Silicon-induced changes in antifungal phenolic acids, flavonoids, and key phenylpropanoid pathway genes during the interaction between miniature roses and the biotrophic pathogen Podosphaera pannosa.
Application of 3.6 mm silicon (Si+) to the rose (Rosa hybrida) cultivar Smart increased the concentration of antimicrobial phenolic acids and flavonoids in response to infection by rose powdery mildew (Podosphaera pannosa). Simultaneously, the expression of genes coding for key enzymes in the phenylpropanoid pathway (phenylalanine ammonia lyase, cinnamyl alcohol dehydrogenase, and chalcone synthase) was up-regulated. The increase in phenolic compounds correlated with a 46% reduction in disease severity compared with inoculated leaves without Si application (Si-). Furthermore, Si application without pathogen inoculation induced gene expression and primed the accumulation of several phenolics compared with the uninoculated Si- control. Chlorogenic acid was the phenolic acid detected in the highest concentration, with an increase of more than 80% in Si+ inoculated compared with Si- uninoculated plants. Among the quantified flavonoids, rutin and quercitrin were detected in the highest concentrations, and the rutin concentration increased more than 20-fold in Si+ inoculated compared with Si- uninoculated plants. Both rutin and chlorogenic acid had antimicrobial effects on P. pannosa, evidenced by reduced conidial germination and appressorium formation of the pathogen, both after spray application and infiltration into leaves. The application of rutin and chlorogenic acid reduced powdery mildew severity by 40% to 50%, and observation of an effect after leaf infiltration indicated that these two phenolics can be transported to the epidermal surface. In conclusion, we provide evidence that Si plays an active role in disease reduction in rose by inducing the production of antifungal phenolic metabolites as a response to powdery mildew infection.
Department of Plant Biology and Biotechnology, Faculty of Life Sciences, University of Copenhagen, DK-1871 Frederiksberg C, Denmark. rsh@life.ku.dk
Radhakrishna
R
Shetty
Xavier
X
Fretté
Birgit
B
Jensen
Nandini Prasad
NP
Shetty
Jens Due
JD
Jensen
Hans Jørgen Lyngs
HJ
Jørgensen
Mari-Anne
MA
Newman
Lars Porskjær
LP
Christensen
D000217:Acyltransferases / Q000235:genetics; D000429:Alcohol Oxidoreductases / Q000235:genetics; D000935:Antifungal Agents / Q000378:metabolism* / Q000494:pharmacology; D001203:Ascomycota / Q000187:drug effects / Q000502:physiology; D002726:Chlorogenic Acid / Q000378:metabolism / Q000494:pharmacology; D005419:Flavonoids / Q000378:metabolism* / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D054884:Host-Pathogen Interactions; D062385:Hydroxybenzoates / Q000378:metabolism* / Q000494:pharmacology; D010650:Phenylalanine Ammonia-Lyase / Q000235:genetics; D010935:Plant Diseases / Q000382:microbiology / Q000517:prevention & control*; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D011794:Quercetin / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D027826:Rosa / Q000187:drug effects* / Q000378:metabolism / Q000382:microbiology; D012431:Rutin / Q000378:metabolism / Q000494:pharmacology; D012825:Silicon / Q000494:pharmacology*; D015854:Up-Regulation
D000935:Antifungal Agents; D005419:Flavonoids; D062385:Hydroxybenzoates; C012526:quercitrin; D002726:Chlorogenic Acid; D012431:Rutin; D011794:Quercetin; D000429:Alcohol Oxidoreductases; C018656:cinnamyl alcohol dehydrogenase; D000217:Acyltransferases; C020141:flavanone synthetase; D010650:Phenylalanine Ammonia-Lyase; C017616:phenolic acid; D012825:Silicon