Abstract
The MADS-box gene APETALA 1 (AP1) plays essential roles in floral initiation and floral organ development. Here, we cloned the coding sequence (CDS) and promoter of CmAP1, the homolog of AP1 from Chinese chestnut (Castanea mollissima), an economically and ecologically important woody nut crop. The CDS of CmAP1 is 741 bp and encodes a 346–amino acid protein. Subcellular analysis revealed that CmAP1 localized to the nucleus. GUSdriven by the CmAP1 promoter was expressed in seedlings and in leaf margins, petals, and carpels of transgenic Arabidopsis (Arabidopsis thaliana). RNA in situ hybridization indicated that CmAP1was expressed in the inflorescence meristem, floral meristem, sepal, petal, and stamen and carpel primordia during the early stage of flower development. In mature female flowers, CmAP1 was expressed only in sepals and petals. In mature male flowers, CmAP1 was also expressed in stamens. An auxin response element (TGA element), jasmonic acid response element (TGACG motif), and WRKY binding site (W-box element) were identified in the CmAP1 promoter. Furthermore, the heterologous expression of CmAP1 promoted flowering and rescued the petal defect of the Arabidopsis ap1-11 mutant. These findings suggest that CmAP1 influences flowering time and flower development by functioning as a class A gene in C. mollissima.