Type-B response regulators MaRR_B9 and MaRR_B12 coordinate cytokinin-mediated negative regulation of anthocyanin biosynthesis in banana fruits

Abstract

O_LIAnthocyanins are pigments responsible for vibrant plant colors and play vital roles in plant physiology. Comparing two banana varieties, grand naine (GN) and red banana (RB), which display significant contrast in anthocyanin pigmentation. C_LIO_LITranscriptomic analysis of GN and RB peel and pulp tissue highlighted cytokinin-specific response regulators, MaRR_B9 and MaRR_B12, as regulators of anthocyanin biosynthesis. C_LIO_LIThrough a combination of physiological, molecular, and biochemical analyses, we demonstrate that MaRR_B9 and MaRR_B12 exert direct regulatory control over key structural genes of anthocyanin biosynthesis, dihydroflavanol reductase (MaDFR) and anthocyanidin synthase (MaANS). MaRR_B9 and MaRRB_12 interact with the promoters of MaDFR and MaANS, repressing the concerned genes in vivo. Overexpression of MaRR_B9 and MaRR_B12 in banana fruits leads to a reduction in anthocyanin content, particularly that of the cyanidin derivative, along with altered expression patterns of MaDFR and MaANS. C_LIO_LIThus, the present study identifies novel regulators of anthocyanin biosynthesis in banana and provides further evidence that the cytokinin regulatory network modifies anthocyanin accumulation in plants. In conclusion, our findings reveal new molecular targets, in the form of MaRRs for the genetic manipulation of anthocyanin content and thereby for the development of stress-resilient and nutritionally enriched crop plants. C_LI