Arrebola Eva, Cazorla Francisco M, Codina Juan C, Gutiérrez-Barranquero José A, Pérez-García Alejandro, de Vicente Antonio
Department of Microbiology, University of Málaga, Spain.
Int Microbiol. 2009 Jun;12(2):87-95.
Mangotoxin is an antimetabolite toxin that inhibits ornithine acetyl transferase, a key enzyme in the biosynthetic pathway of ornithine and arginine and recently reported in strains of Pseudomonas syringae pv. syringae (Pss) isolated from mango. Since symptoms on mango tissues are very difficult to reproduce, in this study the role of mangotoxin in Pss virulence was addressed by analyzing the in planta growth and development of disease symptoms on tomato leaflets. Inoculation experiments were carried out following several procedures using the wild-type strain Pss UMAF0158, two Tn5-mutant derivative strains defective in mangotoxin production, and their complemented derivative strains in which mangotoxin production is restored. The ability of the mangotoxin-defective mutants to grow in planta was similar, and their epiphytic survival on the tomato leaf surface identical to the wild-type and complemented strains. However, both the disease index data of incidence and the severity of necrotic symptoms indicated that mangotoxin-defective mutants were less virulent, indicating that mangotoxin is a virulence factor. Furthermore, competition experiments showed that the survival values of the wild-type strain were slightly but significantly higher than those of the mangotoxin-defective mutants, suggesting that mangotoxin production would improve the epiphytic fitness of Pss.
芒果毒素是一种抗代谢毒素，它能抑制鸟氨酸乙酰转移酶，该酶是鸟氨酸和精氨酸生物合成途径中的关键酶，最近在从芒果中分离出的丁香假单胞菌丁香致病变种（Pss）菌株中被报道。由于芒果组织上的症状很难重现，在本研究中，通过分析番茄小叶上病原菌在植物体内的生长情况和疾病症状的发展，来探讨芒果毒素在Pss致病力中的作用。使用野生型菌株Pss UMAF0158、两种芒果毒素产生缺陷的Tn5突变衍生菌株及其芒果毒素产生得以恢复的互补衍生菌株，按照几种程序进行接种实验。芒果毒素缺陷突变体在植物体内生长的能力相似，它们在番茄叶片表面的附生存活情况与野生型和互补菌株相同。然而，发病率的疾病指数数据和坏死症状的严重程度都表明，芒果毒素缺陷突变体的致病力较弱，这表明芒果毒素是一种致病因子。此外，竞争实验表明，野生型菌株的存活值略高于但显著高于芒果毒素缺陷突变体，这表明产生芒果毒素会提高Pss的附生适合度。
