Albugo-imposed immunosuppression by compromised salicylate-triggered immunity and altered tryptophan-derived anti-microbial metabolite biosynthesis and bioavailability. Arabidopsis thaliana

Infection by Albugo species, resulting in white rust disease, suppresses host plant immunity, and can even enable Albugo laibachii-infected Arabidopsis to support growth and reproduction of the non-host potato late blight pathogen Phytophthora infestans. However, the mechanisms involved in non-host resistance remain to be elucidated. Here, we investigate specific host defense mechanisms that are suppressed by A. laibachii and A. candida infection, and compare the resistance contributed by indole glucosinolates and camalexin to that resulting from other components of defense induced by salicylic acid. We conclude a broad repertoire of host defense components contributes to non-host resistance in Arabidopsis to P. infestans, with a particular role for tryptophan-derived anti-microbial metabolites. Identifying the mechanisms involved in non-host resistance to pathogens such as P. infestans is necessary in the development of strategies to ensure future food security. Overall design: 4-5 weeks old Arabidopsis (MAGIC-107: a multi-parent recombinant inbred line) plants were spray inoculated with either Mock or Albugo candida strain Nc2 or Albugo laibachii strain Nc14 , and infected plants were harvested at 0, 2, 4, 6 and 8 days post-inoculation (dpi) for total RNA extraction. mRNA profiles were generated by deep sequencing on Illumina GAIIx using EXPRSS tag-seq protocol. Four biological replicates were collected. Samples of Nc2 and Nc14 infections from 2, 4, 6 and 8 dpi were sequenced each in a separate lane. Samples of 2 and 4 dpi are sequenced 3 times and 6 dpi samples are 2 times to generate higher depth of sequencing data. Samples of Mock, Nc2 and Nc14 infections from 0 dpi were sequenced in one lane. Mock samples from 2, 4, 6 and 8 dpi were sequenced in one lane.