Phosphoglucose isomerase (PGI) catalyzes the reversible isomerization of fructose-6-phosphate and glucose-6-phosphate (G6P). It is involved in glycolysis and in the regeneration of G6P molecules in the oxidative pentose phosphate pathway (OPPP). The plastid-localized phosphoglucose isomerase (PGI) isoform, PGI1, is an important determinant of growth and photosynthesis in Arabidopsis likely as a consequence of its involvement in the synthesis of plastid-localized isoprenoids and derived compounds (Bahaji et al. 2015, PLoS ONE. DOI:10.1371/journal.pone.0119641; Sánchez-López et al. 2016, Plant Physiol. 172: 1989-2001). In this work we investigated the contribution made by PGI1 to seed yield and oil synthesis. Gene expression analyses showed that PGI1 is strongly expressed in vascular tissues of roots, leaves, cotyledons and shoots, and maturing seed embryos. The seed yield of PGI1-null pgi1-2 plants was only ca. 30% that of wild type (WT) plants. Silique number per plant in pgi1-2 was strongly reduced when compared with WT plants as a consequence of a diminution in the number of inflorescences, a phenotype that could be rescued by exogenous gibberellin (GA) application.pgi1-2 seeds showed reduced seed weight and accumulated only ca. 50% of the WT fatty acid (FA) content, causing a wrinkled seed phenotype that could be restored to WT by ectopic expression of PGI1. Moreover, pgi1-2 seedlings showed reduced frequency of establishment, which could be rescued by provision of exogenous sucrose. Seeds from crosses between pgi1-2 and WT plants accumulated WT levels of FA, strongly indicating that the low seed oil content phenotype of pgi1-2 is zigotically determined. OOur results provide evidence that PGI1 is an important determinant of Arabidopsis seed yield as a consequence of its involvement in two independent processes: theformation of inflorescences through GA action, and the metabolic conversion of plastidic glucose-6-phosphate into FA.

Trabajo presentado en la XXII Reunión de la Sociedad Española de Fisiología Vegetal / XV Spanish Portuguese Congress of Plant Physiology, celebrada en Barcelona (España), del 26 al 29 de junio de 2017

Peer reviewed