VcRR2 regulates chilling-mediated flowering through expression of hormone genes in a transgenic blueberry mutant

Abstract

The molecular mechanism underlying dormancy release and the induction of flowering remains poorly understood in woody plants. Mu-legacy is a valuable blueberry mutant, in which a transgene insertion caused increased expression of a RESPONSE REGULATOR 2-like gene (VcRR2). Mu-legacy plants, compared with nontransgenic ‘Legacy’ plants, show dwarfing, promotion of flower bud formation, and can flower under nonchilling conditions. We conducted transcriptomic comparisons in leaves, chilled and nonchilled flowering buds, and late-pink buds, and analyzed a total of 41 metabolites of six groups of hormones in leaf tissues of both Mu-legacy and ‘Legacy’ plants. These analyses uncovered that increased VcRR2 expression promotes the expression of a homolog of Arabidopsis thaliana ENT-COPALYL DIPHOSPHATE SYNTHETASE 1 (VcGA1), which induces new homeostasis of hormones, including increased gibberellin 4 (GA4) levels in Mu-legacy leaves. Consequently, increased expression of VcRR2 and VcGA1, which function in cytokinin responses and gibberellin synthesis, respectively, initiated the reduction in plant height and the enhancement of flower bud formation of the Mu-legacy plants through interactions of multiple approaches. In nonchilled flower buds, 29 differentially expressed transcripts of 17 genes of five groups of hormones were identified in transcriptome comparisons between Mu-legacy and ‘Legacy’ plants, of which 22 were chilling responsive. Thus, these analyses suggest that increased expression of VcRR2 was collectively responsible for promoting flower bud formation in highbush blueberry under nonchilling conditions. We report here for the first time the importance of VcRR2 to induce a suite of downstream hormones that promote flowering in woody plants.

Morphological, Physiological, and Molecular Responses of Sweetly Fragrant Luculia gratissima During the Floral Transition Stage Induced by Short-Day Photoperiod

“…Many studies have demonstrated that various phytohormones participate in the regulation of floral transition ( Shu et al, 2018 ; Lin et al, 2019 ; Zhang et al, 2019 ; Bao et al, 2020 ). A total of 20 (13.70%) DEGs associated with phytohormone metabolism were identified, and these involved 16 phytohormone metabolism homologous genes and were related to nine phytohormone metabolism pathways.…”

“…Phytohormones play important regulatory roles in plant development and the mechanisms of their participation in floral transition in many plants are extensively studied ( Shu et al, 2018 ; Lin et al, 2019 ; Zhang et al, 2019 ; Bao et al, 2020 ). However, the complex hormone regulatory network of floral transition in perennial woody plants remains unclear.…”

Morphological, Physiological, and Molecular Responses of Sweetly Fragrant Luculia Gratissima During the Floral Transition Stage Induced by Short-day Photoperiod

“…Many studies have demonstrated that various phytohormones participate in the regulation of oral transition [7,[14][15][16]. A total of 20 (13.70%) DEGs associated with phytohormone metabolism were identi ed, and these involved 16 phytohormone metabolism homologous genes and were related to nine phytohormone metabolism pathways.…”

“…Phytohormones play important regulatory roles in plant development and the mechanisms of their participation in oral transition in many plants are extensively studied [7,[14][15][16]. However, the complex hormone regulatory network of oral transition in perennial woody plants remains unclear.…”

Auxin-induced AUXIN RESPONSE FACTOR4 activates APETALA1 and FRUITFULL to promote flowering in woodland strawberry

“…Flowering marks a transition from vegetative to reproductive growth in plants and involves numerous physiological processes, metabolic pathways, and gene regulatory mechanisms 1 , 2 . These mechanisms involve intracellular and intercellular signal transduction cascades and the specific spatiotemporal expression of flowering genes 3 – 5 .…”