Cloning and expression analysis of an MYB gene associated with calyx persistence in Korla fragrant pear.

We isolated an MYB-like gene from Korla fragrant pear using differential display RT-PCR. Expression of this gene in flowers appears to be correlated with calyx persistence. Korla fragrant pear (Pyrus brestschneideri Rehd) is an economically important pear cultivar in China. A persistent calyx results in the deformation of the fruit. We used differential display RT-PCR to obtain 42 cDNA fragments from Korla fragrant pear flowers. Alignments of nucleotide and amino acid sequences suggested that two fragments (kfp1and kfp4) were related to calyx persistence. The fragments were 78% homologous with Malus × domestica SPL transcription factor (SPL3) and 83% homologous with Malus × domestica MYB transcription factor (MYB12). The complete cDNA sequence of kfpMYB was determined to clarify the role of MYB in calyx persistence. kfpMYB contained a 116 bp 5'-UTR, a 1122 bp open reading frame encoding 374 amino acids, and a 319 bp 3'-UTR. The nucleotide and amino acid sequences of the cDNA in Korla fragrant pear were highly homologous with those of MYB transcription factors in other plant species, suggesting that the sequence is a MYB transcription factor gene. The abundance of kfpMYB mRNA varied significantly between the second and fourth flowers on the branch. Furthermore, kfpMYB expression changed significantly during anthesis and was significantly higher in Jinfeng pear (persistent calyx) and Korla fragrant pear than in Yali pear (deciduous calyx). Expression of kfpMYB was significantly reduced by naphthalene (NAA), abscisic acid (ABA), PBO, and paclobutrazol (PP333). Uniconazole, ethylene (ETH), and gibberellic acid (GA3) had no signicant effect on kfpMYB expression. In conclusion, the expression of kfpMYB appears to be correlated with calyx persistence in Korla fragrant pear.