NAD(P)+-Malic Enzyme Mutants of Sinorhizobium sp. Strain NGR234, but Not Azorhizobium caulinodans ORS571, Maintain Symbiotic N2 Fixation Capabilities
NAD(P)+-Malic Enzyme Mutants of Sinorhizobium sp. Strain NGR234, but Not Azorhizobium caulinodans ORS571, Maintain Symbiotic N2 Fixation Capabilities
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NAD(P)-中华根瘤菌的苹果酸酶突变体。
DOI：
10.1128/aem.06412-11
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发表时间：
2012
影响因子：
4.4
通讯作者：
T. Finan
中科院分区：
文献类型：
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作者：
Ye Zhang;T. Aono;P. Poole;T. Finan
摘要豆科植物根瘤中的固氮菌（类杆菌）似乎通过三羧酸（TCA）循环代谢C4-二羧酸。在苜蓿中华根瘤菌类菌体中，NAD+-苹果酸酶（DME）是固氮所必需的，并且这种活性被认为是丙酮酸回补合成所必需的。与此相反，在豌豆共生根瘤菌，丙酮酸合成发生通过DME或磷酸烯醇丙酮酸羧激酶（PCK）和丙酮酸激酶（PYK）催化的途径。在这里，我们报告的dme突变体的广泛的主机范围中华根瘤菌属。菌株NGR 234形成的结节，其固氮水平从27%至83%（植物干重）的野生型水平，这取决于宿主植物接种。NGR 234类杆菌具有显著的PCK活性，而单个pckA和单个dme突变体以降低的速率固定N2，pckA dme双突变体没有N2固定活性（Fix−）。因此，NGR 234拟杆菌似乎通过DME或PCK途径从TCA循环中间体合成丙酮酸。这些NGR 234数据以及其他报告表明，S.苜蓿dme突变体可能是苜蓿-S.苜蓿共生因此，我们研究了来自Azorhizobium caulinodans的ME样基因azc 3656和azc 0119，因为azc 3656突变体以前被证明可以在热带豆科植物田菁上形成Fix-结节。我们发现纯化的AZC 3656蛋白是一种NAD（P）+-苹果酸酶，其活性被乙酰辅酶A（acetyl-CoA）抑制，并被琥珀酸和延胡索酸激活。因此，虽然DME是A. caulinodans和S.在苜蓿根瘤菌中，这种活性可以通过另一种途径绕过。
ABSTRACT C4-dicarboxylic acids appear to be metabolized via the tricarboxylic acid (TCA) cycle in N2-fixing bacteria (bacteroids) within legume nodules. In Sinorhizobium meliloti bacteroids from alfalfa, NAD+-malic enzyme (DME) is required for N2 fixation, and this activity is thought to be required for the anaplerotic synthesis of pyruvate. In contrast, in the pea symbiont Rhizobium leguminosarum, pyruvate synthesis occurs via either DME or a pathway catalyzed by phosphoenolpyruvate carboxykinase (PCK) and pyruvate kinase (PYK). Here we report that dme mutants of the broad-host-range Sinorhizobium sp. strain NGR234 formed nodules whose level of N2 fixation varied from 27 to 83% (plant dry weight) of the wild-type level, depending on the host plant inoculated. NGR234 bacteroids had significant PCK activity, and while single pckA and single dme mutants fixed N2 at reduced rates, a pckA dme double mutant had no N2-fixing activity (Fix−). Thus, NGR234 bacteroids appear to synthesize pyruvate from TCA cycle intermediates via DME or PCK pathways. These NGR234 data, together with other reports, suggested that the completely Fix− phenotype of S. meliloti dme mutants may be specific to the alfalfa-S. meliloti symbiosis. We therefore examined the ME-like genes azc3656 and azc0119 from Azorhizobium caulinodans, as azc3656 mutants were previously shown to form Fix− nodules on the tropical legume Sesbania rostrata. We found that purified AZC3656 protein is an NAD(P)+-malic enzyme whose activity is inhibited by acetyl-coenzyme A (acetyl-CoA) and stimulated by succinate and fumarate. Thus, whereas DME is required for symbiotic N2 fixation in A. caulinodans and S. meliloti, in other rhizobia this activity can be bypassed via another pathway(s).
DOI：
10.1073/pnas.120163297
发表时间：
2000-06-06
影响因子：
11.1
作者：
Datsenko, KA;Wanner, BL
通讯作者：
Wanner, BL
NAD-苹果酸酶，而不是 NADP-苹果酸酶，影响根瘤中中索根瘤菌类菌的固氮酶活性
DOI：
--
发表时间：
2010
期刊：
Plant Biotech
影响因子：
--
作者：
Nanthipak Thapanapongworakul;Mika Nomura;Yoshikazu Shimoda;Shusei Sato;Satoshi Tabata and Shigeyuki Tajima
通讯作者：
Satoshi Tabata and Shigeyuki Tajima
影响因子：
14.9
作者：
Marchler-Bauer A;Lu S;Anderson JB;Chitsaz F;Derbyshire MK;DeWeese-Scott C;Fong JH;Geer LY;Geer RC;Gonzales NR;Gwadz M;Hurwitz DI;Jackson JD;Ke Z;Lanczycki CJ;Lu F;Marchler GH;Mullokandov M;Omelchenko MV;Robertson CL;Song JS;Thanki N;Yamashita RA;Zhang D;Zhang N;Zheng C;Bryant SH
通讯作者：
Bryant SH