A DEAD-box RNA helicase encoded by DEK223 is essential for maize kernel development by affecting pre-rRNA processing.

The ribosomes play a crucial role in gene expression across all organisms. In eukaryotes, the 80S monosome consists of the 40S small subunit and the 60S large subunit. Ribosome biogenesis is a meticulously coordinated process that encompasses multiple ribosome biogenesis factors. Despite the significant advancements achieved in yeast research, the precise role of ribosome biogenesis factors in pre-ribosomal RNA (pre-rRNA) processing and plant development remains largely unclear. Here, we isolated a maize Mutator transposon insertion defective kernel (dek) mutant, designated dek223. Map-based cloning revealed that DEK223 encodes a DEAD-box RNA helicase with 57.46 % identity to yeast HAS1. DEK223 is localized in the nucleolus and is constitutively expressed across most of the major tissues. Ribosome profiling and RNA gel blotting demonstrated that mutation of DEK223 impairs ribosome biogenesis and pre-rRNA processing, accompanied by reduction in 40S subunit synthesis and the delayed processing of multiple pre-rRNA intermediates. DEK223 physically interacts with two A factors, ZmNop15 and ZmRlp7, which are reported to be required for 60S subunit biogenesis and the recruitment of HAS1 to pre-ribosomes in yeast. Overall, the results underscore the crucial involvement of DEK223 in the biogenesis of the ribosome 40S subunits and the processing of multiple pre-rRNAs, both essential for embryogenesis during maize kernel development.