Hormone Signals Steer Flower Bud Formation in Lemon, Transcriptome Study Finds

Lemon trees decide when to flower through a hormonal balancing act, and a new transcriptome-based study has traced part of that circuitry in developing buds. Researchers examining lemon (Citrus limon (L.) Burm.) report that gibberellin acts as the major inhibitor of flower formation in this fruit tree, a role that differs significantly from the hormone’s behavior in model plants. Suppressing endogenous gibberellin formation, the study shows, is the key mechanism through which paclobutrazol (PBZ) promotes bud differentiation.

The team applied two contrasting treatments to lemon buds: gibberellic acid, which raises endogenous gibberellin content, and paclobutrazol, which blocks gibberellin biosynthesis. The outcomes ran in opposite directions. Paclobutrazol treatment markedly enhanced the number of flowering shoots, and this effect was associated with an elevated ratio of abscisic acid to zeatin riboside (ABA/ZR). Gibberellic acid did the reverse: application significantly elevated the endogenous gibberellic acid content and demonstrated inhibitory effects on bud differentiation.

To understand how these hormonal shifts propagate through gene networks, the researchers integrated metabolomic and transcriptomic analyses. Exogenous application of gibberellic acid led to differential gene expression and a significant increase in gibberellin content. Notably, genes associated with flowering within the circadian rhythm pathway exhibited reduced expression levels following gibberellic acid treatment, connecting the hormone’s anti-flowering effect to the plant’s internal clock.

The metabolite shifts were equally telling. Genes responding to gibberellic acid treatment were associated with a reduction in the levels of gibberellin A4, gibberellin A7, and isopentenyl adenosine, while gibberellin A3 and trans-zeatin riboside also featured among the altered metabolites. Together, these changes describe a coordinated reallocation of hormone pools as buds move between growth and flowering programs.

The findings, published as an open-access article in BMC Plant Biology, provide molecular insights into how gibberellic acid and paclobutrazol modulate lemon bud differentiation through hormone signal transduction and circadian rhythm pathways. The authors frame the work as offering a regulatory framework for flowering control in lemon, with the hormone signal transduction and circadian rhythm routes and the associated metabolite shifts now identified as the molecular features that accompany the switch between vegetative and reproductive bud development.

Subject of Research: Transcriptome-based analysis of the role of endogenous hormones in regulating flower development in lemon (Citrus limon (L.) Burm.)

Article Title: Transcriptome-based analysis of the role of endogenous hormones in regulating flower development in lemon (Citrus limon (L.) Burm.)

Article References: Dong, J., Li, J., Lai, X., Yang, D., Fu, X., Liu, H., Yang, H., Zhou, X., Zhang, J., Du, Y., & Li, J. (2026). Transcriptome-based analysis of the role of endogenous hormones in regulating flower development in lemon (Citrus limon (L.) Burm.). BMC Plant Biology. https://doi.org/10.1186/s12870-026-10209-1

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10209-1

Keywords: Transcriptome-based, analysis, role, endogenous, hormones, regulating, flower, development, lemon, Citrus, limon, Burm