Disruption of pseudouridine kinase OsPUKI impairs grain yield and quality in rice

Yield and quality are two core objectives in rice breeding. PfkB protein plays a significant role in plant growth and development. OsPUKI, the only pseudouridine kinase subfamily member in rice, belonging to the PfkB family, but its roles in grain weight and quality remain poorly characterized. Here, we found that OsPUKI was predominantly expressed in the stem, panicle, leaf sheath, embryo, and germ of sprouting seeds. Knockout of OsPUKI significantly decreased grain yield per plant by 35.97-51.66% and thousand grain weight by 3.37-6.20%, accompanied by reduced grain width and thickness. Cytological analysis revealed a marked reduction in the cell width of spikelet hull in the ospuki lines. We further observed a decrease in starch and total lipid content, along with altered starch gelatinization properties in these mutants. In contrast, the contents of seed storage proteins, Asp, Glu, Tyr, Leu, Val and Phe were found to be elevated. The transcription level of starch synthesis-related genes (OsGBSS1, OsAGPL2, OsPFP1β, OsSSI, OsSSIIc and OsSSIIIb) was significantly decreased in the ospuki lines. Additionally, the expression of genes associated with protein and amino acid metabolism (Pro14, RM1, OsGluA2, LOC_Os02g41650 and LOC_Os01g65090) undergoes significant changes. Collectively, these findings indicate that OsPUKI may play critical roles in regulating grain size and weight by influencing spikelet hull cell proliferation and expansion, as well as the accumulation of storage substances, thereby affecting both rice yield and grain quality.