Cloning And Expression Analysis Of Genes Correlated With Light Induced Coloration In Apple Fruit

Apple is one of the most important fresh fruits worldwide.Peel color is an important component for fruit quality.To get insight into the mechanism underlying apple fruit coloration,we cloned the full-length cDNAs of five coloration-related genes and the promoter regions of two contructive genes, and analyzed their expression level in the peel of bagging apple fruits exposed to natural light.The results are shown as follows.1.Full-length cDNAs of 5 important genes,i.e.MdMYB1,MdCRY1, MdCRY2,MdCOP1-1 and MdCOP1-2,associated with apple coloration,as well as the promoter regions of two contructive genes MdDFR and MdUFGT for anthocyanin biosynthesis,were isolated from apple.The full-length cDNA of MdCRY1 is 2310 bp in size.Its ORF encoded 680 amino acid residues.The protein is predicated to be 76.6 kD in molecular weight and 5.3 in pI,and contains a conserved FAD domain.Compared with other plant homologs in GenBank,MdCRY1 showed＞60%identity at amino acid level to its counterparts from other plant species,especially up to 83.5%to grapevine CRY1 protein.The full-length cDNA of MdCRY2 is 2102 bp in size and encodes 648 amino acid residues.The molecular weight and pI of the predicted protein are 73.5 kD and 5.7,respectively.The predicted protein contains a conserved FAD domain and a DNA photolyase domain.The full-length cDNA of MdCOP1-1 is 2087 bp in size.Its ORF encodes a protein containing 665 amino acid residues with molecular weight 74.7 kD and pI 6.4.The predicted protein contains a conserved WD-40 motif.The full-length cDNA of MdCOP1-2 is 2213 bp in size.Its ORF encodes 659 amino acid residues.The predicated MdCOP1-2 protein contains a conserved WD-40 motif.Its molecular weight and pI are 74.2 kD and 6.2, respectively.The full-length cDNA of MdMYB1 is 865 bp in size.Its ORF encodes 243 amino acid residues.The predicted MdMYB1 protein contains conserved R2R3 motifs.The promoters of MdDFR and MdUFGT are 1145 bp and 1674 bp in size,respectively.There exist conserved cis-acting elements,i.e.MRE, MBS and MBSI in two promoters,to which MYB transcription factors possibly bind.2.Light exposure induces the expression of MdMYBI,MdDFR and MdUFGT genes.Three genes show the similar expression pattern.3.Both MdCRY1 and MdCRY2 genes are expressed in a similar pattern in the peel of bagging apple fruits upon exposed to light treatment.4.Along with the triggering or regulation by light treatment,anthocyanin gradually accumulates in peel,and fruits turn red in color.