Abstract
The appropriate timing of flowering is crucial for plant reproductive success. Studies of the molecular mechanism of flower induction in the model plant Arabidopsis thaliana showed long days and vernalization as major environmental promotive factors. Noccaea caerulescens has an obligate vernalization requirement that has not been studied at the molecular genetics level. Here, we characterize the vernalization requirement and response of four geographically diverse biennial/perennial N. caerulescens accessions: Ganges (GA), Lellingen (LE), La Calamine (LC), and St. Felix de Pallières (SF). Differences in vernalization responsiveness among accessions suggest that natural variation for this trait exists within N. caerulescens. Mutants which fully abolish the vernalization requirement were identified and were shown to contain mutations in the FLOWERING LOCUS C (NcFLC) and SHORT VEGETATIVE PHASE (NcSVP) genes, two key floral repressors in this species. At high temperatures, the non-vernalization requiring flc-1 mutant reverts from flowering to vegetative growth, which is accompanied with a reduced expression of LFY and AP1. This suggested there is “crosstalk” between vernalization and ambient temperature, which might be a strategy to cope with fluctuations in temperature or adopt a more perennial flowering attitude and thus facilitate a flexible evolutionary response to the changing environment across the species range.
Highlights
The transition from vegetative to reproductive growth is an important event in the plant’s life cycle and is determined by an interaction between developmental programs and pathways that respond to environmental cues such as day length and temperature (Andrés and Coupland, 2012)
Eight weeks of vernalization shortened the days to bolting in all accessions and increased the inflorescence numbers compared with 6 weeks of vernalization (Figure 1C)
Our results provide evidence that vernalization requirement and response among accessions vary within this species (Figure 1)
Summary
The transition from vegetative to reproductive growth is an important event in the plant’s life cycle and is determined by an interaction between developmental programs and pathways that respond to environmental cues such as day length and temperature (Andrés and Coupland, 2012). In winter-annual A. thaliana accessions, the promotion of flowering by vernalization is controlled by the interaction of floral repressors such as FLOWERING LOCUS C (FLC), FRIGIDA (FRI), and Flowering Time Control in Noccaea caerulescens. Its expression can be activated by FRI, which acts as part of a transcription complex that binds to the FLC promoter (Choi et al, 2011). SHORT VEGETATIVE PHASE (SVP) is another negative regulator of the floral transition (Hartmann et al, 2000). It is a MADS box transcription factor, repressing flowering either in a transcriptional complex with FLC or independent from the latter (Mateos et al, 2015)
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