Construction Of CDNA Library Of Arabidopsis Thaliana Infected With Phytophthora Paracitica And Analysis Of EST Sequences

Phytophthora parasitica, also known as Phytophthora nicotianae, represents a large group of plant pathogens called oomycetes, and is a soilborne pathogen capable of infecting a wide range of host plants causing huge economic losses. The effectiveness of current disease control measures against oomycetes is limited because of limited number of resistance genes. Investigation on the interaction between pathogen and the host plant at the molecular level will aid a better understanding on the pathogenesis, virulence and genetic variation in the pathogen, and subsequent development of novel disease control measures against oomycete pathogens.Plant–oomycete interactions involve exchanges of a range of molecules including pathogen effectors that play vital roles in the outcome of interaction. Pathogens secret a large number of effectors that make the host plants more susceptible by manipulating plant cell function. A large group of effectors carry a conserved motif and called RXLR was encoded by a gene family with hundreds of highly divergent members. The RXLR effectors are capable entering into host plant cells and function as virulence factors when the cognate R genes are absent or avirulence factors when being recognized by cognate plant resistance proteins.For better understanding pathogenesis of Phytophhtora, the development of a model plant-pathogen system is critical, and EST sequencing can provide large quantity of information for gene discovery. In this study, a high quality cDNA library using mRNAs derived from Arabidopsis thaliana leaves infected with P. parasitica at the early stage of infection was constructed. Library sequencing generated 3021 EST sequences of which 25.3% were of P. parasitica origin. 652 ESTs are unigenes. Several candidate RXLR effector genes were identified. Gene expression and comparative gene profiling analysis showed that the genes involved in host plant defense are dramatically up-regulated and genes responsive specifically to P. parasitica infection were identified. The results further confirmed our developed compatible A. thaliana- P. parasitica interaction.