Genome-wide identification, evolution, and expression analysis of the NPR1-like gene family in pears

The NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1) plays a master regulatory role in the salicylic acid (SA) signal transduction pathway and plant systemic acquired resistance (SAR). Members of the NPR1 -like gene family have been reported to the associated with biotic/abiotic stress in many plants, however the genome-wide characterization of NPR1 -like genes has not been carried out in Chinese pear ( Pyrus bretschneideri Reld). In this study, a systematic analysis was conducted on the characteristics of the NPR1 -like genes in P. bretschneideri Reld at the whole-genome level. A total nine NPR1- like genes were detected which eight genes were located on six chromosomes and one gene was mapped to scaffold. Based on the phylogenetic analysis, the nine PbrNPR1 - like proteins were divided into three clades (Clades I–III) had similar gene structure, domain and conserved motifs. We sorted the cis -acting elements into three clades, including plant growth and development, stress responses, and hormone responses in the promoter regions of PbrNPR1- like genes. The result of qPCR analysis showed that expression diversity of PbrNPR1- like genes in various tissues. All the genes were up-regulated after SA treatment in leaves except for Pbrgene8896 . PbrNPR1- like genes showed circadian rhythm and significantly different expression levels after inoculation with Alternaria alternata . These findings provide a solid insight for understanding the functions and evolution of PbrNPR1- like genes in Chinese pear.