Characterization and genetic mapping of dek1648 mutant reveals a DEAD-box RNA helicase involved in maize Kernel...

Kernel development is a critical determinant of maize yield and grain quality. This study investigated the defective kernel mutant dek1648 obtained through radiation mutagenesis, conducting comprehensive phenotypic characterization, genetic analysis, and molecular mapping. Phenotypic evaluation revealed severe developmental impairments in both embryo and endosperm, with mutant kernels exhibiting shriveled morphology, reduced size (12 % of wild-type weight). Genetic segregation analysis demonstrated that the mutant phenotype is controlled by a single recessive nuclear gene. Using an F₂ mapping population, we initially localized the mutation to chromosome 5 and subsequently narrowed the critical region to a 48.10-kb physical interval between markers ID0423 and ID0433. Candidate gene analysis identified a DEAD-box RNA helicase within this interval showing differential expression patterns and sequence variation in dek1648 (A critical 8-bp deletion in the CAMTA-binding motif from the positions -196 to -189 upstream of the Dek1648 start coden). Subcellular localization confirmed the nuclear targeting of this helicase. Functional characterization suggested its potential involvement in pri-miRNA processing through interaction with HYL protein, a core component of miRNA biogenesis pathways. Corresponding miRNA expression profiling revealed developmental stage-specific alterations, providing mechanistic insights into the kernel defects. These findings establish novel connections between RNA helicase-mediated miRNA regulation and cereal grain development.