Gibberellin delays floral transition in cultivated strawberry via the coordinated modulation of photoperiod signaling and nitrogen metabolism

Abstract Gibberellins (GAs) play a critical role in regulating the balance between vegetative and reproductive growth in strawberries; however, the underlying molecular mechanisms remain largely unclear. In this study, a weekly foliar application of GA 3 was performed to plugs of the short-day strawberry cultivar ‘Ninglu’ ( Fragaria × ananassa ). During the vegetative growth stage, GA 3 treatment increased plant height by 57.7% and mean petiole length by 69.4%, in addition to enhancing the expansion of the leaf lamina and vascular tissues. Developmental analysis of the shoot apical meristem (SAM) revealed that GA 3 delayed floral transition: while all control plants initiated flower buds within 40 days, only 77% of GA 3 -treated plants did so. Transcriptional analysis showed that GA 3 significantly upregulated the expression of photoperiod-related genes in leaves, including GIGANTEA ( GI ), CONSTANS ( CO ), and FLOWERING LOCUS T 1 ( FT1 ), which activated floral integrators such as SUPPRESSOR OF OVEREXPRESSION OF CO 1 ( SOC1 ) and TERMINAL FLOWER 1 ( TFL1 ). These changes subsequently suppressed key floral activators ( APETALA1 , AP1 ; FRUITFULL , FUL ; and LEAFY , LFY ) in the SAM. Additionally, GA 3 influenced nitrogen partitioning in leaves by modulating the expression of genes associated with nitrogen metabolism ( NITRATE REDUCTASE , NR ; NITRITE REDUCTASE , NIR ; GLUTAMINE SYNTHETASE , GS ; and FD-GOGAT , GOGAT ), transport ( NITRATE TRANSPORTER 1.2/1.7 , NRT1.2/NRT1.7 ; and AMMONIUM TRANSPORTER 1.1 , AMT1.1 ), and flowering time control ( FERREDOXIN-NADP ( +) OXIDOREDUCTASE 1 , FNR1 ; and CRYPTOCHROME 1 , CRY1 ). These results suggest that GA 3 may delay floral transition in strawberries through the coordinated modulation of vegetative growth, photoperiod signaling, and nitrogen metabolism, providing mechanistic insights into GA-mediated flowering control and offering potential implications for cultivation management.