Soybean β‐conglycinin and catfish cutaneous mucous p22 glycoproteins deteriorate sporangial cell walls of Pseudoperonospora cubensis and suppress cucumber downy mildew

Abstract

BACKGROUND: Cucumber plants suffer from a serious threatening disease, downy mildew, throughout the growing seasons irrespective of the weather temperature. The causal agent, Pseudoperonospora cubensis, tends to evolve rapidly upon sequential applications of chemical fungicides and generate new progeny possessing tolerance to such fungicides. Glycoproteins represent an environmentally safe alternative for chemically synthetized fungicides and do not trigger fungicide resistance. We studied the antifungal activity of four glycoproteins namely soybean ⊎-conglycinin, chickpea vicilin, duck egg ovomucin and catfish p22 against P. cubensis. Ten commercial fungicides of different chemical groups were used as positive controls of glycoprotein treatments. RESULTS:The results revealed that soybean ⊎-conglycinin and catfish p22 glycoproteins possess significant antifungal activity against P. cubensis. The amount of disease suppression caused by ⊎-conglycinin and p22 was comparable to the highly efficient chemical fungicides containing copper oxychloride, cymoxanil and fosetyl Al as active ingredients. Vicilin and ovomucin were less efficient biocides as they gave moderate suppression of disease severity. However, all tested glycoproteins provided full protection for the newly emerged cucumber leaves. Microscopic examination of glycoprotein-treated leaves inferred the ability of catfish p22 and soybean ⊎-conglycinin to disrupt the integrity of sporangial cell walls of P. cubensis rendering them nonviable compared to untreated ones. Expression levels of total phenolic compounds and the antioxidant enzymes catalase, superoxide dismutase and peroxidase were elevated upon glycoproteins application, which infers their involvement in disease suppression.CONCLUSION: This report emphasizes the direct and indirect roles of glycoproteins in safe management of cucumber downy mildew disease.

In-silico Studies Calculated a New Chitin Oligomer Binding Site Inside Vicilin: A Potent Antifungal and Insecticidal Agent

“…44 Many plant vicilins from Fabaceae have been reported as antifungal agents, for example, Vigna unguiculata, Vigna aconitifolia, Vigna radiata, and Glycine max. 10,45,46 Vicilin isolated from Vigna unguiculata showed growth inhibition against Saccharomyces cerevisiae, Fusarium oxysporum, Fusarium solani, Ustilago madis, and Neurospora crassa. Similarly, another vicilin from cheese weed inhibited the growth of Fusarium graminearum and Phytophthora infestans.…”

Polyphasic Characterization of Four Aspergillus Species as Potential Biocontrol Agents for White Mold Disease of Bean

“…Spores suspension of Aspergillus spp. was prepared and adjusted to 10 6 cfu/mL −1 as previously shown [ 37 , 56 ]. Spore suspension of each fungal isolate was used for three-point inoculation on MEA (Oxoid, Basingstoke, Hampshire, England) and PDA.…”

In Silico Analysis and Functional Characterization of Antimicrobial and Insecticidal Vicilin from Moth Bean (Vigna aconitifolia (Jacq.) Marechal) Seeds

“…It is generally known that chitin found in fungal cell walls interacts with a group of proteins known as chitin binding proteins [ 20 , 53 ], causing growth inhibition in these species, as shown in [ 44 , 65 ]. These findings suggest that legume seed vicilins may interact with organisms that contain glucose, sucrose, chitin, chitin derivatives, or N -acetylglucosamine-containing glycoconjugates in structures exposed to the outside environment [ 66 ]. Some proteins, such as vicilins, which have shown chitin binding affinity, which has been attributed to their insect toxicity [ 67 ].…”