Studying the Persea americana-Phytophthora cinnamomi Interaction using High-Throughput Sequencing and Expression Profiling of Defence-Related Genes

One of the most serious threats to the avocado industry is Phytophthora root rot caused by Phytophthora cinnamomi (Pc). Despite the economic importance of avocado (Persea americana) to countries such as the USA and South Africa, and the impact of Pc, there is a lack of knowledge on the molecular level for this host-pathogen interaction. The aims of this study were to gain insight into the molecular defence response of avocado to Pc and to identify genes related to tolerance against PRR. To achieve this EST data was generated from pre-infected and post-infected avocado feeder root cDNA libraries using a single lane on the GS-FLX platform and expression of several defence-related genes was then studied. The study produced 2.0 Mb of sequence data consisting of 10 000 reads. These reads were then assembled into contigs, resulting in 367 novel sequences for Persea americana. More than 20 putative defence-related genes were identified of which 10 were selected and quantified. Genes such as metallothionein, thaumatin and the pathogenesis related protein PsemI were found to be differentially regulated. The sequence data generated, along with additional data, will contribute to the understanding of the transcriptome related to the Persea americana-Phytophthora cinnamomi interaction.  This study is the first assessment of the Phytophthora cinnamomi-avocado interaction on a transcriptome-wide level and adds to the limited information on the interaction between a hemibiotrophic root pathogen and its host.