DPE1, a novel allelic of BT1, is critical for maize endosperm development and carbohydrate metabolism

Maize (Zea mays) endosperm is the primary tissue for storing nutrients, such as starch, that provide the developing embryo with energy. Endosperm mutants are useful for clarifying carbohydrate synthesis and metabolism as well as the molecular mechanism underlying endosperm development in maize. In this study, we identified a novel maize mutant exhibiting abnormal endosperm development. This mutant, which was named dysplastic endosperm1 (dpe1), contained a shrunken, collapsed, and opaque endosperm. Using a map-based cloning strategy, DPE1 was identified as Zm00001d015746. Moreover, an allelism test confirmed that DPE1 is allelic to the previously reported gene ZmBT1. The dpe1 mutant phenotype was revealed to be due to a single-nucleotide substitution that results in the substitution of a single amino acid. DPE1, which was highly expressed in kernels, was predicted to encode an ADP-glucose transporter localized in the chloroplast. Analyses of phylogenetic relationships and functional evolution suggested that this ADP-glucose transporter may have distinct functions in monocotyledons and dicotyledons. Transcriptome analyses and quantitative detection of small-molecule carbohydrate compounds indicated that differentially expressed genes and differentially abundant metabolites were significantly associated with carbohydrate metabolism-related pathways, implying that loss-of-function mutations to DPE1 lead to inhibited carbohydrate synthesis and transport. Thus, our study provides insights into the molecular basis of maize kernel endosperm development as well as genetic resources for the molecular breeding of maize.