scholarly journals Aspartate Aminotransferase in Alfalfa Root Nodules

1990 ◽  
Vol 93 (2) ◽  
pp. 603-610 ◽  
Author(s):  
Mark W. Farnham ◽  
Susan S. Miller ◽  
Stephen M. Griffith ◽  
Carroll P. Vance
Keyword(s):  
Aspartate Aminotransferase ◽  
Root Nodules ◽  
Alfalfa Root

scholarly journals Aspartate Aminotransferase in Alfalfa Root Nodules

1990 ◽  
Vol 94 (4) ◽  
pp. 1634-1640 ◽  
Author(s):  
Mark W. Farnham ◽  
Stephen M. Griffith ◽  
Susan S. Miller ◽  
Carroll P. Vance
Keyword(s):  
Aspartate Aminotransferase ◽  
Root Nodules ◽  
Alfalfa Root

scholarly journals Aspartate Aminotransferase in Alfalfa Root Nodules

1989 ◽  
Vol 90 (4) ◽  
pp. 1622-1629 ◽  
Author(s):  
Stephen M. Griffith ◽  
Carroll P. Vance
Keyword(s):  
Aspartate Aminotransferase ◽  
Root Nodules ◽  
Alfalfa Root

Reactive oxygen species accumulation patterns of alfalfa root nodules identified using an optimized method

2019 ◽  
Vol 51 (4) ◽  
pp. 448-451
Author(s):  
Liangliang Yu ◽  
Leqi Huang ◽  
Shuang Zeng ◽  
Guirong Tang ◽  
Sunjun Wang ◽  
...  
Keyword(s):  
Reactive Oxygen Species ◽  
Root Nodules ◽  
Reactive Oxygen ◽  
Oxygen Species ◽  
Reactive Oxygen Species Accumulation ◽  
Species Accumulation ◽  
Alfalfa Root

scholarly journals Malic Enzyme Cofactor and Domain Requirements for Symbiotic N2 Fixation by Sinorhizobium meliloti

2006 ◽  
Vol 189 (1) ◽  
pp. 160-168 ◽  
Author(s):  
Michael J. Mitsch ◽  
Alison Cowie ◽  
Turlough M. Finan
Keyword(s):  
Amino Acid ◽  
Malic Enzyme ◽  
Sinorhizobium Meliloti ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
High Ratio ◽  
Terminal Region ◽  
Wild Type ◽  
Mutant Strains ◽  
Alfalfa Root

ABSTRACT The NAD+-dependent malic enzyme (DME) and the NADP+-dependent malic enzyme (TME) of Sinorhizobium meliloti are representatives of a distinct class of malic enzymes that contain a 440-amino-acid N-terminal region homologous to other malic enzymes and a 330-amino-acid C-terminal region with similarity to phosphotransacetylase enzymes (PTA). We have shown previously that dme mutants of S. meliloti fail to fix N2 (Fix−) in alfalfa root nodules, whereas tme mutants are unimpaired in their N2-fixing ability (Fix+). Here we report that the amount of DME protein in bacteroids is 10 times greater than that of TME. We therefore investigated whether increased TME activity in nodules would allow TME to function in place of DME. The tme gene was placed under the control of the dme promoter, and despite elevated levels of TME within bacteroids, no symbiotic nitrogen fixation occurred in dme mutant strains. Conversely, expression of dme from the tme promoter resulted in a large reduction in DME activity and symbiotic N2 fixation. Hence, TME cannot replace the symbiotic requirement for DME. In further experiments we investigated the DME PTA-like domain and showed that it is not required for N2 fixation. Thus, expression of a DME C-terminal deletion derivative or the Escherichia coli NAD+-dependent malic enzyme (sfcA), both of which lack the PTA-like region, restored wild-type N2 fixation to a dme mutant. Our results have defined the symbiotic requirements for malic enzyme and raise the possibility that a constant high ratio of NADPH + H+ to NADP in nitrogen-fixing bacteroids prevents TME from functioning in N2-fixing bacteroids.

scholarly journals Aspartate Aminotransferase in Alfalfa Nodules: Localization of mRNA During Effective and Ineffective Nodule Development and Promoter Analysis

1999 ◽  
Vol 12 (4) ◽  
pp. 263-274 ◽  
Author(s):  
Hirofumi Yoshioka ◽  
Robert G. Gregerson ◽  
Deborah A. Samac ◽  
Kim C. M. Hoevens ◽  
Gian Trepp ◽  
...  
Keyword(s):  
Aspartate Aminotransferase ◽  
Root Nodules ◽  
Critical Role ◽  
Nodule Development ◽  
Vascular Bundles ◽  
Fixed Nitrogen ◽  
Transcript Accumulation ◽  
Specific Expression ◽  
Promoter Deletion Analysis

Aspartate aminotransferase (AAT) plays a critical role in the assimilation of symbiotically fixed nitrogen into aspartate and asparagine in legume root nodules. The enzyme occurs as a cytosolic form (AAT1) and a plastid form (AAT2) in alfalfa nodules. To elucidate the functional role of each isozyme in root nodule metabolism further, in situ hybridization was used to determine the pattern of transcript accumulation from the two genes. AAT2 transcripts were localized to infected cells throughout the symbiotic zone of effective alfalfa nodules; however, expression was reduced in ineffective nodules. The AAT1 gene was expressed in the uninfected cells of the invasion zone and symbiotic zone, the nodule parenchyma, and nodule vascular bundles of both effective and ineffective nodules. The AAT1 and AAT2 promoters were evaluated in transgenic alfalfa plants containing promoter β-glucuronidase (GUS) gene fusions. Histochemical staining patterns agreed with results from in situ localization. The distribution pattern of gene transcripts suggests that AAT1 has a role in maintenance of the O2 diffusion barrier in nodules and that AAT2 plays a major role in assimilation of recently fixed nitrogen. Promoter deletion analysis of the AAT2 promoter revealed that nodule-specific expression was retained in a promoter fragment of 300 bp.

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