NADH-glutamate synthase in alfalfa root nodules. Genetic regulation and cellular expression

Gian B. Trepp, Martijn V. Van De Mortel, Hirofumi Yoshioka, Susan S. Miller, Deborah A Samac, Steve Gantt, Carroll P. Vance

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

NADH-dependent glutamate synthase (NADH-GOGAT; EC 1.4.1.14) is a key enzyme in primary nitrogen assimilation in alfalfa (Medicago sativa L.) root nodules. Here we report that in alfalfa, a single gene, probably with multiple alleles, encodes for NADH-GOGAT. In situ hybridizations were performed to assess the location of NADH-GOGAT transcript in alfalfa root nodules. In wild-type cv Saranac nodules the NADH-GOGAT gene is predominantly expressed in infected cells. Nodules devoid of bacteroids (empty) induced by Sinorhizobium meliloti 7154 had no NADH-GOGAT transcript detectable by in situ hybridization, suggesting that the presence of the bacteroid may be important for NADH-GOGAT expression. The pattern of expression of NADH-GOGAT shifted during root nodule development. Until d 9 after planting, all infected cells appeared to express NADH-GOGAT. By d 19, a gradient of expression from high in the early symbiotic zone to low in the late symbiotic zone was observed. In 33-d-old nodules expression was seen in only a few cell layers in the early symbiotic zone. This pattern of expression was also observed for the nifH transcript but not for leghemoglobin. The promoter of NADH-GOGAT was evaluated in transgenic alfalfa plants carrying chimeric β-glucuronidase promoter fusions. The results suggest that there are at least four regulatory elements. The region responsible for expression in the infected cell zone contains an 88-bp direct repeat.

Original languageEnglish (US)
Pages (from-to)817-828
Number of pages12
JournalPlant physiology
Volume119
Issue number3
DOIs
StatePublished - Mar 1999

Fingerprint Dive into the research topics of 'NADH-glutamate synthase in alfalfa root nodules. Genetic regulation and cellular expression'. Together they form a unique fingerprint.

Cite this