Some alternative control strategies of currently emerging plant diseases are based on the use of resistance inducers. This review highlights the recent advances made in the characterization of natural compounds that induce resistance by a priming mechanism. These include vitamins, chitosans, oligogalacturonides, volatile organic compounds, azelaic and pipecolic acid, among others. Overall, other than providing novel disease control strategies that meet environmental regulations, natural priming agents are valuable tools to help unravel the complex mechanisms underlying the induced resistance (IR) phenomenon. The data presented in this review reflect the novel contributions made from studying these natural plant inducers, with special emphasis placed on hexanoic acid (Hx), proposed herein as a model tool for this research field. Hx is a potent natural priming agent of proven efficiency in a wide range of host plants and pathogens. It can early activate broad-spectrum defenses by inducing callose deposition and the salicylic acid (SA) and jasmonic acid (JA) pathways. Later it can prime pathogen-specific responses according to the pathogen's lifestyle. Interestingly, Hx primes redox-related genes to produce an anti-oxidant protective effect, which might be critical for limiting the infection of necrotrophs. Our Hx-IR findings also strongly suggest that it is an attractive tool for the molecular characterization of the plant alarmed state, with the added advantage of it being a natural compound.

Registro de acceso restringido Este recurso no está disponible en acceso abierto por política de la editorial. No obstante, se puede acceder al texto completo desde la Universitat Jaume I o si el usuario cuenta con suscripción. Registre d'accés restringit Aquest recurs no està disponible en accés obert per política de l'editorial. No obstant això, es pot accedir al text complet des de la Universitat Jaume I o si l'usuari compta amb subscripció. Restricted access item This item isn't open access because of publisher's policy. The full--text version is only available from Jaume I University or if the user has a running suscription to the publisher's contents.

SummaryCel1 and Cel2 are members of the tomato (Solanum lycopersicum Mill) endo-b-1,4-glucanase (EGase) family that may play a role in fruit ripening and organ abscission. This work demonstrates that Cel1 protein is present in other vegetative tissues and accumulates during leaf development. We recently reported the downregulation of both the Cel1 mRNA and protein upon fungal infection, suggesting the involvement of EGases in plant-pathogen interactions. This hypothesis was confirmed by assessing the resistance to Botrytis cinerea infection of transgenic plants expressing both genes in an antisense orientation (Anti-Cel1, Anti-Cel2 and AntiCel1-Cel2). The Anti-Cel1-Cel2 plants showed enhanced resistance to this fungal necrotroph. Microscopical analysis of infected leaves revealed that tomato plants accumulated pathogen-inducible callose within the expanding lesion. Anti-Cel1-Cel2 plants presented a faster and enhanced callose accumulation against B. cinerea than wild-type plants. The inhibitor 2-deoxy-D-glucose, a callose synthesis inhibitor, showed a direct relationship between faster callose accumulation and enhanced resistance to B. cinerea. EGase activity appears to negatively modulate callose deposition. The absence of both EGase genes was associated with changes in the expression of the pathogen-related genes PR1 and LoxD. Interestingly, Anti-Cel1-Cel2 plants were more susceptible to Pseudomonas syringae, displaying severe disease symptoms and enhanced bacterial growth relative to wild-type plants. Analysis of the involvement of Cel1 and Cel2 in the susceptibility to B. cinerea in fruits was done with the ripening-impaired mutants Never ripe (Nr) and Ripening inhibitor (rin). The data reported in this work support the idea that enzymes involved in cell wall metabolism play a role in susceptibility to pathogens.

Registro de acceso restringido Este recurso no está disponible en acceso abierto por política de la editorial. No obstante, se puede acceder al texto completo desde la Universitat Jaume I o si el usuario cuenta con suscripción. Registre d'accés restringit Aquest recurs no està disponible en accés obert per política de l'editorial. No obstant això, es pot accedir al text complet des de la Universitat Jaume I o si l'usuari compta amb subscripció. Restricted access item This item isn't open access because of publisher's policy. The full--text version is only available from Jaume I University or if the user has a running suscription to the publisher's contents.