小孢子链格孢endoPG基因核苷酸序列分析及系统发育研究

Sequence and phylogenetic analysis of endopolygalacturonase genes from Alternaria small-spored species

对供试小孢子链格孢菌株的内聚半乳糖醛酸酶(endoPG)基因进行扩增,大部分菌株都可获得PCR产物。核苷酸和氨基酸序列比较表明:不同种小孢子链格孢endoPG基因核苷酸序列存在明显差异,甚至表现在氨基酸水平,这些差异可以作为一些种如梨黑斑链格孢、长柄链格孢区分的分子性状。利用邻近结合法构建系统发育树,所有菌株被分为8个聚类组。在系统发育树上,链格孢的一些不同分离物被聚在不同组中,而细极链格孢、链格孢的部分菌株、苹果链格孢、柑橘链格孢、粗柠檬褐斑链格孢、橘树链格孢被聚为一组,显示根据形态学特征划分的这些种与分子性状的不一致性。endoPG基因核苷酸序列富于变化,为小孢子链格孢系统发育研究提供了一种有用的手段。

EndoPG genes of small-spored Alternaria species were amplified with specific primer pairs, most of strains could produce a single same size band. Nucleotide acid and amino acid sequences were compared. It was found that there were some differences in nucleotide and amino acid sequences among the species, such as Alternaria longipes and A. gaisen. Phylogenetic tree were constructed using neighbor-joining method, all of the isolates were distributed in eight clades. Isolates of A. alternata were clustered into different groups, but A. tenuissima, A. mali, A. cirri, A. limoniasperae, A. citriarbusti were assembled to a same group, it showed the species segregation incongruence based on unstable morphological characters and molecular data. There are great variations among the small-spored Alternaria species of the endoPG gene sequences, which could provide useful information for phylogenetics of small-spored Alternaria species.