TrMADS3 , a new MADS-box gene, from a perennial species Taihangia rupestris (Rosaceae) is upregulated by cold and experiences seasonal fluctuation in expression level

In many temperate perennial plants, floral transition is initiated in the first growth season but the development of flower is arrested during the winter to ensure production of mature flowers in the next spring. The molecular mechanisms of the process remain poorly understood with few well-characterized regulatory genes. Here, a MADS-box gene, named as TrMADS3 , was isolated from the overwintering inflorescences of Taihangia rupestris , a temperate perennial in the rose family. Phylogenetic analysis reveals that TrMADS3 is more closely related to the homologs of the FLOWERING LOCUS C lineage than to any of the other MIKC-type MADS-box lineages known from Arabidopsis . The TrMADS3 transcripts are extensively distributed in inflorescences, roots, and leaves during the winter. In controlled conditions, the TrMADS3 expression level is upregulated by a chilling exposure for 1 to 2 weeks and remains high for a longer period of time in warm conditions after cold treatment. In situ hybridization reveals that TrMADS3 is predominately expressed in the vegetative and reproductive meristems. Ectopic expression of TrMADS3 in Arabidopsis promotes seed germination on the media containing relatively high NaCl or mannitol concentrations. These data indicate that TrMADS3 in a perennial species might have its role in both vegetative and reproductive meristems in response to cold.