Abstract
Flowering time is known to be regulated by numerous pathways, such as the autonomous, gibberellin, aging, photoperiod-mediated, and vernalization pathways. These regulatory mechanisms involve both environmental triggers and endogenous hormonal cues. Additional flowering control mechanisms mediated by other phytohormones, such as auxin, are less well understood. We found that in cultivated strawberry (Fragaria × ananassa), the expression of auxin response factor4 (FaARF4) was higher in the flowering stage than in the vegetative stage. Overexpression of FaARF4 in Arabidopsis thaliana and woodland strawberry (Fragaria vesca) resulted in transgenic plants flowering earlier than control plants. In addition, FveARF4-silenced strawberry plants showed delayed flowering compared to control plants, indicating that FaARF4 and FveARF4 function similarly in regulating flowering. Further studies showed that ARF4 can bind to the promoters of the floral meristem identity genes APETALA1 (AP1) and FRUITFULL (FUL), inducing their expression and, consequently, flowering in woodland strawberry. Our studies reveal an auxin-mediated flowering pathway in strawberry involving the induction of ARF4 expression.
Highlights
Flowering marks a transition from vegetative to reproductive growth in plants and involves numerous physiological processes, metabolic pathways, and gene regulatory mechanisms[1,2]
Since miR390 negatively regulates the expression of ARF3/4, we speculated that ARF3/4 may be related to flowering in cultivated strawberry
ARF4 is involved in the IAA-mediated flowering pathway in strawberry
Summary
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[3,4,5]. To elucidate the molecular underpinnings of flowering, many studies have been performed on the model species Arabidopsis thaliana, resulting in the identification of genes involved in flowering regulation, as well as multiple signaling pathways: photoperiodic, vernalization, ambient temperature, autonomous, aging, and gibberellin (GA)[6,7,8]. In A. thaliana, ARF functions have been well studied, and it is known that AtARF1, AtARF2, AtARF6, and AtARF8 are involved in floral organ development[14], while AtARF7, AtARF16, and AtARF19 are associated with root development[13,15], AtARF12-15 regulates embryogenesis and seed development, and AtARF20-22 has similar functions to AtARF12-1513,16
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