Abstract
The Arabidopsis thaliana SSI2 gene encodes a plastid localized stearoyl ACP desaturase. The ssi2 mutant confers dwarf morphology, spontaneously forming cell-death lesions, constitutive elevated accumulation of salicylic acid and pathogenesis related gene transcripts and enhanced resistance to oomycete, bacterial and viral pathogens. Here, to isolate a novel factor related to fatty acid metabolism signaling involved in plant defense mechanisms, we generated the rdc2 ssi2 double mutant using an EMS, which suppressed the ssi2 phenotypes containing enhanced resistance to several pathogens. The rdc2 ssi2 shows not completely recovered phenotypes, as the rdc2 ssi2 is slightly smaller than the wild-type plant. Comparison with the wild-type plant, the rdc2 single mutant generated by back-crossing with the wild-type plant had i)less amount of chlorophyll, ii)insensitivity to Paraquat which induced cell death via accumulation of reactive oxygen species (ROS), iii)more susceptibility to avirulent pathogens resulted from less accumulation of ROS. These results suggest that the RDC2 gene is related to ROS accumulation involved in defense mechanisms orchestrated by fatty acid metabolites.
