Hexanoic Acid Treatment Prevents Systemic MNSV Movement in Cucumis melo Plants by Priming Callose Deposition Correlating SA and OPDA Accumulation

Abstract

Unlike fungal and bacterial diseases, no direct method is available to control viral diseases. The use of resistance-inducing compounds can be an alternative strategy for plant viruses. Here we studied the basal response of melon to Melon necrotic spot virus (MNSV) and demonstrated the efficacy of hexanoic acid (Hx) priming, which prevents the virus from systemically spreading. We analysed callose deposition and the hormonal profile and gene expression at the whole plant level. This allowed us to determine hormonal homeostasis in the melon roots, cotyledons, hypocotyls, stems and leaves involved in basal and hexanoic acid-induced resistance (Hx-IR) to MNSV. Our data indicate important roles of salicylic acid (SA), 12-oxo-phytodienoic acid (OPDA), jasmonic-isoleucine, and ferulic acid in both responses to MNSV. The hormonal and metabolites balance, depending on the time and location associated with basal and Hx-IR, demonstrated the reprogramming of plant metabolism in MNSV-inoculated plants. The treatment with both SA and OPDA prior to virus infection significantly reduced MNSV systemic movement by inducing callose deposition. This demonstrates their relevance in Hx-IR against MNSV and a high correlation with callose deposition. Our data also provide valuable evidence to unravel priming mechanisms by natural compounds.

Chitosan primes plant defence mechanisms againstBotrytis cinerea, including expression of Avr9/Cf-9 rapidly-elicited genes

“…These results demonstrate that fungal growth arrest after chitosan treatment is not directly mediated by the toxicity effect of the chemical, as the infected leaves were formed after treatment and therefore were not sprayed with the elicitor. Moreover, these results demonstrate similar priming mechanisms after chitosan treatment to other elicitors, including Hx, which has been linked with priming of callose and JA against B. cinerea (Fernández-Crespo et al, 2017, Wang et al, 2014). Interestingly, however, despite many reported antagonistic and other crosstalk interactions between plant hormones (Robert-Seilaniantz et al, 2011), the concentrations of other plant hormones, SA and ABA, were not affected.…”

The effect of mandelonitrile, a recently described salicylic acid precursor, on peach plant response against abiotic and biotic stresses

“…On the other hand, studies on the use of chemicals to control viral diseases are scarce (Fernández‐Crespo et al . ). Different compounds have been used to prevent or reduce infection by different pathogens including plant viruses.…”

“…In a more recent work, it has been reported that hexanoic acid prevents the spread of MNSV ( Melon necrotic spot virus ) in melon plants (Fernández‐Crespo et al . ). This response was parallel to an increase in callose deposition and ferulic acid, as well as to a decrease in H 2 O 2 accumulation in the cotyledons.…”

The Type III Accessory Protein HrpE of Xanthomonas oryzae pv. oryzae Surpasses the Secretion Role, and Enhances Plant Resistance and Photosynthesis

“…The callose of rice leaves was stained on the infiltration site with aniline blue and then the samples were cytologically observed by using UV fluorescence microscopy. The leaves of rice were infiltrated with 2.0 µM of HrpE, while RFP protein served as control in this study, and the callose staining for leaves of each treatment was observed by using UV fluorescence microscopy 24 hpi as reported [30]. Image J software was used to estimate the callose intensity from digital photographs by the number of blue pixels as compared to the total number of pixels covering the leaves.…”