GhHB12 negatively regulates abiotic stress tolerance in Arabidopsis and cotton

•The overexpression of GhHB12 in cotton and Arabidopsis resulted in a decreased sensitiveness to ABA and decreased salt/drought tolerance by suppressing the expression of ABA-responsive genes and stress-related genes (ABI2, DREB2A, RD29A, RD22, RD26, RD28, SOS1, SOS2, NHX1 and HKT1). Down-expression of GhHB12 increases the tolerance to abiotic stress in cotton.•GhHB12 cooperated with other transcription factors, kinases, and enzymes to regulate plant development and abiotic stress tolerance.•There was an expansion of GhHB12 homologous genes in G. hirsutum, and the homoeologous gene pairs showed biased A-subgenome or d-subgenome expression.