Isolation and Characterization of an APETALA1-Like Gene from Pear (Pyrus pyrifolia)

Abstract

To study the early steps of flower initiation and development in pear (Pyrus pyrifolia), a MADS-box gene, PpAP1, a putative APETALA1 (AP1) pear ortholog from Pyrus pyrifolia, was isolated. The deduced amino acid sequence of PpAP1 indicated high sequence identity with members of the MADS-box family of transcription factors, particularly the AP1/SQUA family of MADS-box proteins, which control floral-meristem and floral-organ identities. PpAP1 was expressed mainly in reproductive tissues such as inflorescence shoot apices and in flowers. Moreover, no transcription was detected in leaves, and only trace amounts were detected in vegetative shoot apices. In flowers, PpAP1 transcripts were restricted to the outer three whorls, mainly in sepals. mRNA expression patterns of PpAP1 suggest that it might play a role in both flowering and flower development. As low expression of PpAP1 was detected in stamens, this suggested that it was not an A-function gene. Overexpression of PpAP1 in Arabidopsis resulted in early-flowering phenotypes, thus indicating that PpAP1 played a similar role to that of its Arabidopsis homolog. Moreover, multiple floral organs were observed in transgenic lines, thus suggesting that PpAP1 has a broader role that than of classical A-function genes. These results indicated that PpAP1 plays important roles in regulating vegetative to reproductive development in plants, and is also involved in the development of floral organs.