Molecular cloning of a putative gene encoding isopentenyltransferase from pingyitiancha (Malus hupehensis) and characterization of its response to nitrate
1. College of Horticulture Science and Engineering/State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai’an,
Shandong 271018, P.R. China / 2. Corresponding author () / Received October 10, 2007; accepted December 4, 2007; published online April 1, 2008
Summary
A putative isopentenyltransferase (IPT) encoding gene was identified from a pingyitiancha (Malus hupehensis Rehd.) expressed sequence tag database, and the full-length gene was cloned by RACE. Based on expression profile and sequence
alignment, the nucleotide sequence of the clone, named MhIPT3, was most similar to AtIPT3, an IPT gene in Arabidopsis. The full-length cDNA contained a 963-bp open reading frame encoding a protein of 321 amino acids with a molecular mass of
37.3 kDa. Sequence analysis of genomic DNA revealed the absence of introns in the frame. Quantitative real-time PCR analysis
demonstrated that the gene was expressed in roots, stems and leaves. Application of nitrate to roots of nitrogen-deprived
seedlings strongly induced expression of MhIPT3 and was accompanied by the accumulation of cytokinins, whereas MhIPT3 expression was little affected by ammonium application to roots of nitrogen-deprived seedlings. Application of nitrate to
leaves also up-regulated the expression of MhIPT3 and corresponded closely with the accumulation of isopentyladenine and isopentyladenosine in leaves.
