Abstract
The rotation of the earth results in periodic changes in environmental factors such as daylength and temperature; the circadian clock is the endogenous mechanism responsible for day-length measurement, and allows plants to anticipate these fluctuations and modulate their developmental programs to maximize adaptation to those environmental cues. Flowering represents the transition from a vegetative to reproductive phase and is controlled by complex and highly regulated genetic pathways. In many plants, the time of flowering is strongly influenced by photoperiod, which synchronizes the floral transition with the favourable season of the year. Over the last decade, genetic approaches have aided the discovery of many signalling components involved in the photoperiod pathway and here, we highlight the significant progress made in identifying the molecular mechanisms that measure daylength and control flowering initiation in Arabidopsis, a long day (LD) plant, and in rice, a short day (SD) plant. Some components of the Arabidopsis regulatory network are conserved in other species, but the difference in the function of particular genes may contribute to the opposite photoperiodic flowering response observed between LD and SD plants. The specific regulatory mechanisms involved in controlling CONSTANS (CO) expression and stability by the circadian clock and the different photoreceptors will be described. In addition, the role of FLOWERING LOCUS T (FT), as part of the florigen, and several other light signalling and circadian-dependent components in photoperiodic flowering will be also discussed.
Highlights
The rotation of the earth results in periodic changes in environmental factors such as daylength and temperature; the circadian clock is the endogenous mechanism responsible for day-length measurement, and allows plants to anticipate these fluctuations and modulate their developmental programs to maximize adaptation to those environmental cues
In long day (LD) plants flowering is promoted by daily periods of light longer than a critical daylength, whereas plants that accelerate flowering in response to daylength below a critical threshold are called short day (SD) plants
This florigen was defined as a graft-transmissible substance(s) that is generated in the leaves in response to photoperiodic inductive conditions and moves through the phloem to stimulate the initiation of flowering in the shoot apical meristem (SAM)
Summary
Daylength measurement depends on the ability of plants to detect light and the existence of a timekeeping mechanism referred to as the circadian clock. The plant circadian system consists of input pathways that provide temporal information to the clock, the central oscillator mechanism itself, responsible for driving rhythms with a period close to 24 h, and a number of output pathways that regulate metabolic and developmental processes using the temporal information provided by the clock; the participation of the circadian clock in the control of biological activities allows plant species to anticipate and adapt to periodic environmental changes, maximizing their opportunities to survive successfully (Mas, 2005; McClung, 2006; Hotta et al, 2007) (Fig. 1). The control of flowering by daylength is a key determinant of seasonal patterns of flowering, and is a process regulated by one or more of these output branches of the clock. To measure daylength and achieve this photoperiodic regulation, the core oscillator determines the daily rhythms in output genes, and these can set the light sensitive phase for triggering the floral transition when plants are exposed to appropriate photoperiodic conditions
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
