Proteomics Analysis Reveals Hormone Metabolic Process Involved in the Regulation of Kernel Water Content Induced by Exogenous Abscisic Acid in Maize

The water content of maize kernels during harvest is a critical factor influencing grain harvest practices globally. Abscisic acid (ABA) plays a pivotal role in grain development during the grain-filling process. Yet, there has been limited reporting on the regulatory mechanism of grain dehydration induced by exogenous ABA using proteomic techniques. In this study, two maize genotypes with distinct dehydration rates, DK517 (fast dehydration) and ZD1002 (slow dehydration), were treated with ABA after the heading stage. Results revealed a 20% lower yield in DK517 compared to ZD1002 following ABA application. Sixty days after pollination, the grain water content decreased to 23.55% in DK517 and 30.42% in ZD1002 due to ABA treatment. Through proteomic analysis, 861 and 118 differentially expressed proteins (DAPs) were identified in DK517 and ZD1002, respectively, as a result of ABA treatment. GO analysis indicated that the primary metabolic process, nitrogen compound metabolic process, and hormone metabolic process were significantly enriched among the DAPs in DK517 induced by ABA, while these pathways were absent in ZD1002. Twenty-four and fifteen overlapping DAPs showed contrasting responses in the two maize genotypes after ABA treatment. Notably, the expression levels of six known ABA signaling genes, including SnRK2 and DRE-like proteins, were downregulated in DK517 but remained unaltered in ZD1002 following ABA application. These findings underscore the distinct effects of exogenous ABA on the grain-filling characteristics of different maize genotypes, emphasizing the importance of the hormone metabolic process in regulating kernel water content induced by exogenous abscisic acid in maize.