Functional characterization of GPC-1 genes in hexaploid wheat.

Raz Avni, Rongrong Zhao, Stephen Pearce, Yan Jun, Cristobal Uauy, Facundo Tabbita, Tzion Fahima, Ann Slade, Jorge Dubcovsky, Assaf Distelfeld

Planta 2014 Feb

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In wheat, monocarpic senescence is a tightly regulated process during which nitrogen (N) and micronutrients stored pre-anthesis are remobilized from vegetative tissues to the developing grains. Recently, a close connection between senescence and remobilization was shown through the map-based cloning of the GPC (grain protein content) gene in wheat. GPC-B1 encodes a NAC transcription factor associated with earlier senescence and increased grain protein, iron and zinc content, and is deleted or non-functional in most commercial wheat varieties. In the current research, we identified 'loss of function' ethyl methanesulfonate mutants for the two GPC-B1 homoeologous genes; GPC-A1 and GPC-D1, in a hexaploid wheat mutant population. The single gpc-a1 and gpc-d1 mutants, the double gpc-1 mutant and control lines were grown under field conditions at four locations and were characterized for senescence, GPC, micronutrients and yield parameters. Our results show a significant delay in senescence in both the gpc-a1 and gpc-d1 single mutants and an even stronger effect in the gpc-1 double mutant in all the environments tested in this study. The accumulation of total N in the developing grains showed a similar increase in the control and gpc-1 plants until 25 days after anthesis (DAA) but at 41 and 60 DAA the control plants had higher grain N content than the gpc-1 mutants. At maturity, GPC in all mutants was significantly lower than in control plants while grain weight was unaffected. These results demonstrate that the GPC-A1 and GPC-D1 genes have a redundant function and play a major role in the regulation of monocarpic senescence and nutrient remobilization in wheat.

Citation

Raz Avni, Rongrong Zhao, Stephen Pearce, Yan Jun, Cristobal Uauy, Facundo Tabbita, Tzion Fahima, Ann Slade, Jorge Dubcovsky, Assaf Distelfeld. Functional characterization of GPC-1 genes in hexaploid wheat. Planta. 2014 Feb;239(2):313-324