Identification and Characterization of NPR1 and PR1 Homologs in orchids in Response to Multiple Hormones, Salinity and Viral Stresses.

The plant () and () genes play fundamental roles in plant immunity response, as well as abiotic-stress tolerance. Nevertheless, comprehensive identification and characterization of and homologs has not been conducted to date in orchids, a valuable industrial crop cultivated as ornamental and medicinal plants worldwide. Herein, three -like (referred to as , , and ) and two ( and ) genes were genome-widely identified from orchids. Sequence and phylogenetic analysis revealed that and were grouped closest to homologs in (sharing 81.98% identity) and (64.14%), while was classified into a distinct group with (57.72%). CsPR1-1 and CsPR1-2 were both grouped closest to PR1 and other monocot plants. Expression profiling showed that and were highly expressed in stem/pseudobulb and/or flower. Salicylic acid (SA) and hydrogen peroxide (HO) significantly up-regulated expressions , and while , and were significantly up-regulated by abscisic acid (ABA) or salinity (NaCl) stress. transcripts of entire mosaic virus (CymMV) genomic RNA were successfully transfected into protoplasts, and the CymMV infection up-regulated the expression of , and Additionally, these genes were transiently expressed in protoplasts for subcellular localization analysis, and the presence of SA led to the nuclear translocation of the CsNPR1-2 protein, and the transient expression of greatly enhanced the expression of . Collectively, the -mediated signaling pathway is SA-dependent, and confers to the defense against CymMV infection in orchids.