The role of cytosolic glutamine synthetase in wheat

Abstract

SummaryThe role of glutamine synthetase (GS; EC 6.3.1.2) was studied in wheat. GS isoforms were separated by HPLC and the two major leaf isoforms (cytosolic GS1 and chloroplastic GS2) were found to change in content and activity throughout plant development. GS2 dominated activity in green, rapidly photosynthesising leaves compared to GS1 which was a minor component. GS2 remained the main isoform in flag leaves at the early stages of grain filling but GS1 activity increased as the leaves aged. During senescence, there was a decrease in total GS activity which resulted largely from the loss of GS2 and thus GS 1 became a greater contributor to total GS activity. The changes in the activities of the GS isoforms were mirrored by the changes in GS proteins measured by western blotting. The changes in GS during plant development reflect major transitions in metabolism from a photosynthetic leaf (high GS2 activity) towards a senescencing leaf (relatively high GS1 activity). It is likely that, during leaf maturation and subsequently senescence, GS1 is central for the efficient reassimilation of ammonium released from catabolic reactions when photosynthesis has declined and remobilisation of nitrogen is occurring. Preliminary analysis of transgenic wheat lines with increased GS1 activity in leaves showed that they develop an enhanced capacity to accumulate nitrogen in the plant, mainly in the grain, and this is accompanied by increases in root and grain dry matter. The possibility that the manipulation of GS may provide a means of enhancing nitrogen use in wheat is discussed.

Improving Nitrogen Use Efficiency in Crops for Sustainable Agriculture

“…In wheat, the overexpression of a gene for GS1 from French bean led to an increase in grain yield (grain weight in particular) and therefore of NUE, which was estimated to be about 20% [158]. However, to our knowledge there has been no further development of this interesting study, either because of the difficulty of field testing in Europe or because this testing is currently being performed in the private sector.…”

Improving Plant Nitrogen Use Efficiency through Alteration of Amino Acid Transport Processes

“…Nitrogen utilization efficiency (NUtE) is defined as total seed yield relative to total shoot N content (Moll et al, 1982) and is affected by several physiological factors, including N uptake, metabolism, allocation, and remobilization (Habash et al, 2001;Tsay et al, 2011;Girondé et al, 2015). In addition, regulated transport of N within the plant strongly influences the amount of N allocated to seeds and final seed yields (Rolletschek et al, 2005;Schmidt et al, 2007;Weigelt et al, 2008;Tan et al, 2010;Zhang et al, 2010Zhang et al, , 2015Carter and Tegeder, 2016;Santiago and Tegeder, 2016 Araus et al, 2016;Chen et al, 2017), nitrate allocation (Tsay et al, 2011), N metabolism (Ameziane et al, 2000Chichkova et al, 2001;Habash et al, 2001;Yamaya et al, 2002;Seiffert et al, 2004;Good et al, 2007;Shrawat et al, 2008;Peña et al, 2017), and its regulation (Yanagisawa et al, 2004). While generally successful, these studies often did not address the different components of NUE (i.e.…”

Superexpressão do transportador OsNPF4.11 (OsNRT1.2) afeta teor de nitrato, parâmetros radiculares e crescimento de arroz

“…Tendo em vista que a enzima Nitrato Redutase (NR) é citosólica, a redução do nitrato é principalmente realizada no citoplasma, desta forma o NO 3 -acumulado no vacúolo precisa ser remobilizado para o citoplasma para ser então assimilado e reduzido, assim a EUN em plantas está intimamente relacionada com a capacidade de reutilização do NO 3 -do vacúolo (Zhang et al, 2012). Por meio do estudo de plantas transgênicas, já foi demonstrado que uma redução na assimilação do N acarretou em uma redução na biomassa em plantas de arroz (Kusano et al, 2011) e que um aumento na assimilação acarretou em um aumento na biomassa das plantas, assim como um aumento na massa seca de raiz e de parte aérea em plantas de trigo e tabaco (Migge et al, 2000;Fuentes et al, 2001;Habash et al, 2001).…”