Sukchawalit R, Vattanaviboon P, Utamapongchai S, Vaughn G, Mongkolsuk S
Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand.
FEMS Microbiol Lett. 2001 Nov 27;205(1):83-9. doi: 10.1111/j.1574-6968.2001.tb10929.x.
Analysis of the nucleotide sequence downstream from the Xanthomonas oryzae pv. oryzae recA gene reveals two orfs designated orfX and recX. The former has the potential to code for a 5.6 kDa protein of unknown function while the latter encodes for a putative 14.6 kDa protein with homology to RecX from various bacteria. Northern blot analysis and RT-PCR results show that recA-orfX-recX are co-regulated and arranged in an operon. A recX mutant was constructed. The mutant has no obvious growth defects or stress response defects, except that it cannot support high-level expression of recA from an expression vector. Introduction of the plasmid containing recA into the recX mutant resulted in reduced transformation efficiency and all transformants tested had mutations with reduced RecA levels. Moreover, the recX mutant has reduced basal levels of RecA. This has not been observed in other bacteria. When inactivated recX was complemented in trans, both changes were reversed. recX mutation has no effect on the regulation of the recA promoter, suggesting that its effect on the RecA level could be post-transcriptional.
对水稻白叶枯病菌recA基因下游的核苷酸序列分析揭示了两个开放阅读框，分别命名为orfX和recX。前者有可能编码一个功能未知的5.6 kDa蛋白，而后者编码一个假定的14.6 kDa蛋白，与来自各种细菌的RecX具有同源性。Northern印迹分析和RT-PCR结果表明，recA-orfX-recX是共调控的，并排列在一个操纵子中。构建了一个recX突变体。该突变体没有明显的生长缺陷或应激反应缺陷，只是它不能支持来自表达载体的recA的高水平表达。将含有recA的质粒导入recX突变体导致转化效率降低，并且所有测试的转化体都有RecA水平降低的突变。此外，recX突变体的RecA基础水平降低。这在其他细菌中尚未观察到。当反式互补失活的recX时，这两种变化都被逆转。recX突变对recA启动子的调控没有影响，表明其对RecA水平的影响可能是转录后水平的。
