Ectopic expression of a SOC1 homolog from Phyllostachys violascens alters flowering time and identity of floral organs in Arabidopsis thaliana

Abstract

PvMADS56 may regulate the flowering time, the identity of floral organs, and the development of leaves. As a floral activator, SUPPRESSOR OF OVEREXPRESSION OF CO1/AGAMOUS-LIKE 20 (SOC1/AGL20) 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 was 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 soc1 Arabidopsis. Meanwhile the transgenic plants displayed abnormal floral organs and leaves, low fertility and dwarfism. Overexpression of PvMADS56 in the wild-type Arabidopsis not only caused early flowering by upregulating Flowering Locus T and downregulating Flowering Locus C expression, but also led to abnormal floral organs by downregulating APETALA1, APETALA3, PISTILLATA, and AGAMOUS. Furthermore, PvMADS56 might be a nuclear protein, and interacted with PvAP1 and PvSEP3 from P. violascens in 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 but also involves in the identity of floral organs in response to ABA and MeJA.