Abstract
Plants integrate widely fluctuating temperatures to monitor seasonal progression. Here, we investigate the temperature signals in field conditions that result in vernalisation, the mechanism by which flowering is aligned with spring. We find that multiple, distinct aspects of the temperature profile contribute to vernalisation. In autumn, transient cold temperatures promote transcriptional shutdown of Arabidopsis FLOWERING LOCUS C (FLC), independently of factors conferring epigenetic memory. As winter continues, expression of VERNALIZATION INSENSITIVE3 (VIN3), a factor needed for epigenetic silencing, is upregulated by at least two independent thermosensory processes. One integrates long-term cold temperatures, while the other requires the absence of daily temperatures above 15 °C. The lack of spikes of high temperature, not just prolonged cold, is thus the major driver for vernalisation. Monitoring of peak daily temperature is an effective mechanism to judge seasonal progression, but is likely to have deleterious consequences for vernalisation as the climate becomes more variable.
Highlights
Plants integrate widely fluctuating temperatures to monitor seasonal progression
In Arabidopsis, vernalisation involves the epigenetic silencing of FLOWERING LOCUS C (FLC) by the conserved Polycomb Repressive Complex 2 (PRC2) in combination with PHD proteins, including cold-induced VERNALIZATION INSENSITIVE3 (VIN3)[1,2,3,4,5]
We monitored the temperature and the expression of FLC and VIN3 to measure the progress of vernalisation in the standard vernalisation-requiring Arabidopsis thaliana genotype Col FRISF2 (Fig. 1b, c)
Summary
Plants integrate widely fluctuating temperatures to monitor seasonal progression. Here, we investigate the temperature signals in field conditions that result in vernalisation, the mechanism by which flowering is aligned with spring. Expression of VERNALIZATION INSENSITIVE3 (VIN3), a factor needed for epigenetic silencing, is upregulated by at least two independent thermosensory processes. Plants use prolonged cold exposure to align the transition to flowering with spring, a process called vernalisation. In Arabidopsis, vernalisation involves the epigenetic silencing of FLOWERING LOCUS C (FLC) by the conserved Polycomb Repressive Complex 2 (PRC2) in combination with PHD proteins, including cold-induced VERNALIZATION INSENSITIVE3 (VIN3)[1,2,3,4,5]. Vernalisation can occur at constant temperatures between 0 and 15 °C6–8, but plants in the field experience daily fluctuations of more than 10 °C, equivalent in some locations (e.g. Norwich, UK) to the difference in average temperature between autumn and winter. The absence of warmth is a key signal of winter for Arabidopsis
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