A 2-bp frameshift deletion at GhDR, which encodes a B-BOX protein that co-segregates with the dwarf-red phenotype in Gossypium hirsutums L.

Plant architecture and leaf color are important factors influencing cotton fiber yield. In this study, based on genetic analysis, stem paraffin sectioning, and phytohormone treatments, we showed that the dwarf-red (DR) cotton mutant is a gibberellin-sensitive mutant caused by a mutation in a single dominant locus, designated GhDR. Using bulked segregant analysis (BSA) and genotyping by target sequencing (GBTS) approaches, we located the causative mutation to a ~197-kb genetic interval on chromosome A09 containing 25 annotated genes. Based on gene annotation and expression changes between the mutant and normal plants, GH_A09G2280 was considered to be the best candidate gene responsible for the dwarf and red mutant phenotypes. A 2-nucleotide deletion was found in the coding region of GhDR/GH_A09G2280 in the DR mutant, which caused a frameshift and truncation of GhDR. GhDR is a homolog of Arabidopsis AtBBX24, and encodes a B-box zinc finger protein. The frameshift deletion eliminated the C-terminal nuclear localization domain and the VP domain of GhDR, and altered its subcellular localization. A comparative transcriptome analysis demonstrated downregulation of the key genes involved in gibberellin biosynthesis and the signaling transduction network, as well as upregulation of the genes related to gibberellin degradation and the anthocyanin biosynthetic pathway in the DR mutant. The results of this study revealed the potential molecular basis by which plant architecture and anthocyanin accumulation are regulated in cotton.