Fungal plant pathogens secrete effector molecules to establish disease on their hosts, and plants in turn use immune receptors to try to intercept these effectors. The tomato immune receptor Ve1 governs resistance to race 1 strains of the soil-borne vascular wilt fungi Verticillium dahliae and Verticillium albo-atrum , but the corresponding Verticillium effector remained unknown thus far. By high-throughput population genome sequencing, a single 50-Kb sequence stretch was identified that only occurs in race 1 strains, and subsequent transcriptome sequencing of Verticillium -infected Nicotiana benthamiana plants revealed only a single highly expressed ORF in this region, designated Ave1 (for A virulence on Ve1 tomato ). Functional analyses confirmed that Ave1 activates Ve1-mediated resistance and demonstrated that Ave1 markedly contributes to fungal virulence, not only on tomato but also on Arabidopsis . Interestingly, Ave1 is homologous to a widespread family of plant natriuretic peptides. Besides plants, homologous proteins were only found in the bacterial plant pathogen Xanthomonas axonopodis and the plant pathogenic fungi Colletotrichum higginsianum , Cercospora beticola , and Fusarium oxysporum f. sp. lycopersici . The distribution of Ave1 homologs, coincident with the presence of Ave1 within a flexible genomic region, strongly suggests that Verticillium acquired Ave1 from plants through horizontal gene transfer. Remarkably, by transient expression we show that also the Ave1 homologs from F. oxysporum and C. beticola can activate Ve1 -mediated resistance. In line with this observation, Ve1 was found to mediate resistance toward F. oxysporum in tomato, showing that this immune receptor is involved in resistance against multiple fungal pathogens.

Vascular wilt diseases caused by soil-borne pathogens are among the most devastating plant diseases worldwide. The Verticillium genus includes vascular wilt pathogens with a wide host range. Although V. longisporum infects various hosts belonging to the Cruciferaceae, V. dahliae and V. albo-atrum cause vascular wilt diseases in over 200 dicotyledonous species, including economically important crops. A locus responsible for resistance against race 1 strains of V. dahliae and V. albo-atrum has been cloned from tomato (Solanum lycopersicum) only. This locus, known as Ve, comprises two closely linked inversely oriented genes, Ve1 and Ve2, that encode cell surface receptor proteins of the extracellular leucine-rich repeat receptor-like protein class of disease resistance proteins. Here, we show that Ve1, but not Ve2, provides resistance in tomato against race 1 strains of V. dahliae and V. albo-atrum and not against race 2 strains. Using virus-induced gene silencing in tomato, the signaling cascade downstream of Ve1 is shown to require both EDS1 and NDR1. In addition, NRC1, ACIF, MEK2, and SERK3/BAK1 also act as positive regulators of Ve1 in tomato. In conclusion, Ve1-mediated resistance signaling only partially overlaps with signaling mediated by Cf proteins, type members of the receptor-like protein class of resistance proteins.

The plant immune system is activated by microbial patterns that are detected as nonself molecules. Such patterns are recognized by immune receptors that are cytoplasmic or localized at the plasma membrane. Cell surface receptors are represented by receptor-like kinases (RLKs) that frequently contain extracellular leucine-rich repeats and an intracellular kinase domain for activation of downstream signaling, as well as receptor-like proteins (RLPs) that lack this signaling domain. It is therefore hypothesized that RLKs are required for RLPs to activate downstream signaling. The RLPs Cf-4 and Ve1 of tomato ( Solanum lycopersicum ) mediate resistance to the fungal pathogens Cladosporium fulvum and Verticillium dahliae , respectively. Despite their importance, the mechanism by which these immune receptors mediate downstream signaling upon recognition of their matching ligand, Avr4 and Ave1, remained enigmatic. Here we show that the tomato ortholog of the Arabidopsis thaliana RLK Suppressor Of BIR1-1/Evershed (SOBIR1/EVR) and its close homolog S. lycopersicum ( Sl )SOBIR1-like interact in planta with both Cf-4 and Ve1 and are required for the Cf-4– and Ve1-mediated hypersensitive response and immunity. Tomato SOBIR1/EVR interacts with most of the tested RLPs, but not with the RLKs FLS2, SERK1, SERK3a, BAK1, and CLV1. SOBIR1/EVR is required for stability of the Cf-4 and Ve1 receptors, supporting our observation that these RLPs are present in a complex with SOBIR1/EVR in planta . We show that SOBIR1/EVR is essential for RLP-mediated immunity and propose that the protein functions as a regulatory RLK of this type of cell-surface receptors.

Nanoparticles (NPs) have great potential for use in the fields of biomedicine, building materials, and environmental protection because of their antibacterial properties. However, there are few reports regarding the antifungal activities of NPs on plants. In this study, we evaluated the antifungal roles of NPs against Botrytis cinerea, which is a notorious worldwide fungal pathogen. Three common carbon nanomaterials, multi-walled carbon nanotubes, fullerene, and reduced graphene oxide, and three commercial metal oxidant NPs, copper oxide nanoparticles (CuO NPs), ferric oxide nanoparticles (Fe2O3 NPs), and titanium oxides nanoparticles (TiO2 NPs), were independently added to water-agar plates at 50-mg/L and 200-mg/L concentrations. Detached rose petals were inoculated with spores of B. cinerea and co-cultured with each of the six nanomaterials. The sizes of the lesions on infected rose petals were measured at 72 h after inoculation, and the growth of fungi on the rose petals was observed by scanning electron microscopy. The six NPs inhibited the growth of B. cinerea, but different concentrations had different effects: 50 mg/L of fullerene and CuO NPs showed the strongest antifungal properties among the treatments, while 200 mg/L of CuO and Fe2O3 showed no significant antifungal activities. Thus, NPs may have antifungal activities that prevent B. cinerea infections in plants, and they could be used as antifungal agents during the growth and post-harvesting of roses and other flowers. To the authors’ best knowledge, this is the first in planta assay illustrating the antimicrobial activities of NPs against a fungal pathogen.

Plants are exposed to a suite of herbivorous attackers that often arrive sequentially. Herbivory affects interactions between the host plants and subsequently attacking herbivores. Moreover, plants may respond to herbivory by emitting volatile organic compounds (VOCs) that attract carnivorous natural enemies of the herbivores. However, information borne by VOCs is ubiquitous and may attract carnivores, such as parasitoids, that differ in their effectiveness at releasing the plant from its herbivorous attackers. Furthermore, the development of parasitoids within their herbivorous hosts, attacking a given host plant, may influence the elicitation of defensive reactions in the host plant. This may, in turn, affect the behavior of subsequent herbivores attacking the host plant. Here, we show that the species identity of a parasitoid had a more significant effect on defense responses ofBrassica oleraceaplants than the species identity of the herbivorous hosts of the parasitoids. Consequently,B. oleraceaplants that were damaged by caterpillars (Pierisspp.) parasitized by different parasitoid species varied in the degree to which diamondback moths (Plutella xylostella) selected the plants for oviposition. Attracting parasitoids in general benefitted the plants by reducing diamondback moth colonization. However, the species of parasitoid that parasitized the herbivore significantly affected the magnitude of this benefit by its species-specific effect on herbivore–plant interactions mediated by caterpillar regurgitant. Our findings show that information-mediated indirect defense may lead to unpredictable consequences for plants when considering trait-mediated effects of parasitized caterpillars on the host plant and their consequences because of community-wide responses to induced plants.