Evidence for HrpXo-dependent expression of type II secretory proteins in Xanthomonas oryzae pv. oryzae
Evidence for HrpXo-dependent expression of type II secretory proteins in Xanthomonas oryzae pv. oryzae
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DOI：
10.1128/jb.186.5.1374-1380.2004
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发表时间：
2004-03-01
影响因子：
3.2
通讯作者：
Kubo, Y
中科院分区：
文献类型：
--
作者：
Furutani, A;Tsuge, S;Kubo, Y
水稻白稻是水稻细菌性叶枯病的病原体。近年来，人们建立了一种高效的hrp诱导培养基XOM 2。在该培养基中，野生型X. oryzaepv.米。当与hrp调节基因中具有突变的菌株一起孵育时，这些蛋白质中的许多在XOM 2上的培养物中消失或数量减少。有趣的是，除了一些蛋白质消失外，缺乏由hrp基因编码的III型分泌系统（TTSS）的突变株的分泌蛋白质谱与野生型菌株的分泌蛋白质谱相似。这一发现表明许多HrpXo依赖性分泌蛋白通过TTSS以外的系统分泌。通过分离缺乏II型分泌系统的突变株，我们检验了这一假设。与预期的一样，当突变体在XOM 2中培养时，许多HrpXO依赖性分泌蛋白消失或减少。通过测定N-末端氨基酸序列，我们鉴定了一种II型分泌蛋白为半胱氨酸蛋白酶同源物CysP 2。核苷酸序列分析表明，cysP 2具有一个不完全的植物诱导型启动子盒，启动子区具有HrpXo调控子的共有序列，N端具有一个推导的信号肽序列。通过逆转录PCR分析和使用含有cysP 2 ∷ gus融合基因的质粒检测CysP 2的表达，证实了CysP 2的HrpXO依赖性表达。在此，我们揭示hrp调节基因hrpXO不仅参与hrp基因和III型分泌蛋白的表达，而且还参与一些II型分泌蛋白的表达。
Xanthomonas oryzae pv. oryzae is a causal agent of bacterial leaf blight of rice. Recently, an efficient hrp-inducing medium, XOM2, was established for this bacterium. In this medium, more than 10 proteins were secreted from the wild-type strain of X. oryzae pv. oryzae. Many of these proteins disappeared or decreased in amount in culture on XOM2 when incubated with the strain that has a mutation in the hrp regulatory gene. Interestingly, the secretory protein profile of a mutant lacking a type III secretion system (TTSS), components of which are encoded by hrp genes, was similar to that of the wild-type strain except that a few proteins had disappeared. This finding suggests that many HrpXo-dependent secretory proteins are secreted via systems other than the TTSS. By isolating mutant strains lacking a type II secretion system, we examined this hypothesis. As expected, many of the HrpXo-dependent secretory proteins disappeared or decreased when the mutant was cultured in XOM2. By determining the N-terminal amino acid sequence, we identified one of the type II secretory proteins as a cysteine protease homolog, CysP2. Nucleotide sequence analysis revealed that cysP2 has an imperfect plant-inducible-promoter box, a consensus sequence which HrpXo regulons possess in the promoter region, and a deduced signal peptide sequence at the N terminus. By reverse transcription-PCR analysis and examination of the expression of CysP2 by using a plasmid harboring a cysP2::gus fusion gene, HrpXo-dependent expression of CysP2 was confirmed. Here, we reveal that the hrp regulatory gene hrpXo is also involved in the expression of not only hrp genes and type III secretory proteins but also some type II secretory proteins.