Analysis of a suppressive subtractive hybridization library of Alternaria alternata resistant to 2-propenyl isothiocyanate

Abstract

Background: Isothiocyanates (ITCs) are natural products obtained from plants of the Brassicas family. They represent an environmentally friendly alternative for the control of phytopathogenic fungi. However, as it has been observed with synthetic fungicides, the possibility of inducing ITC-resistant strains is a major concern. It is, therefore, essential to understanding the molecular mechanisms of fungal resistance to ITCs. We analyzed a subtractive library containing 180 clones of an Alternaria alternata strain resistant to 2-propenyl ITC (2-pITC). After their sequencing, 141 expressed sequence tags (ESTs) were identified using the BlastX algorithm. The sequence assembly was carried out using CAP3 software; the functional annotation and metabolic pathways identification were performed using the Blast2GO program. Results: The bioinformatics analysis revealed 124 reads with similarities to proteins involved in transcriptional control, defense and stress pathways, cell wall integrity maintenance, detoxification, organization and cytoskeleton destabilization; exocytosis, transport, DNA damage control, ribosome maintenance, and RNA processing. In addition, transcripts corresponding to enzymes as oxidoreductases, transferases, hydrolases, lyases, and ligases, were detected. Degradation pathways for styrene, aminobenzoate, and toluene were induced, as well as the biosynthesis of phenylpropanoid and several types of N-glycan. Conclusions: The fungal response showed that natural compounds could induce tolerance/resistance mechanisms in organisms in the same manner as synthetic chemical products. The response of A. alternata to the toxicity of 2-pITC is a sophisticated phenomenon including the induction of signaling cascades targeting a broad set of cellular processes. Whole-transcriptome approaches are needed to elucidate completely the fungal response to 2-pITC.

Effects of Glucosinolate-Derived Isothiocyanates on Fungi: A Comprehensive Review on Direct Effects, Mechanisms, Structure-Activity Relationship Data and Possible Agricultural Applications

“…The strain’s ability to grow was restored from complete inhibition to 80–85% growth speed at the highest allyl ITC dosage, accompanied by induction of glutathione S-transferase-like genes, and a 2-fold increase in glutathione S-transferase catalytic activity, suggesting a specific detoxification mechanism. An interesting study of the transcriptome of an allyl ITC-resistant Alternaria alternata strain by [ 131 ] has concluded that allyl ITC can induce tolerance/resistance mechanisms in the same manner as synthetic fungicides. Induced genes coding similar-to-known proteins included many proteins and enzymes involved in the activation of signal cascades promoting cell repair and maintenance, the overexpression of which result in generic resistance-like traits.…”

Identification of Two Myrosinases from a Leclercia adecarboxylata Strain and Investigation of Its Tolerance Mechanism to Glucosinolate Hydrolysate

“…ITCs readily attack thiols and amines, consequently modifying proteins and disrupting biochemical processes, which play an important role in the defense mechanisms of GSL-containing plants against infectious microorganisms or predators . Some organisms developed tolerance mechanisms during evolution to adapt to stress; for example, some pathogens that colonize plants of the order Brassicales possess tolerance to ITC toxicity; of note, the ability to detoxify ITCs via ITC hydrolases, the glutathione conjugation pathway, or active efflux has been discovered in these organisms. − Myrosinase-producing organisms can actively release ITCs from GSLs and, therefore, should possess the mechanism(s) to tolerate the ITCs generated. However, tolerance of the strains to ITCs has not been well investigated.…”

Pollen beetle offspring is more parasitized under moderate nitrogen fertilization of oilseed rape due to more attractive volatile signal

“…In actively growing plants, high N availability speeds up primary metabolism and plant growth, while in plants with arrested growth improved nutrition can enhance storage and secondary metabolism 16 , 17 . Nitrogen is needed for the biosynthesis of glucosinolates (GLS), the anti-herbivore toxins found in the Brassica family, and their volatile derivatives isothiocyanates (emitted after tissue damage) mediate plant–insect interactions 18 – 20 . Since specialist herbivores can orient towards GLS 21 , high N in crops can even benefit pests 22 – 25 .…”