Regulation of Zn and Fe transporters by the GPC1gene during early wheat monocarpic senescence

Background; During wheat senescence, leaf components are degraded in a coordinated manner, releasing amino acids and micronutrients which are subsequently transported to the developing grain. We have previously shown that the simultaneous downregulation of Grain Protein Content (GPC) transcription factors, GPC1 and GPC2, greatly delays senescence and disrupts nutrient remobilization, and therefore provide a valuable entry point to identify genes involved in micronutrient transport to the wheat grain. Results: We generated loss-of-function mutations for GPC1 and GPC2 in tetraploid wheat and showed in field trials that gpc1 mutants exhibit significant delays in senescence and reductions in grain Zn and Fe content, but that mutations in GPC2 had no significant effect on these traits. An RNA-seq study of these mutants at different time points showed a larger proportion of senescence-regulated genes among the GPC1 (64%) than among the GPC2 (37%) regulated genes. Combined, the two GPC genes regulate a subset (21.2%) of the senescence-regulated genes, 76.1% of which are upregulated at 12 days after anthesis, before the appearance of any visible signs of senescence. Taken together, these results demonstrate that GPC1 is a key regulator of nutrient remobilization which acts predominantly during the early stages of senescence. Genes upregulated at this stage include transporters from the ZIP and YSL gene families, which facilitate Zn and Fe export from the cytoplasm to the phloem, and genes involved in the biosynthesis of chelators that facilitate the phloem-based transport of these nutrients to the grains. Conclusions: This study provides an overview of the transport mechanisms activated in the wheat flag leaf during monocarpic senescence. It also identifies promising targets to improve nutrient remobilization to the wheat grain, which can help mitigate Zn and Fe deficiencies that afflict many regions of the developing world.

Instituto de Recursos Biológicos

Fil: Pearce, Stephen. University of California. Department of Plant Sciences; Estados Unidos

Fil: Tabbita, Facundo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Recursos Biológicos; Argentina

Fil: Cantu, Dario. University of California. Department of Viticulture and Enology; Estados Unidos

Fil: Buffalo, Vince. University of California. Department of Plant Sciences; Estados Unidos

Fil: Avni, Raz. Tel Aviv University. Faculty of Life Sciences. Department of Molecular Biology and Ecology of Plants; Israel

Fil: Vazquez Gross, Hans. University of California. Department of Plant Sciences; Estados Unidos

Fil: Zhao, Rongrong. China Agricultural University. College of Resources and Environmental Science. Department of Plant Nutrition; China

Fil: Conley, Christopher J. University of California. Department of Statistics; Estados Unidos

Fil: Distelfeld, Assaf. Tel Aviv University. Faculty of Life Sciences. Department of Molecular Biology and Ecology of Plants; Israel

Fil: Dubcovsky, Jorge. University of California. Department of Plant Sciences; Estados Unidos. Howard Hughes Medical Institute; Estados Unidos