The glutamine synthetase gene family in Populus.

Vanessa Castro-Rodríguez,Javier Canales,Edward G Kirby,Concepción Avila,Angel García-Gutiérrez,Francisco M Cánovas

doi:10.1186/1471-2229-11-119

Vanessa Castro-Rodríguez, Javier Canales + Show 4 more

Open Access

https://doi.org/10.1186/1471-2229-11-119

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Abstract

BackgroundGlutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) is a key enzyme in ammonium assimilation and metabolism of higher plants. The current work was undertaken to develop a more comprehensive understanding of molecular and biochemical features of GS gene family in poplar, and to characterize the developmental regulation of GS expression in various tissues and at various times during the poplar perennial growth.ResultsThe GS gene family consists of 8 different genes exhibiting all structural and regulatory elements consistent with their roles as functional genes. Our results indicate that the family members are organized in 4 groups of duplicated genes, 3 of which code for cytosolic GS isoforms (GS1) and 1 which codes for the choroplastic GS isoform (GS2). Our analysis shows that Populus trichocarpa is the first plant species in which it was observed the complete GS family duplicated. Detailed expression analyses have revealed specific spatial and seasonal patterns of GS expression in poplar. These data provide insights into the metabolic function of GS isoforms in poplar and pave the way for future functional studies.ConclusionsOur data suggest that GS duplicates could have been retained in order to increase the amount of enzyme in a particular cell type. This possibility could contribute to the homeostasis of nitrogen metabolism in functions associated to changes in glutamine-derived metabolic products. The presence of duplicated GS genes in poplar could also contribute to diversification of the enzymatic properties for a particular GS isoform through the assembly of GS polypeptides into homo oligomeric and/or hetero oligomeric holoenzymes in specific cell types.

Highlights

Glutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) is a key enzyme in ammonium assimilation and metabolism of higher plants
The full-length cDNAs (FLcDNAs) of the 8 GS genes were analyzed and the characteristics of the polypeptides encoded by their open reading frames (ORFs) were compared (Table 1)
Our analysis suggests that the GS gene family in poplar is organized in 4 groups of duplicated genes, PtGS1.1, PtGS1.2, PtGS1.3 and PtGS2

Summary

Introduction

Glutamine synthetase (GS; EC: 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) is a key enzyme in ammonium assimilation and metabolism of higher plants. Glutamine synthetase (GS; EC 6.3.1.2, L-glutamate: ammonia ligase ADP-forming) catalyzes the ATP-dependent addition of ammonium (NH4+) to the g-carboxyl group of glutamate to produce glutamine and acts as the center for nitrogen flow in plants. The ammonium assimilated by GS in the production of glutamine can come from various sources, including direct uptake from the soil, reduction of nitrate and nitrite, photorespiration, deamination of phenylalanine catalyzed by Multiple nuclear encoded GS polypeptides are expressed in photosynthetic and non-photosynthetic tissues of higher plants and these polypeptides are assembled into oligomeric isoenzymes located either in the cytosol or in the chloroplast [2,3]. Molecular analysis of genomic GS sequences from a number of angiosperm species has shown that the cytosolic GS1 genes belong to a small multigene family, whereas, the chloroplastic GS2 is encoded by a single gene [9,10]

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