Gibberellin-3 induced dormancy and suppression of flower bud formation in pitaya (Hylocereus polyrhizus)

Background: Flowering is a complex, finely regulated process involving multiple phytohormones and transcription factors. However, flowering regulation in pitaya (Hylocereus polyrhizus) remains largely unexamined. This study addresses this gap by investigating gibberellin-3 (GA3) effects on flower bud (FB) development in pitaya. Our findings reveal that GA3 application induces significant bud dormancy and suppresses FB formation, highlighting GA3's role in modulating flowering in this species.

Results: GA3 application during peak flowering period significantly altered hormone levels, reducing auxin (AUX), cytokinin (CTK) active forms dihydrozeatin riboside (dhZR), zeatin riboside (ZR), N6-isopentenyladenosine (iPA), and brassinosteroid (BR), while increasing jasmonic acid (JA), GA3, and gibberellin-4 (GA4) levels, with abscisic acid (ABA) levels remaining unchanged compared to control. Conversely, FB formation was associated with increased levels of AUX, dhZR, ZR, iPA, ABA, and JA, and decreased GA3 and GA4 levels. Transcriptomic analysis revealed batches of differentially expressed genes (DEGs) associated with phytohormone signal transduction, aligning with observed hormone changes. Notably, except four CONSTANS-like (CO) (HU06G02633, HU10G00019, HU04G00234, and HU02G01458), all other CO genes were preferentially active in GA3-treated buds. GA3 treatment inhibited genes linked to the ABC model (AP1, AP2, MADS-box, AGL, SPL) and floral identity genes (LFY, FT), favoring dormancy and clean sweep of FB formation.

Conclusion: These findings underscore the potential of GA3 as a powerful modulator of flowering and bud dormancy in pitaya. By elucidating the hormonal and genetic responses to GA3 treatment, this study contributes to our understanding of flowering regulation in pitaya and highlights the significant impact of GA3 on bud developmental pathways.