水稻白叶枯病菌HD-GYP结构域蛋白PXO_03945的功能鉴定

为了揭示水稻白叶枯病菌(Xanthomonas oryzae pv.oryzae,简称Xoo)环二鸟苷酸(c-di-GMP)信号相关蛋白PXO_03945的生物学功能,本研究通过基因同源重组和无标记交换,对PXO_03945基因进行了缺失突变,对野生型、突变体和互补菌株进行表型测定,分析该基因缺失突变对病菌胞内c-di-GMP水平、致病性、运动性、胞外多糖产生和生物膜形成的影响。结果表明,PXO_03945蛋白具有参与c-di-GMP降解的磷酸二酯酶(PDE)的HD-GYP结构域和功能未知的DUF3391结构域。全长基因缺失可导致体内c-di-GMP浓度明显上升。与野生型相比,ΔPXO_03945对水稻品种日本晴的致病性显著下降,而游动性增强,胞外多糖产生和生物膜形成增加。基因互补可以使之恢复。因此,HD-GYP结构域蛋白PXO_03945可能通过降解胞内c-di-GMP,正向调控了致病性,负向调控了运动性、EPS产生和生物膜形成能力。

Functional identification of the HD-GYP domain protein PXO_03945 in Xanthomonas oryzae pv. oryzae

To reveal the biological functions of PXO_03945, one of the c-di-GMP signaling proteins in the bacterial blight pathogen of rice Xanthomonas oryzae pv. oryzae (Xoo), gene deletion mutagenesis via homologous recombination and non-marker exchange, complementation and phenotypic analysis were performed in this study. Bioinformatics analysis indicated that PXO_03945 was a HD-GYP and DUF3391 domain containing protein. In-frame deletion in PXO_03945 significantly led to increased intracellular c-di-GMP content. ΔPXO_03945 showed significantly decreased virulence on rice susceptible cultivar Nipponbare, and increased swimming motility, exopolysaccharide (EPS) production and biofilm formation compared to PXO99^A. In trans expression of the full length PXO_03945 in the mutant restored the phenotypes to near-wildtype levels. Therefore, PXO_03945 regulation of bacterial virulence, motility, EPS production and biofilm formation might be via c-di-GMP degradation by phosphodiesterase in Xoo.