Responses to Hypoxia and Endoplasmic Reticulum Stress Discriminate the Development of Vitreous and Floury Endosperms of Conventional Maize (Zea mays) Inbred Lines

Mathieu Gayral (1) , Khalil Elmorjani (1) , Michèle Dalgalarrondo (1) , Sandrine Balzergue (2, 3) , Stephanie Pateyron (3) , Marie Helene Morel (4) , Sylvie Brunet (5) , Laurent Linossier (5) , Caroline Delluc (6) , Benedicte Bakan (1) , Didier Marion (1)

1 BIA - Unité de recherche sur les Biopolymères, Interactions Assemblages
2 IRHS - Institut de Recherche en Horticulture et Semences
3 IPS2 (UMR_9213 / UMR_1403) - Institut des Sciences des Plantes de Paris-Saclay
4 UMR IATE - Ingénierie des Agro-polymères et Technologies Émergentes
5 Limagrain Cereales Ingredients
6 Groupe Limagrain

Major nutritional and agronomical issues relating to maize (Zea mays) grains depend on the vitreousness/hardness of its endosperm. To identify the corresponding molecular and cellular mechanisms, most studies have been conducted on opaque/floury mutants, and recently on Quality Protein Maize, are version of an opaque2 mutation by modifier genes. These mutant lines are far from conventional maize crops. Therefore, a dent and a flint inbred line were chosen for analysis of the transcriptome, amino acid, and sugar metabolites of developing central and peripheral endosperm that is, the forth coming floury and vitreous regions of mature seeds, respectively. The results suggested that the formation of endosperm vitreousness is clearly associated with significant differences in the responses of the endosperm to hypoxia and endoplasmic reticulum stress. This occurs through a coordinated regulation of energy metabolism and storage protein (i.e., zein) biosynthesis during the grain-filling period. Indeed, genes involved in the glycolysis and tricarboxylic acid cycle are up-regulated in the periphery, while genes involved in alanine, sorbitol, and fermentative metabolisms are up-regulated in the endosperm center. This spatial metabolic regulation allows the production of ATP needed for the significant zein synthesis that occurs at the endosperm periphery; this finding agrees with the zein-decreasing gradient previously observed from the sub-aleurone layer to the endosperm center. The massive synthesis of proteins transiting through endoplasmic reticulum elicits the unfolded protein responses, as indicated by the splicing of bZip60 transcription factor. This splicing is relatively higher at the center of the endosperm than at its periphery. The biological responses associated with this developmental stress, which control the starch/protein balance, leading ultimately to the formation of the vitreous and floury regions of mature endosperm, are discussed.

Mots clés: maize; endosperm; vitreousness; hypoxia; unfolded protein response (UPR); seed albumins; ergastoplasm; indian corn

Mots clés: vitrosite; endosperme; grain de maïs; transcriptome; réticulum endoplasmique; zea mays; hypoxie

Domaines: Biologie végétale

Mathieu Gayral, Khalil Elmorjani, Michèle Dalgalarrondo, Sandrine Balzergue, Stephanie Pateyron, et al.. Responses to Hypoxia and Endoplasmic Reticulum Stress Discriminate the Development of Vitreous and Floury Endosperms of Conventional Maize (Zea mays) Inbred Lines. Frontiers in Plant Science, 2017, 8, pp.557. ⟨10.3389/fpls.2017.00557⟩. ⟨hal-01602776⟩