Ascorbic acid synthesis and metabolism in maize are subject to complex and genotype-dependent feedback regulation duringendosperm development

Abstract

L-ascorbic acid (vitamin C) is an antioxidant and electron donor whose metabolism in plants isunder strict feedback control. The factors that influence L-ascorbic acid accumulation in staplecrops are only partially understood. One way to gain insight into the regulation of L-ascorbic acidmetabolism is to investigate the endogenous pathways in various genetic backgrounds and char-acterize their interactions with transgenes encoding relevant enzymes. In an initial step, we inves-tigated the developmental profile of L-ascorbic acid accumulation in the endosperm of threediverse maize genotypes and a transgenic line expressing rice dehydroascorbate reductase, whichenhances L-ascorbic acid recycling. We determined the transcript levels of all the key genes in theL-ascorbic acid metabolic pathways as well as the specific levels of ascorbic acid and dehy-droascorbate. L-ascorbic acid levels were high 20 days after pollination and declined thereafter. Wefound significant genotype-dependent variations in the transcript levels of some genes, with par-ticular complexity in the ascorbic acid recycling pathway. Our data will help to elucidate the com-plex mechanisms underlying the regulation of L-ascorbic acid metabolism in plants, particularlythe impact of genetic background on the strict regulation of ascorbic acid metabolism inendosperm cells.

This study was supported by the Ministerio de Ciencia e Innovación, Spain (BIO2007-61413 and BIO2011-22525),Proyecto Consolider-Ingenio 2010 Centre Agrigenomica CSD2007-00036, RecerCaixa, and European ResearchCouncil Advanced Grant (BIOFORCE) to PC.