The Sinorhizobium (Ensifer) fredii HH103 rkp-2 region is involved in the biosynthesis of lipopolysaccharide and exopolysaccharide but not in K-antigen polysaccharide production
The Sinorhizobium (Ensifer) fredii HH103 rkp-2 region is involved in the biosynthesis of lipopolysaccharide and exopolysaccharide but not in K-antigen polysaccharide production
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DOI：
10.1007/s11104-017-3268-z
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发表时间：
2017-08-01
期刊：
影响因子：
4.9
通讯作者：
Vinardell, Jose-Maria
中科院分区：
文献类型：
--
作者：
Acosta-Jurado, Sebastian;Navarro-Gomez, Pilar;Vinardell, Jose-Maria
根瘤菌表面多糖是与豆科植物成功共生所需的重要分子决定因素。在Sinorhizobium (Ensifer) meliloti Rm41中，rkp-2区域参与k抗原多糖（KPS）和脂多糖（LPS）的生物合成。该区域由lpsL和rkpK两个基因组成，分别负责半乳糖醛酸和葡萄糖醛酸的产生。在这项工作中，我们发现在S. (Ensifer) fredii HH103中，这些基因不形成转录单位，并且rkpK的转录率远高于lpsL。这些基因的失活导致LPS的改变，但不影响KPS的产生，这与fredii HH103 KPS中缺乏醛酸一致。rkpK突变也会损害HH103胞外多糖（EPS）的产生，这很可能是由于HH103胞外多糖中葡萄糖醛酸的存在，以及细菌自聚集和渗透敏感性的增加和塑料表面生物膜形成的减少。rkpK失活对豇豆的共生产生负向影响，但对大豆的共生没有影响。lpsL突变导致与豇豆的共生完全受损，而接种该突变体的大豆植株只形成假结节。在两株植物中，lpsL突变体在根侵染方面都表现出缺陷。这些结果证实了HH103 LPS在与豆科植物共生中的重要作用。
Rhizobial surface polysaccharides are important molecular determinants required for successful symbiosis with legumes. In Sinorhizobium (Ensifer) meliloti Rm41, the rkp-2 region is involved in the biosynthesis of K-antigen polysaccharide (KPS) and lipopolysaccharide (LPS). This region is composed of two genes, lpsL and rkpK, which are respectively responsible for the production of galacturonic and glucuronic acid.In this work, we show that in S. (Ensifer) fredii HH103 these genes do not form a transcriptional unit and that the transcriptional rate of rkpK is much higher than that of lpsL. Inactivation of each of these genes resulted in alterations in LPS, but did not affect KPS production, which is in agreement with the lack of uronic acids in S. fredii HH103 KPS. Mutation of rkpK also impaired HH103 exopolysaccharide (EPS) production, most probably due to the presence of glucuronic acid in HH103 EPS, as well as increased bacterial autoaggregation and osmosensitivity and decreased biofilm formation on plastic surfaces. Inactivation of rkpK affected negatively symbiosis with cowpea but not with soybean. Mutation of lpsL led to a complete symbiotic impairment with cowpea, whereas soybean plants inoculated with this mutant only formed pseudonodules. In both plants, the lpsL mutant showed defects in root infection.These results confirm the symbiotic importance of HH103 LPS in symbiosis with legumes.