The cotton transcription factor YP positively regulates petal size by enhancing brassinosteroid-dependent cell expansion.

The cotton transcription factor GhYP enhances petal size by promoting brassinosteroid biosynthesis and epidermal cell expansion, with petal size reduced by 06:00 on 0 DPA in mutants.

• Why it matters: Petal size influences ornamental appeal and reproductive success in flowering plants, yet the molecular mechanisms underlying its variation in non-model species like cotton are not well understood.
• What they did: Researchers identified the rapid petal elongation phase from -1 DPA to 0 DPA, disrupted GhYP gene function in cotton, and performed transcriptome and metabolome profiling, along with exogenous BR application and gene assays.
• The result: GhYP and GaYP promote epidermal cell expansion by upregulating brassinosteroid biosynthesis genes, increasing petal size, and rescuing small-petal phenotypes, advancing understanding of cotton petal development.