Cloning And Functional Analysis Of SVP-like And SOC1-like Genes From Phyllostachys Violascens

Flowering of bamboo differs from many other plants as it is hard to predict its flowering time. It may take up to 120 years to bloom but it could occur next month, moreover, bamboo dies after it flowers, which brings the difficult for disclosing the bamboo flowering. In addition, the death of bamboo forest cause a great economic loss. Thus, the molecular mechnism of bamboo flowering with important theoretical and economic values should to be studied. In Arabidopsis thaliana, SHORT VEGETATIVE PHASE (SVP) and SUPPRESSOR OF OVEREXPRESSION OF CO1 (SOC1) as the integrators play an important role in flowering. In this paper, the SVP-like and SOC1-like genes were cloned from Ph. violascens and their functions were also verified by further experiments. The main research results are as follows:1. Two SVP homologs and one SOC1 homologs were identified from Ph. violascens, and named them as PvSVPl, PvSVP2 and PvMADS56, respectively.2. Sequence comparison and phylogenetic analysis showed that PvSVP1 and PvSVP2 were grouped with the SVP-like protein from grass familiy. PvSVPl or PvSVP2 is closely related to OsMADS55 or OsMADS47, respectively. PvSVPl and PvSVP2 was widely expressed in all the tested tissues of flowering and non-flowering bamboo plants, and their function was investigated by ectopic expression in transgenic Arabidopsis plants. The results showed that the PvSVPl overexpression in wild-type Arabidopsis promoted flowering under long and short days. Meanwhile the 35S::PvSVP1 transgenic Arabidopsis plants displayed abnormal floral organs and dwarfism. Overexpression of PvSVP1 in the wild-type Arabidopsis caused not only early flowering by upregulating FT and downregulating FLC expression, but also abnormal floral organs by upregulating API, AP3, and PI.To further recapitulate the function of PvSVPl, PvSVP1 was tranformed into rice that is another member in the same grass family as bamboo. Under long days, overexpression of PvSVPl in wild-type rice caused the phenotype of delayed flowering by indirectly downregulating Hd3a, RFT1, OsMADS50 and upregulating Ghd7 expression. By contrast, under short days overexpression of PvSVPl in wild-type rice caused early flowering by indirectly downregulating Ghd7 and upregulating Hd3a, RFT1, OsMADS50 expression. Meanwhile,35S::PvSVPl transgenic rice plants showed short panice and dwarfism. Overexpression of PvSVP2 in wild-type Arabidopsis plants also caused early flowering and abnormal floral organs. In addition, PvSVP1 and PvSVP2 were nuclear proteins, and could interact with PvAP1、PvVRN1、PvMADS56 and PvSEP3 from Ph. violascens by the yeast two-hybrid and BIFC assay. PvSVP1 and PvSVP2 were soluble by prokaryotic expression analysis.Taken together, similar as other SVP-like genes, PvSVPl and PvSVP2 involve the development of floral organs, while the difference is the effect on regulating flowering time.3. As a floral activator, SOC1 gene plays a key role in the flowering pathway of Arabidopsis. Bamboo MADS box gene PvMADS56, a homolog of SOC1/AGL20, was cloned from Phyllostachys violascens. Sequence comparison and phylogenetic analysis showed that PvMADS56 is closely related to MADS56-like proteins, which are the members of SOC1-like family. PvMADS56 was widely expressed in all the tested tissues of flowering and non-flowering bamboo plants, and its function was investigated by ectopic expression in transgenic Arabidopsis plants. The results showed that the overexpression promoted flowering in wild-type Arabidopsis and complemented the delayed flowering phenotype of socl Arabidopsis. Meanwhile the transgenic plants displayed abnormal floral organs and leaves, low fertility and dwarfism. Overexpression of PvMADS56 in the wild-type Arabidopsis caused not only early flowering by upregulating FT and downregulating FLC expression, but also abnormal floral organs by downregulating API, AP3, PI, and AG. Further, PvMADS56 was a nuclear protein, and could interact with PvAP 1 and PvSEP3 from Ph. violascens by the yeast two-hybrid assay. In addition, the activity of PvMADS56 promoter was enhanced by exogenous abscisic acid (ABA) and methyl jasmonate (MeJA). Taken together, PvMADS56 may be a multifunctional gene that not only regulates the flowering time and but involves also the identity of floral organs in response to ABA and MeJA.This study will provide information to reveal the mechanism by which bamboo flowers.