瓜类细菌性果斑病菌(Acidovorax citrulli,Ac)是近年来发生在西瓜、甜瓜等葫芦科植物上的一种重要病原细菌。它主要危害西瓜、甜瓜,引起叶斑或叶枯,造成果实腐烂,严重时导致绝产。【目的】验证组氨酸的合成缺陷与Ac的致病性之间的关系。【方法】采用Mini-Tn5转座子随机插入方法,从瓜类细菌性果斑病菌xjl12突变体文库中筛选突变体,并通过亚克隆技术对基因进行鉴定。【结果】筛选到一株在烟草上失去过敏反应且致病性降低的突变体。鉴定其为hisC(histidinol-phosphate aminotransferase)基因的突变体。同时也对Ac中组氨酸合成过程中的另外3个酶(hisA、hisB和hisD基因)进行了研究。这些基因突变后均丧失了激发烟草过敏性反应的能力,致病性明显下降,发病时间比野生型延迟了约48 h,通过外源添加组氨酸可恢复其突变特征。【结论】这些基因的突变所致性状改变与组氨酸的合成缺陷直接相关。 Acidovorax citrulli (Ac) is a kind of important pathogenic bacteria that occurred in watermelon, melon and other cucurbits in recent years. It is mainly harmful to watermelons, melons, causing leaf spots or leaf blight, causing fruit decay, serious lead to abortion. 【Objective】 To verify the relationship between histidine synthesis and Ac pathogenicity. 【Method】 The mutants were screened from Cucurbitacum sp. Xjl12 mutant library by Mini-Tn5 transposon insertion method. The genes were identified by subcloning technique. 【Result】 A mutant with reduced allergenicity and reduced pathogenicity in tobacco was screened out. It was identified as a mutant of the hisC (histidinol-phosphate aminotransferase) gene. Three additional enzymes (hisA, hisB and hisD genes) in histidine synthesis in Ac were also studied. After mutation, all of them lost the ability to stimulate the hypersensitive response of tobacco and the pathogenicity decreased obviously. The onset time was delayed about 48 hours later than the wild type, and the mutation characteristics were restored by the addition of histidine. 【Conclusion】 Mutations induced by these genes are directly related to histidine synthesis defects.