The Role of Theobroma cacao NPR1 and NPR3 Genes in the Positive and Negative Regulation of the Plant Immune System

The Arabidopsis NON-EXPRESSOR OF PR1 (NPR1) gene encodes a transcription coactivator that plays a central role in regulating the transcriptional response to plant pathogens through SA dependent and independent pathways. A related gene, NPR3, functions as a receptor of the plant hormone salicylic acid and negatively regulates NPR1 function through proteosomal degradation of NPR1. We have demonstrated that Arabidopsis NPR3 plays an important role as a regulator of defense responses during flower development [1].  We will present recent advances in the functional characterization of these two Arabidopsis genes, and their orthologs in Theobroma cacao.  Using a Translational Biology approach and taking advantage of the cacao genome sequence, we have isolated related genes from cacao and performed functional analysis using several approaches.  Our data indicate that the TcNPR1 [2] and TcNPR3 are functional orthologs (paralogs) of Arabidopsis NPR1 and NPR3, and are likely to play a major role in the regulation of defense response in cacao .  This fundamental knowledge can contribute to breeding of disease resistant cacao varieties through the application of molecular markers towards pyramiding of resistance genes.

1.         Shi Z, Maximova S, Liu Y, Verica J, Guiltinan MJ: The Salicylic Acid Receptor NPR3 Is a Negative Regulator of the Transcriptional Defense Response during Early Flower Development in Arabidopsis. Molecular Plant 2012, doi: 10.1093/mp/sss091.

2.         Shi Z, Maximova S, Lui Y, Verica J, Guiltinan M: Functional Analysis of the Theobroma cacao NPR1 Gene in Arabidopsis. BMC Plant Biology 2010, 10:248.