Analysis of global gene expression in vegetative and reproductive tissues of maize (Zea mays) that differ in accumulation of starch and sucrose

Background. Carbon allocation between vegetative and reproductive tissues impacts cereal grain production. Despite their great agricultural importance, sink-source relationships have not been fully characterized at early reproductive stages in maize. Here we quantify the accumulation of non-structural carbohydrates and patterns of gene expression in the top internode of the stem and the female inflorescence of maize at the onset of grain filling (reproductive stage R1). Methods. Top internode stem and female inflorescence tissues of the Puma maize inbred line were collected at reproductive stage R1 (without pollination). The accumulation of non-structural carbohydrates was quantified by spectrophotometry. Global gene expression was evaluated in both tissues by RNA sequencing. Results. At reproductive stage R1, the maize female inflorescence accumulates non-structural carbohydrates, notably starch, at higher levels than the top internode of the stem. Gene expression analysis identified 491 genes to be differentially expressed between the female inflorescence and the stem top internode. Gene ontology classification of differentially expressed genes showed enrichment for sucrose synthesis, the light-dependent reactions of photosynthesis, and transmembrane transporters. Our results suggest that sugar transporters play a key role in sugar partitioning in the maize stem and reveal previously uncharacterized differences between the female inflorescence and the top internode of the stem at early reproductive stages. RNA-seq of two maize tissues by duplicated, the female inflorescence and the top internode section of the stem at reproductive stage before pollination, with differentalstarch and sucrose level