在固氮酶阳性、固氮阴性的日本慢生根瘤菌变体中的固氮基因表达

nif gene expression in a Nif+, Fix- Bradyrhizobium japonicum variant.

作者信息

Bradburne J A, Mathis J N, Israel D W

机构信息

School of Biology, Georgia Institute of Technology, Atlanta.

出版信息

FEMS Microbiol Lett. 1994 Oct 15;123(1-2):91-8. doi: 10.1016/0378-1097(94)90279-8.

DOI:10.1016/0378-1097(94)90279-8

PMID:7988904

Abstract

Bradyrhizobium japonicum USDA 110 has been shown to contain several genetically similar, naturally occurring colony morphology variants. One of these variants, L2-110, although devoid of symbiotic nitrogen fixation, retains significant levels of ex planta nitrogen fixation ability relative to other symbiotically competent USDA 110 variants (MN-110 and I-110). Interestingly, Northern blot analyses revealed that L2-110 nodules, despite their lack of symbiotic nitrogen fixation, contained 65% the level of mRNA for dinitrogenase (nif DK) and 64% the level of dinitrogenase reductase (nif H) mRNA relative to MN-110 nodules. Western blot analyses of tissue from the same nodules detected 32% the level of dinitrogenase and 31% the level of dinitrogenase reductase in L2-110 relative to MN-110. L2-110 appears to be a new class of mutant based on the complete absence of symbiotic nitrogen fixation (Fix-) and the presence of significant ex planta nitrogen fixation (Nif+).

摘要

日本慢生根瘤菌USDA 110已被证明含有几种遗传相似的、自然存在的菌落形态变体。其中一种变体L2 - 110，虽然缺乏共生固氮能力，但相对于其他具有共生能力的USDA 110变体（MN - 110和I - 110），其体外固氮能力仍保持在相当水平。有趣的是，Northern印迹分析显示，尽管L2 - 110根瘤缺乏共生固氮能力，但相对于MN - 110根瘤，其固氮酶（nif DK）的mRNA水平为MN - 110根瘤的65%，固氮酶还原酶（nif H）的mRNA水平为MN - 110根瘤的64%。对来自相同根瘤的组织进行的Western印迹分析检测到，相对于MN - 110，L2 - 110中固氮酶水平为MN - 110的32%，固氮酶还原酶水平为MN - 110的31%。基于完全缺乏共生固氮能力（Fix -）和显著的体外固氮能力（Nif +），L2 - 110似乎是一类新的突变体。