A common role of GIGANTEA (GI)–CONSTANS (CO)–FLOWERING LOCUS T (FT) in Arabidopsis and rice has been demonstrated ( Izawa et al., 2002 Ryosuke et al., 2003). The inverse responses to daylength observed between Arabidopsis (LD plant) and rice (SD plant) are partly explained by the difference between the function of CO in Arabidopsis and the rice homolog HEADING DATE 1 ( Hd1) ( Izawa et al., 2002 Ryosuke et al., 2003). The DN plants flower interdependently of the photoperiodic conditions. In contrast, rice is considered a SD plant that flowers faster in SDs than in LDs. Arabidopsis is one of the well-known LD plants and flowers much earlier under LD than SD conditions. Based on their daylength requirements, plants are classified as long day (LD), short day (SD), or day-neutral (DN) ( Jeong and Clark, 2005 Srikanth and Schmid, 2011). The photoperiod pathway refers to the regulation of flowering in response to daylength. All these pathways finally converge on the common downstream flowering integrators FT ( FLOWERING LOCUS T) and SOC1 ( SUPPRESSOR OF OVEREXPRESSION OF CO1), whose expression leads to the induction of floral identity genes such as LFY ( LEAFY) and AP1 ( APETALA1), followed by flower bud formation and burst ( Fornara et al., 2010 Srikanth and Schmid, 2011). So far, six genetic pathways have been identified to control plant flowering, namely photoperiod, vernalization, ambient temperature, gibberellin, age, and autonomous pathways. The timely transition from vegetative to floral meristems in higher plants is programmed by external environmental cues and endogenous signals ( Langridge, 1957).
This finding established the molecular foundation of CF in roses and further shed light on the underlying mechanisms of DN responses.įlowering is a biological process indicating the shift from vegetative growth to reproductive development as such, its accurate timing is key to reproduction and survival. Taken together, the complementary expression of RcCO in LDs and of RcCOL4 in SDs guaranteed flowering under favorable growth conditions regardless of the photoperiod. Further analyses revealed that physical interaction between RcCOL4 and RcCO facilitated binding of RcCO to the CORE motif in the promoter of RcFT and induction of RcFT. Interestingly, in contrast to RcCO-silenced plants, the flowering time of RcCOL4-silenced plants was more delayed under SD than under LD conditions, indicating perturbed plant responses to day neutrality. Diminishing the expression of RcCO or/and RcCOL4 by virus-induced gene silencing (VIGS) delayed flowering time under both SDs and LDs. Here, RcCO and RcCOL4 were identified as floral activators up-regulated under LD and SD conditions, respectively, in the CF cultivar Rosa chinensis ‘Old-Blush’. Modern roses are economically important ornamental plants with continuous flowering (CF) features, and are generally regarded as DN plants. The inverse responses to daylength of LD and SD plants have been partly characterized in Arabidopsis and rice however, the molecular mechanism underlying the DN response is largely unknown. Our results not only revealed another layer of PIF functioning in the flowering of woody perennial plants, but also established a mechanism of light response in DN plants.Photoperiodic flowering responses are classified into three major types: long day (LD), short day (SD), and day neutral (DN). Furthermore, this inhibition was enhanced when RcPIFs were stabilized by LL, leading to delayed flowering under LL compared with HL. The RcPIFs interacted with the transcription factor CONSTANS (RcCO) to form a RcPIFs–RcCO complex, which interfered with the binding of RcCO to the promoter of FLOWERING LOCUS T ( RcFT), thereby inhibiting its expression. chinensis accelerated flowering under both LL and HL, with a more robust effect in LL, establishing RcPIFs as flowering suppressors in response to light intensity. Simultaneous silencing of three RcPIFs in R. The heterologous expression of RcPIF1, RcPIF3, or RcPIF4 in the Arabidopsis ( Arabidopsis thaliana) pifq quadruple mutant partially rescued the mutant’s shorter hypocotyl length. The time until flowering positively corresponded with the mRNA and protein levels of phytochrome-interacting factors (PIFs RcPIFs). Flowering was significantly delayed in the LL condition compared with the HL, but was not affected by EOD-FR treatment. s −1), and either with or without an end-of-day far-red (EOD-FR) treatment.Chinese rose ( Rosa chinensis) plants were grown under two light intensities (low light, 92 μmol As day-neutral (DN) woody perennial plants, the flowering time of roses ( Rosa spp.) is assumed to be independent of the photoperiodic conditions however, light responses of rose plants are not well understood.
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