The interaction between Arabidopsis and the bacterial pathogen Pseudomonas syringae has been used as a model for investigating the various mechanisms and processes involved in host resistance and bacterial virulence. Most of what is known about disease resistance based on single race-specific resistance (R) genes has been elucidated by using the Arabidopsis/Pseudomonas model. The majority of R genes encode NB-LRR proteins, which help recognize specific pathogens that express a corresponding avr (avirulence) gene. The interaction between R and avr genes is based on coevolution of the interacting species. Hence, R genes provide high resistance to specific pathogens. In contrast, the main objective of this research is to look for genes that confer resistance to pathogens at a more basic level, genes that will confer resistance in host plants in a wide variety of genera to various pathogenic organisms. The approximately 20 000 rice full-length cDNA overexpressed Arabidopsis lines (rice FOX Arabidopsis lines) offer a unique opportunity to study the function of rice genes ectopically expressed in an Arabidopsis genomic background.
We hope to uncover some of the bases for the so-called non-race-specific or non-host resistance, the basic mechanism used by plants to prevent most microorganisms from becoming deadly pathogens.
To determine the possible roles of the rice cDNAs in resisting plant pathogens, we screened rice FOX Arabidopsis lines for resistance to the model pathogen P. syringae pv. tomato DC3000 (Pst). The lines were sown in 2 replications at 5 seeds per well in 60-well plates containing pre-sterilized moist black peat moss. After a 2-day cold (4 °C) exposure, the seeds were germinated and grown in aseptic condition for 3 weeks under a 9-h light - 15-h dark regime at 22 °C. The plants were dipped for 30 s in a suspension containing Pst at 0.5 to 2 x 108 cfu/mL supplemented with 0.05% Silwet 77. Plants were subsequently incubated for 3 days in the dark and then 3 days under light before evaluation of survival. Lines that had survivors, as indicated by residual green on the foliage and red fluorescence (of functional chlorophyll) under UV light, were deemed possible resistant lines. Candidate lines were re-screened 2 times for verification.