Effects of Phytophthora infestans and glucan effectors on the accumulation of secondary metabolites and transcrips of defense related genes in potato.

HENRIQUEZ M. A.; WOLSKY E.A.; MOLINA O.; LORNE A.; ANDREU A.B; DAAYF F.

Quebec City

Congreso; XIV Congress on Molecular Plant-Microbe Interactions. Canada; 2009

Molecular Plant-Microbe Interactions Society

Plant pathogens have the ability to manipulate biochemical, physiological and morphological processes in their host plants through a diverse array of extracellular effector molecules that can either promote the infection or trigger defense responses. Both kinds of effectors are generally soluble glucans, glycoproteins or proteinaceous compounds synthesized constitutively by the fungal pathogen and present in the cultures filtrates. Potato susceptibility to P. infestans  has been suggested as an outcome to potato defense suppression by P. infestans glucans released only by compatible races of the oomycete under in vitro conditions. Understanding the mechanisms governing the defense and counter-defense during the potato- P. infestans in vivo interaction, will be a good step towards durable potato resistance to late blight.To analyze in a whole plant (in vivo), the effects of glucans extracted from P. infestans, the elicitor eicosapentanoic acid (EPA) and P. infestans isolates on the accumulation of secondary compounds and defense related transcripts in potato cultivars. Our results suggest a relationship between the disease level, the phenylpropanoid pathway gene expression and the accumulation of some secondary metabolites. The HPLC profiles from the analysis both RB and DF inoculated US8, showed a significant reduction of several secondary metabolites, compared with the controls (RB+H2O and DF+H20). Contrary to the US8 related treatments; the low aggressive isolate (US11) showed a lower number and size of late blight lesions and no significant reduction of secondary metabolites accumulation compared with the control (RB+H2O), In RB and DF we identified the secondary metabolites, Chlorogenic Acid, Tannic Acid, Rutin, 4-ME-Umbelliferone and p-coumaroyltyramine RB plants treated with the high aggressive isolate US8, RB plants treated with glucans and then infected with US8 (RB+GL+US8), RB plants treated with EPA and then infected with US8 (RB+EPA+US8) and RB plants pre-treated with EPA, glucan, and inoculated with US8 (RB+EPA+GL+US8) showed a suppression in the accumulation of Rutin and Chlorogenic acid. The Phenylpropanoid related genes; Phenylalanine ammonia-lyase (PAL-1 and PAL-2) 4-coumarate:CoA ligase (4CL) and Chalcone synthase (CHS) showed variation in transcripts accumulation in the 24 treatments. The current findings imply that genetic resistance in potato against P. infestans is the combination of different factors that suggest a polygenic trait or horizontal resistance. - This is the first report using a whole plant (in vivo) to study the effect of glucans and the elicitor eicosapentanoic acid (EPA) in potato cultivar  -The suppression of PAL-2, CHS and 4CL genes in Russet Burbank by P. infestans isolate US8 resulted in reduced accumulation of important secondary metabolites, thus leading to greater disease symptoms in RB+US8. - There is a synergistic effect of EPA and glucan, that produces a significant decrease of secondary metabolites and Phenylpropanoid genes transcripts.