Cloning, expression, and characterization of phyA gene from Ipomoea batatas

Phytochrome A (phyA), as a photoreceptor, has a profound influence on plant growth and development and participates in many important physiological processes, such as seed germination, seeding deetiolation, and flowering. On the basis of transcriptome database of sweet potato (Ipomoea batatas (L.) Lam.), phyA gene was cloned and sequenced. The gene has an open reading frame (ORF) of 3384 bp, encodes a protein with 1127 amino acid residues and a mol wt of 125.03 kD. More interestingly, it was found that there were three highly homologous phyA cDNA isoforms in sweet potato. In addition, when the genomic sequence of phyA gene was obtained by PCR using sweet potato genomic DNA as a template, it contained 4 exons and 3 introns with a total size of 4957 bp. The cDNA of phyA gene was inserted into the vector pET-32a(+) and successfully expressed in Escherichia coli BL21(DE3). The results of quantitative real-time PCR indicated that the expression level of phyA gene was higher in stem, followed by leaf, and the lowest in tuberous root. Besides, the expression of phyA mRNA in the mature leaf showed an obvious circadian rhythm in a day: mRNA accumulation gradually increased in darkness and decreased in the daylight.