Identification and molecular characterisation of the necrosis and ethylene-inducing peptide 1-like proteins (NLPs) of Phytophthora cinnamomi

Abstract

This research began with identifying the total number of NLP-encoding genes from the P. cinnamomi transcriptome. Phylogenetic analysis was performed in conjunction with expression analysis from previously generated RNA-seq data of P. cinnamomi infection of two avocado rootstocks. Seven candidate genes were selected, based on the presence of the NLP motif, expression patterns of the genes and their phylogenetic similarities to known NLPs. The coding sequence for these candidates were confirmed with Sanger sequencing after cloning into E. coli. The resulting protein structures were visualised and analysed for similarity and an attempt was made to ascertain functionality, however, more research is needed to determine this. This study also investigated the genes responsible for ethylene production in plants to find a relationship between P. cinnamomi infection and ethylene induction. The same RNA-seq data was used to identify and assess the genes encoding the three enzymes for ethylene biosynthesis and their expression during infection. The findings from this study provide a solid framework for future research into the molecular mechanisms of action of the NLPs during infection. The individual functions of P. cinnamomi NLPs have yet to be discovered and the understanding of which NLPs act under which mechanisms is still a mystery.