柑桔潰瘍病原菌非致病突變株之特性分析

Abstract

柑桔潰瘍病原菌（Xanthomonas campestris pv. citri）是一種植物致病菌，會造成柑桔類植物的柑桔潰瘍病。利用轉位子Tn5tac1誘導X. c. pv. citri突變得到的突變株XT-906無病徵表現，是屬於無致病能力（non-pathogenicity, NP）的突變株。 本研究以XT-906（NP）突變株為研究材料，分離被Tn5tac1破壞的致病相關基因：首先建立野生型X. c. pv. citri（XW47）與突變株XT-906的基因庫；再利用Tn5tac1為標記，由突變株基因庫中篩選出帶有Tn5tac1及部分X. c. pv. citri DNA片段的選殖株。進一步在野生型基因庫中篩選到包含此致病相關基因片段的選殖株。而後建立此DNA片段的限制脢圖譜及定出部分DNA序列；另外，測定突變株XT-906細胞外分泌性酵素的活性，包括：澱粉水解脢、蛋白質分解脢及果膠分解脢，發現和野生型XW47並無差異。

Xanthomonas campestris pv. citri (X. c. pv. citri) is a phytopathogenic bacterium resulting the citrus canker disease. A non-pathogenic mutant, XT-906, of X. c. pv. citri was isolated by Tn5tac1 insertional mutagenesis. To study the pathogenesis regulation of XT-906, genomic libraries of wild type X. c. pv. citri and XT-906 were constructed. The Tn5tac1 containing clone was initially isolated from the XT-906 library. DNA fragments surrounding the transposon were determined and used as the probe to further isolate gene(s) conferring to the non-pathogenic phenotypes of XT-906 from the wild type library. Secretary enzymes such as amylase, protease and pectate lyase of XT-906 have been detected. However there is no significant difference in the activity of these extracellular enzymes between the XT-906 mutant and the wild type Xanthomonas.