Integrated transcriptome and metabolome analysis reveals the impacts of prolonged light exposure on starch and protein content in maize kernels.

Background: The light environment significantly influences crop growth, development, quality, and yield, particularly in controlled-environment agriculture. Recent advances in artificial lighting technology have allowed growers to precisely control the light environment in terms of duration, spectrum, and intensity. Starch and protein are the most significant nutritional constituents of maize kernels. However, little is known about the effects of the light environment on starch and protein content in maize kernels. Therefore, we investigated the effects of natural light and supplemental exposure to blue (B), far-red (FR), and red (R) light on starch and protein content in kernels of the inbred maize line B73.

Results: Exposure to supplemental B, FR, or R light resulted in significant increases in starch content but decreases in protein content. Notably, protein content was lowest under B light. Substantial proportions of genes (5.03-75.23%) and metabolites (46.89-85.64%) were regulated by different wavelengths of light. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, as well as weighted gene co-expression network analysis (WGCNA), revealed that differentially expressed genes (DEGs) under B, FR, and R light were involved in pathways related to starch and protein synthesis. KEGG metabolomic analysis showed that differentially abundant metabolites (DAMs) were primarily associated with histidine, D-amino acid, cysteine, and methionine metabolism. Nine DEGs related to starch synthesis were identified as potential candidates for investigating the effects of light quality on starch synthesis, and 14 DEGs related to protein synthesis provided evidence for the influence of light quality on protein synthesis in maize.

Conclusions: This study identified the regulatory network governing starch and protein content in B73 maize kernels under different light conditions, contributing to a deeper understanding of how light quality affects the nutritional components of maize kernels.