MiABI5-like7- <i>MiFT3</i> regulatory module controls floral transition induced by mepiquat chloride in evergreen perennial mango ( <i>Mangifera indica</i> L.)

Abstract Regulating floral induction (FI) through the application of gibberellin (GA) biosynthesis inhibitors is a critical agricultural practice to prevent yield loss in fruit trees. We observed that mepiquat chloride (MC), a highly safe plant growth retardant, enhanced FI in mango. Nevertheless, the molecular mechanism by which MC facilitates FI remains elusive. Using two distinct treatments and varied stages during FI in mango (Mangifera indica L. ‘Tainong No.1’), 24 dynamic transcriptome profiles were constructed. Through pairwise comparisons and weighted gene co-expression network analysis (WGCNA), a regulatory network centered on the hub gene FLOWERING LOCUS T3 (MiFT3) was established. We further discovered MC-induced floral transition was associated with the decreases of GA20 and GA3 levels and the upregulation of MiGA2oxs (GA2 OXIDASES) expression, alongside the increase of abscisic acid (ABA) content and the upregulation of MiNCED1 (9-cis-epoxycarotenoid dioxygenase 1) and MiABI5-like7 (ABSCISIC ACID-INSENSITIVE 5-like7). Furthermore, biochemical assays and stable transgenic experiments were applied to confirmed that MiABI5-like7 activated the expression of MiFT3. Moreover, silencing MiABI5-like7 in mango buds delayed floral transition, while ectopic expression of MiABI5-like7 promoted early flowering. Additionally, exogenous ABA accelerated the floral transiton induced by MC, whereas an ABA inhibitor delayed floral transiton, which were associated with the expression levels of MiABI5-like7 and MiFT3. This study clarified the mechanism by which MC induced floral transition by inhibiting GA biosynthesis that activate MiABI5-like7-mediated signaling pathway, which provides novel insights into the regulatory network of FI in plants and offers a solution for solving the issue of insufficient flowering in warm winter climates.