项研究中，PG活性证明在培养菌丝体植物病原体，Phytophthora cinnamomi。根据真菌和植物PG的保守区设计简并引物，扩增肉桂疫霉PG基因片段，从基因组文库中分离出17个完整的肉桂疫霉PG基因和假基因，并对另外2个基因进行了部分序列测定。基因组DNA的凝胶印迹分析表明，在樟芝基因组中可能存在更多的pg基因。R cinnamomi PG基因序列在PG缺陷型酵母中表达，并发现赋予PG活性，从而确认其功能特性。预测的成熟R cinnamomi PG落入亚组，表现出很大的差异，在N-糖基化的程度，等电点，和N-和C-末端结构。在肉桂P PG基因家族中获得了出生和死亡和网状进化的证据，并且在肉桂P PG中的表面暴露残基的一些密码子被证明已经受到多样化选择。相反，接受其他蛋白质的同源性，系统发育分析的R cinnamomi PG揭示了一个更密切的关系，从真正的真菌PG比那些从植物。
Polygalacturonases (PGs) are secreted by fungal pathogens during saprophytic and parasitic growth, and their degradation of pectin in the plant cell wall is believed to play a major role in tissue invasion and maceration. In this study, PG activity was demonstrated in culture filtrates of the oo-mycete plant pathogen, Phytophthora cinnamomi. A P. cinnamomi pg gene fragment amplified using degenerate primers based on conserved regions in fungal and plant PGs was used to isolate 17 complete P cinnamomi pg genes and pseudogenes from a genomic library and partial sequence for another two genes. Gel blotting of genomic DNA indicated that there may be even more pg genes in the P cinnamomi genome. R cinnamomi pg gene sequences were expressed in PG-deficient yeast and found to confer PG activity, thereby confirming their functional identity. The predicted mature R cinnamomi PGs fall into subgroups that exhibit large differences in the extent of N-glycosylation, isoelectric points, and N- and C-terminal structure. Evidence for birth-and-death and reticulate evolution in the P cinnamomi pg gene family was obtained, and some codons for surface exposed residues in the P cinnamomi PGs were shown to have been subject to diversifying selection. Contrary to accepted phylogenies for other proteins, phylogenetic analysis of the R cinnamomi PGs revealed a closer relationship with PGs from true fungi than with those from plants.