Molecular cloning of two novel NPR1 homologue genes in coconut palm and analysis of their expression in response to the plant defense hormone salicylic acid

Nonexpressor of pathogenesis-related gene 1 (NPR1) codes for a transcription cofactor involved in the activation of systemic acquired resistance, a salicylic acid (SA)-dependent defense response. This work reports the cloning and characterization of two new genes, CnNPR1 and CnNPR3 from coconut, homologous to AtNPR1 of Arabidopsis thaliana. The cDNA deduced amino acid sequence contains the protein-protein interaction domains the BTB/POZ and ANKYRIN repeat domains, and a nuclear localization site (NLS). Phylogenetic analysis grouped CnNPR1 in a clade with AtNPR1 and CnNPR3 in a clade with AtNPR3, both reported genes of A. thaliana. Exogenous application of SA to coconut plantlets induced changes in the expression of CnNPR1 and CnNPR3 in leaf, stem and root tissues, providing evidence of their possible role in the signaling cascade leading to SAR in coconut palm. This is the first report on the cloning of putative key genes in the SAR-type defense mechanism in coconut palm.