Isolation and characterization of IbNPR1 gene from sweet potato (Ipomoea batatas).

Abstract NPR1 (nonexpressor of pathogenesis-related genes 1) protein is a key regulator of salicylic acid (SA)-mediated gene expression in systemic acquired resistance (SAR). Using homologous cloning and rapid amplification of cDNA ends (RACE) techniques, a full-length cDNA of IbNPR1 ( Ipomoea batatas nonexpressor of pathogenesis-related genes 1) was isolated from sweet potato cultivar Qingnong 2. The full-length cDNA is 2353 bp in length, which includes an open reading frame putatively encoding a polypeptide of 586 amino acids residues with a predicted molecular mass of 64.851 kD. The deduced amino acid sequence shared structural features with known NPR1 (-like) proteins: ankyrin repeat and BTB/POZ. Furthermore, phylogenetic analysis showed that IbNPR1 had the closest association with LeNPR1 from Lycopersicon esculentum . Southern blotting analysis revealed that IbNPR1 belongs to low-copy gene family in sweet potato. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis indicated that IbNPR1 was constitutively expressed in roots, stems, and leaves. In addition, IbNPR1 could be induced by salicylic acid. These results suggest that IbNPR1 plays an important role in response to pathogen infections in sweet potato.