# Transcriptomics and Plant Hormone Analysis Reveal the Mechanism of Exogenous GA3 Promoting Reflowering of Phalaenopsis ‘Hatuyuki’

## TL;DR

Exogenous GA3 application promotes reflowering in Phalaenopsis orchids by influencing growth and hormone signaling pathways.

## Contribution

This study identifies key genes and hormone pathways involved in GA3-induced reflowering in Phalaenopsis ‘Hatuyuki’.

## Key findings

- Exogenous GA3 promotes reflowering in Phalaenopsis ‘Hatuyuki’ by enhancing starch and sugar accumulation.
- Transcriptome analysis reveals 3891 differentially expressed genes, with key hormone signaling genes validated.
- Core DEGs and hormone pathways provide new insights into GA3-regulated reflowering mechanisms.

## Abstract

Phalaenopsis orchids are globally significant high-value ornamental flowers due to their strange flower shape, gorgeous color, and long flowering period. The successful implementation of reflowering technology is expected to double the economic value of the Phalaenopsis industry. This study selected the cultivated variety Phalaenopsis ‘Hatuyuki’ as the material to investigate the effects of exogenous gibberellin A3 (GA3) application (0, 50, 100, 150, and 200 mg/L) on its reflowering. Growth phenotype analysis indicates that exogenous GA3 significantly promotes the occurrence of reflowering in Phalaenopsis ‘Hatuyuki’ after the first flowering, specifically manifested in elongated leaves, flower bud differentiation, flower stalk growth, and an earlier onset of flowering. The application of exogenous GA3 significantly enhances the accumulation of starch, soluble sugars, and proteins in Phalaenopsis ‘Hatuyuki’, while inhibiting the synthesis of free fatty acids. Gibberellins (GA3, gibberellin A1 (GA1), and gibberellin A8 (GA8)), cytokinins (6-Benzyladenosine (BAPR) and Kinetin (K)), and indole-3-acetic acids (IAAs) (tryptamine (TRA), indole-3-acetic acid (IAA)) are the core endogenous hormones responding to exogenous GA3 spraying treatment. Transcriptome analysis identified a total of 3891 differentially expressed genes (DEGs). The KEGG enrichment analysis revealed that the most significantly enriched KEGG pathways included ‘Plant hormone signal transduction’. Key genes involved in the plant hormone signal transduction pathway (AUX, IAA, SAUR, DELLA, MYC2) were validated through qRT-PCR, suggesting that these genes may be crucial for the exogenous GA3 application that promotes the reflowering of Phalaenopsis ‘Hatuyuki’. Additionally, this study highlights 202 core DEGs responsive to exogenous GA3. Combined with the analysis of hormone signaling pathways, it provides a new perspective for uncovering the key molecular modules involved in GA3-regulated reflowering of Phalaenopsis ‘Hatuyuki’. Overall, the findings of this study indicate that exogenous GA3 application can promote the re-flowering of Phalaenopsis ‘Hatuyuki’.