摘要
硫是生物体必须的元素,根瘤菌结瘤因子的硫化修饰与其宿主范围和识别效率有着重要关系,实验室前期研究中突变费氏中华根瘤菌的cys DN基因后,突变体不能利用硫酸盐生长,这与Sinorhizobium sp.BR816的cys D基因突变后的现象不同,两株菌的硫酸盐同化途径中可能存在差异.为探讨不同根瘤菌cys DN基因对硫酸盐同化途径的影响,本研究利用同源交换的方法构建费氏中华根瘤菌WGF03、费氏中华根瘤菌HN01、苜蓿中华根瘤菌14500及大豆慢生根瘤菌15606的cys DN突变体,Δcys DN-WGF03、Δcys DN-HN01、Δcys DN-14500和cys NR-15606,对突变体的硫源利用情况和植株结瘤情况进行研究.结果发现,Δcys DN-WGF03和Δcys DN-HN01失去利用硫酸盐的能力;Δcys DN-14500能微弱地利用硫酸盐生长,生长量约为野生菌株的1/3左右;cys NR-15606对硫酸盐的利用与野生菌株相比无明显差别.植株实验结果显示,Δcys DN-WGF03、Δcys DN-HN01和Δcys DN-14500在平均瘤数、平均瘤重、平均植株干重和固氮酶活性方面均表现出显著降低,而突变体的回补体能够恢复硫酸盐的利用能力及与植株的共生固氮能力.这说明cys DN基因在费氏中华根瘤菌WGF03、费氏中华根瘤菌HN01和苜蓿中华根瘤菌14500硫酸盐同化途径中起着关键影响,而该基因在大豆慢生根瘤菌15606的影响并不明显.本研究表明,cys DN基因在不同根瘤菌中所起的作用不同,不同根瘤菌的硫酸盐同化方式也存在差异.
Sulfur is an essential element for organism, and sulfate modification of Nod factor plays a vital role in the host rangeand recognition efficiency. Our previous study constructed the mutants of Sinorhizobium fredii WGF03 through inactivating in cysDN by homologous single-crossover recombination. However, the cysDN mutants of S. fredii could not utilize sulfate as sulfur source, while the cysDN mutants of Sinorhizobium BR816 could grow weakly on medium with sulfate as sulfur source. This study aimed to understand the difference in activating sulfate by cysDN genes in different species of rhizobium. The cysDN mutants ofS. fredii WGF03, S. fredii HN01 S. meliloti 14500 and B. japonicum 15606 were constructed by using homologous recombination： AcvsDN-WGF03, AcysDN-HNO1, AcysDN-14500 and cvsNR -14500. Then the sulfur source utilization and plant tests of mutants were studied. The results showed that AcysDN-WGF03 and AcvsDN-HNOI could not grow on the medium of sulfate; AcysDN-14500 could grow on medium with sulfate as sulfur source, but with only 30% growth of the wild type strain; there was no obvious difference in utilization of various sulfur sources by cysNR-15606 and the wild strain. Plant tests showed that the plant inoculated with AcysDN-WGF03, AcysDN-HNO1 and A cysDN-14500 showed significantlylower average nodules number, nodules weight, plant dry weight and nitrogenase activity than wild type strains, but the complementary strains could restore the ability of using sulfate and plant symbiotic nitrogen fixation. The results indicated that cysDN genes play a key role in sulfate assimilation pathway of S. fredii WGF03, S. fredii HN01 and S. meliloti 14500, but not for B. japonicum 15606. Different species of rhizobium cysDN have different ways to activate sulfate.
出处
《应用与环境生物学报》
CAS
CSCD
北大核心
2015年第2期242-247,共6页
Chinese Journal of Applied and Environmental Biology
基金
国家重点基础研究发展计划项目(2010CB126502)资助~~
