Isolation and Characterization of IbNPR1 Gene from Sweet Potato (Ipomoea batatas)

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.

摘 要在植物系统获得性抗性(SAR)中, NPR1蛋白是水杨酸(SA)介导的基因表达中关键调控因子。本研究以甘薯品种青农2号为试验材料, 利用同源序列法和RACE技术分离甘薯SAR途径的主要抗病信号元件NPR1 (none expresser of PR gene)的全长cDNA序列。序列分析表明, IbNPR1基因全长2 353 bp, 包含一个编码586个氨基酸残基的开放阅读框, 包含有类似拟南芥NPR1蛋白中的BTB/POZ和锚蛋白重复氨基酸序列结构域。聚类分析显示, IbNPR1与来源于番茄的NPR1蛋白关系最近。Southern杂交及半定量RT-PCR分析表明, 甘薯NPR1基因属于低拷贝基因家族, 表达模式为组成型表达, 并且SA能提高其表达水平。推测IbNPR1可能在甘薯抵御病原物的侵染中起重要的作用。