Identification of a UDP-glucuronosyl/UDP-glucosyltransferase involved in rice seedling height regulation

Seedling height is an important agronomic trait for early vigor and crop establishment in rice. It is controlled by multiple genes, as shown by the continuous variation and normal distribution observed in the Cheongcheong × Nagdong double haploid population measured from 6 to 24 days after sowing. This study identified 32 quantitative trait loci QTLs associated with seedling height across multiple chromosomes. Subsequent candidate gene analysis within overlapping QTL regions identified 44 genes associated with growth, metabolism, and stress responses. A key finding was the identification of Os06g0282000 on chromosome 6 between RM540 and RM586, which encodes a putative UDP-glucuronosyl/UDP-glucosyltransferase (UGT). This gene showed consistently higher expression in tall CNDH lines and increased expression during the 12-24 DAS period, indicating a positive correlation with seedling growth. Gene Ontology enrichment showed the role of QTL-associated genes in hormone signaling and carbohydrate metabolism, emphasizing their roles in early seedling development. Comparative genomic analysis showed that Os06g0282000 is part of a conserved gene family that includes 51 homologous genes in rice. Phylogenetic analysis supported its close relationship with UGTs involved in regulating plant growth. These findings position Os06g0282000 as a strong candidate gene that may play a key role in seedling height QTLs and emphasize the role of UGT-mediated regulation of phytohormone homeostasis in controlling rice seedling growth and development.