Dataset Information

Wheat flowering repressor VRN2 and promoter CO2 compete for interactions with NUCLEAR FACTOR-Y complexes.

ABSTRACT: The transition from vegetative to reproductive development in the temperate cereals is mainly regulated by seasonal cues including vernalization (determined mainly by VRN1 and VRN2 genes) and photoperiod (determined mainly by PPD1 and CO2 genes). The wheat VRN3 gene, which is similar to Arabidopsis FT, plays a central role in the integration of the competing signals from these two pathways. Under long days, VRN3 transcription is down-regulated by VRN2, a unique flowering repressor in cereals, and up-regulated by CO2. Overexpression of VRN3 overcomes VRN2 repression and promotes VRN1 transcription and flowering initiation. Using yeast two- and three-hybrid assays we show here that the CCT domains present in VRN2 and CO2 proteins interact with the same subset of eight NF-Y proteins, and that these CCT proteins compete with NF-YA for interactions with NF-YB proteins. We have confirmed all these interactions in vitro, and the interactions between VRN2 and two of the three NF-YB proteins were further confirmed in planta. In addition, we show that mutations in the CCT domain of VRN2 that eliminate the vernalization requirement in winter wheat also reduce the strength of the interactions between VRN2 and NF-Y proteins, and the ability of VRN2 to compete with CO2. Taken together, our results suggest that the interactions between CCT and NF-Y proteins play an important role in the integration of the vernalization and photoperiod seasonal signals, and provide a flexible combinatorial system to integrate multiple developmental and environmental signals in the regulation of flowering initiation in the temperate cereals.

SUBMITTER: Li C

PROVIDER: S-EPMC4765905 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Wheat flowering repressor VRN2 and promoter CO2 compete for interactions with NUCLEAR FACTOR-Y complexes.

Li Chengxia C Distelfeld Assaf A Comis Alfio A Dubcovsky Jorge J

The Plant journal : for cell and molecular biology 20110621 5

The transition from vegetative to reproductive development in the temperate cereals is mainly regulated by seasonal cues including vernalization (determined mainly by VRN1 and VRN2 genes) and photoperiod (determined mainly by PPD1 and CO2 genes). The wheat VRN3 gene, which is similar to Arabidopsis FT, plays a central role in the integration of the competing signals from these two pathways. Under long days, VRN3 transcription is down-regulated by VRN2, a unique flowering repressor in cereals, an ...[more]

PMID: 21554456

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Project description:Most of the natural variation in wheat vernalization response is determined by allelic differences in the MADS-box transcription factor VERNALIZATION1 (VRN1). Extended exposures to low temperatures during the winter (vernalization) induce VRN1 expression and promote the transition of the apical meristem to the reproductive phase. In contrast to its Arabidopsis homolog (APETALA1), which is mainly expressed in the apical meristem, VRN1 is also expressed at high levels in the leaves, but its function in this tissue is not well understood. Using tetraploid wheat lines with truncation mutations in the two homoeologous copies of VRN1 (henceforth vrn1-null mutants), we demonstrate that a central role of VRN1 in the leaves is to maintain low transcript levels of the VRN2 flowering repressor after vernalization. Transcript levels of VRN2 were gradually down-regulated during vernalization in both mutant and wild-type genotypes, but were up-regulated after vernalization only in the vrn1-null mutants. The up-regulation of VRN2 delayed flowering by repressing the transcription of FT, a flowering-integrator gene that encodes a mobile protein that is transported from the leaves to the apical meristem to induce flowering. The role of VRN2 in the delayed flowering of the vrn1-null mutant was confirmed using double vrn1-vrn2-null mutants, which flowered two months earlier than the vrn1-null mutants. Both mutants produced normal flowers and seeds demonstrating that VRN1 is not essential for wheat flowering, which contradicts current flowering models. This result does not diminish the importance of VRN1 in the seasonal regulation of wheat flowering. The up-regulation of VRN1 during winter is required to maintain low transcript levels of VRN2, accelerate the induction of FT in the leaves, and regulate a timely flowering in the spring. Our results also demonstrate the existence of redundant wheat flowering genes that may provide new targets for engineering wheat varieties better adapted to changing environments.

Project description:BACKGROUND: As both abiotic stress response and development are under redox control, it was hypothesised that the pharmacological modification of the redox environment would affect the initial development of flower primordia and freezing tolerance in wheat (Triticum aestivum L.). RESULTS: Pharmacologically induced redox changes were monitored in winter (T. ae. ssp. aestivum cv. Cheyenne, Ch) and spring (T. ae. ssp. spelta; Tsp) wheat genotypes grown after germination at 20/17°C for 9 d (chemical treatment: last 3 d), then at 5°C for 21 d (chemical treatment: first 4 d) and subsequently at 20/17°C for 21 d (recovery period). Thiols and their disulphide forms were measured and based on these data reduction potentials were calculated. In the freezing-tolerant Ch the chemical treatments generally increased both the amount of thiol disulphides and the reduction potential after 3 days at 20/17°C. In the freezing-sensitive Tsp a similar effect of the chemicals on these parameters was only observed after the continuation of the treatments for 4 days at 5°C. The applied chemicals slightly decreased root fresh weight and increased freezing tolerance in Ch, whereas they increased shoot fresh weight in Tsp after 4 days at 5°C. As shown after the 3-week recovery at 20/17°C, the initial development of flower primordia was accelerated in Tsp, whereas it was not affected by the treatments in Ch. The chemicals differently affected the expression of ZCCT2 and that of several other genes related to freezing tolerance and initial development of flower primordia in Ch and Tsp after 4 d at 5°C. CONCLUSIONS: Various redox-altering compounds and osmotica had differential effects on glutathione disulphide content and reduction potential, and consequently on the expression of the flowering repressor ZCCT2 in the winter wheat Ch and the spring wheat Tsp. We propose that the higher expression of ZCCT2 in Ch may be associated with activation of genes of cold acclimation and its lower expression in Tsp with the induction of genes accelerating initial development of flower primordia. In addition, ZCCT2 may be involved in the coordinated control of the two processes.

Dataset Information

Wheat flowering repressor VRN2 and promoter CO2 compete for interactions with NUCLEAR FACTOR-Y complexes.

Publications

Wheat flowering repressor VRN2 and promoter CO2 compete for interactions with NUCLEAR FACTOR-Y complexes.

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