Abstract
Rosa chinensis is one of the most popular flower plants worldwide. The recurrent flowering trait greatly enhances the ornamental value of roses, and is the result of the constant formation of new flower buds. Flower bud differentiation has always been a major topic of interest among researchers. The APETALA1 (AP1) MADS-box (Mcm1, Agamous, Deficiens and SRF) transcription factor-encoding gene is important for the formation of the floral meristem and floral organs. However, research on the rose AP1 gene has been limited. Thus, we isolated AP1 from Rosa chinensis ‘Old Blush’. An expression analysis revealed that RcAP1 was not expressed before the floral primordia formation stage in flower buds. The overexpression of RcAP1 in Arabidopsis thaliana resulted in an early-flowering phenotype. Additionally, the virus-induced down-regulation of RcAP1 expression delayed flowering in ‘Old Blush’. Moreover, RcAP1 was specifically expressed in the sepals of floral organs, while its expression was down-regulated in abnormal sepals and leaf-like organs. These observations suggest that RcAP1 may contribute to rose bud differentiation as well as floral organ morphogenesis, especially the sepals. These results may help for further characterization of the regulatory mechanisms of the recurrent flowering trait in rose.
Highlights
Roses, which are among the most popular flowers worldwide, have been cultivated in China since 3000 B.C
In the ABCDE model, APETALA1(AP1) and APETALA2(AP2) belong to A-functional genes and these genes are responsible for the formation of sepals in the first whorl [8,9]
Studies in Arabidopsis thaliana, Petunia hybrida, and Antirrhinum majus have revealed that MADS-box transcription factors regulate floral organ formation [11,12]
Summary
Roses, which are among the most popular flowers worldwide, have been cultivated in China since 3000 B.C. MADS-box proteins are important transcription factors in plants that play important roles in flower development and control the generation of flower organ, as is described in the ABCDE model [5,6,7]. Theissen et al (2001) put forward the tetrameric model of floral development in the MADS-box gene. Studies in Arabidopsis thaliana, Petunia hybrida, and Antirrhinum majus have revealed that MADS-box transcription factors regulate floral organ formation [11,12]. MADS-box orthologs involved in floral organ formation have been cloned and partially functionally verified, such as RhAP3, RhPI, and RhAG [13,14]. AP1 is a subfamily of the MADS-box gene that has been identified as a floral meristem gene, which induces floral development in many species [15,16]. The data presented may enrich our understanding of the flower formation mechanism in rose
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