Flavonoid biosynthesis in Dianthus caryophyllus L. is early regulated during interaction with Fusarium oxysporum f. sp. dianthi.

Rooted cuttings from two carnation (Dianthus caryophyllus L.) cultivars showing contrasting responses to the vascular wilt caused by Fusarium oxysporum f. sp. dianthi (Fod) were inoculated with this phytopathogen, and some of the biochemical responses associated with flavonoid biosynthesis were investigated in the roots. The resistant cultivar ('Golem') showed a significant increase in the levels of phenolic and flavonoid compounds at 48-96 h post-inoculation (hpi) (α = 0.05). LC-MS-based analysis indicated that the flavonoids mainly included flavanol-type glycosides, especially quercetin and kaempferol aglycones. Quantification of the mRNA levels of genes encoding CHS (Chalcone Synthase), CHI (Chalcone Isomerase), FLS (Flavonol Synthase), and the transcription factor MYB11 by using reverse transcription quantitative polymerase chain reaction (RT-qPCR) indicated that the resistant cultivar exhibited higher expression levels of these genes and, therefore, showed more flavonoid accumulation at 96 hpi. The differences in the temporal regulation of the assessed variables during infection support the idea that the early expression of enzymes of the flavonoid biosynthesis pathway in carnation roots is linked to a resistance response to the hemibiotrophic pathogen Fod race 2. The present experimental approach is the first report describing the molecular mechanisms underlying flavonoid biosynthesis in carnation roots during their interaction with Fod.

Glucosinolate composition of Colombian accessions of mashua (Tropaeolum tuberosum Ruíz & Pavón), structural elucidation of the predominant glucosinolate and assessment of its antifungal activity.

BACKGROUND: The content of individual and total glucosinolates in 65 mashua tuber accessions (Tropaeolum tuberosum) from the germplasm bank at Universidad Nacional de Colombia was determined by reverse phase high-performance liquid chromatography on enzymatically desulfated extracts. The predominant glucosinolate was identified and the possible structure of the glucosinolate present in lower proportion was postulated from evidence obtained by high-performance liquid chromatography/mass spectrometry, 1 H and 13 C nuclear magnetic resonance and bi-dimensional experiments. The biological action of the hydrolysis products generated from the glucosinolates in the accessions that showed a higher content of these compounds was assessed in the presence of Fusarium oxysporum f. sp. dianthi, Rhizoctonia solani and Phytophthora infestans. RESULTS: The total content of glucosinolates ranged between >3.00 × 10-1 and 25.8 µmol g-1 dry matter. p-Methoxybenzyl glucosinolate was identified as the predominant glucosinolate in Colombian mashua accessions; besides, the possible presence of p-hydroxybenzyl glucosinolate was postulated. In vitro assays established an important fungal growth inhibition of the potato pathogen P. infestans. CONCLUSION: The biological action from p-methoxybenzyl glucosinolate and p-hydroxybenzyl glucosinolate found in Colombian mashua accessions depends on their concentration, with the Tt30 accession, characterized for showing the highest content of glucosinolates, being the most promising to control the assessed pathogens. © 2016 Society of Chemical Industry.

Protein extraction and gel-based separation methods to analyze responses to pathogens in carnation (Dianthus caryophyllus L).

We are currently using a 2-DE-based proteomics approach to study plant responses to pathogenic fungi by using the carnation (Dianthus caryophyllus L)-Fusarium oxysporum f. sp. dianthi pathosystem. It is clear that the protocols for the first stages of a standard proteomics workflow must be optimized to each biological system and objectives of the research. The optimization procedure for the extraction and separation of proteins by 1-DE and 2-DE in the indicated system is reported. This strategy can be extrapolated to other plant-pathogen interaction systems in order to perform an evaluation of the changes in the host protein profile caused by the pathogen and to identify proteins which, at early stages, are involved or implicated in the plant defense response.