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The plant epidermis is the first line of plant defense against pathogen invasion, and likely contains important regulatory proteins related to the plant–pathogen interaction. This study aims to identify the candidates of these regulatory proteins expressed in the plant epidermis. We performed comparative proteomic studies to identify rapidly and locally expressed proteins in the leaf epidermis inoculated with fungal phytopathogen. The conidia solutions were dropped onto the Arabidopsis leaf surface, and then, we collected the epidermal tissues from inoculated and mock-treated leaves at 4 and 24 hpi. The label-free quantification methods showed that expressions of Arabidopsis proteins, which are related to defense signals, such as BAK1, MKK5, receptor-like protein kinases, transcription factors, and stomatal functions, were rapidly induced in the epidermal tissues of inoculated leaves. In contrast, most of them were not differentially regulated by fugal inoculation in the whole leaves. These findings clearly indicate that epidermal proteomics can monitor locally expressed proteins in inoculated areas of plant tissues. We also identified the 61 fungal proteins, including effector-like proteins specifically expressed on the Arabidopsis epidermis. Our new findings suggested that epidermal proteomics is useful for understanding the local expressions of plant and fungal proteins related to their interactions.

Summary In photosynthetic cells, plants convert carbon dioxide to sugars that can be moved between cellular compartments by transporters before being subsequently metabolized to support plant growth and development. Most pathogens cannot synthesize sugars directly but have evolved mechanisms to obtain plant‐derived sugars as C resource for successful infection and colonization. The availability of sugars to pathogens can determine resistance or susceptibility. Here, we summarize current progress on the roles of sugar transporters in plant–pathogen interactions. We highlight how transporters are manipulated antagonistically by both host and pathogens in competing for sugars. We examine the potential application of this target in resistance breeding and discuss opportunities and challenges for the future.

The enemy-release hypothesis (ERH) states that species become more successful in their introduced range than in their native range because they leave behind natural enemies in their native range and are thus \"“released\"” from enemy pressures in their introduced range. The ERH is popularly cited to explain the invasive properties of many species and is the underpinning of biological control. We tested the prediction that plant populations are more strongly regulated by natural enemies (herbivores and pathogens) in their native range than in their introduced range with enemy-removal experiments using pesticides. These experiments were replicated at multiple sites in both the native and invaded ranges of the grass Brachypodium sylvaticum . In support of the ERH, enemies consistently regulated populations in the native range. There were more tillers and more seeds produced in treated vs. untreated plots in the native range, and few seedlings survived in the native range. Contrary to the ERH, total measured leaf damage was similar in both ranges, though the enemies that caused it differed. There was more damage by generalist mollusks and pathogens in the native range, and more damage by generalist insect herbivores in the invaded range. Demographic analysis showed that population growth rates were lower in the native range than in the invaded range, and that sexually produced seedlings constituted a smaller fraction of the total in the native range. Our removal experiment showed that enemies regulate plant populations in their native range and suggest that generalist enemies, not just specialists, are important for population regulation.

Tree resistance can be enhanced by a variety of biotic and abiotic inducers, including nonpathogenic and pathogenic microbes, and herbivores, resulting in enhanced protection against further biotic injury. Induced resistance (IR) could be a valuable tool in sustainable pest management. IR has been actively studied in herbaceous plant species, and, in recent years, in woody plant species, and is fast emerging as an intriguing, eco-friendly concept for enhancing tree resistance. However, before application of IR becomes possible, there is a need to increase our knowledge of the mechanisms of defence in forest trees. A richer understanding of these phenomena will play a critical role in developing sustainable integrated pest management strategies. This review summarizes our current knowledge of IR in forest trees, focusing on inducible defence mechanisms, systemic induction of resistance and phytohormone signalling networks. We conclude by discussing the potential advantages and limitations of applying IR-based management tools in forest systems.

The world is rapidly urbanizing, thereby transforming natural landscapes and changing the abundance and distribution of organisms. However, insights into the effects of urbanization on species interactions, and plant-pathogen interactions in particular, are lacking. We investigated the effects of urbanization on powdery mildew infection on Quercus robur at continental and within-city scales. At the continental scale, we compared infection levels between urban and rural areas of different-sized cities in Europe, and investigated whether plant traits, climatic variables and CO 2 emissions mediated the effect of urbanization on infection levels. Within one large city (Stockholm, Sweden), we further explored whether local habitat features and spatial connectivity influenced infection levels during multiple years. At the continental scale, infection severity was consistently higher on trees in urban than rural areas, with some indication that temperature mediated this effect. Within Stockholm city, temperature had no effect, while local accumulation of leaf litter negatively affected powdery mildew incidence in one out of three years, and more connected trees had lower infection levels. This study is the first to describe the effects of urbanization on plant-pathogen interactions both within and among cities, and to uncover the potential mechanisms behind the observed patterns at each scale.

1. Evolutionary adaptations in interactions between plants, microbes and arthropods are generally studied in interactions that involve only two of these groups, that is, plants and microbes, plants and arthropods or arthropods and microbes. 2. We review the accumulating evidence from a wide variety of systems, including plant- and arthropod-associated microbes, and symbionts as well as antagonists, that selection and adaptation in seemingly two-way interactions between plants and microbes, plants and arthropods and arthropods and microbes are often driven by the biotic context of a third partner. 3. We extend the concept of local adaptation from two-way interactions to scenarios for three-way interactions. We show that consumers can locally adapt to specific host phenotypes that are induced by a third species with which they do not directly interact. This emphasizes that indirect interactions have not only ecological but also important evolutionary consequences, and stresses the need to conduct studies of local adaptation in the proper ecological context of the species involved. 4. Overall, our review underlines the importance of three-way interactions in the evolution of plant—microbe, plant—arthropod and arthropod—microbe interactions, and we outline some promising directions for future research.

Changes in cytosolic free calcium ([Ca²⁺]cyₜ) are an early and essential element of signalling networks activated by the perception of pathogen‐associated molecular patterns (PAMPs), such as flg22. The flg22‐induced calcium signal has been described on whole‐plant, but not on single‐cell scale so far. Also, the Ca²⁺ sources and channels contributing to its generation are still obscure. Ratiometric fluorescence imaging employing the calcium reporter Yellow Cameleon 3.6 was performed to analyse the flg22‐induced calcium signature in single guard cells of Arabidopsis thaliana. Calcium stores and channel types involved in its generation were determined by a pharmacological approach. In contrast to the calcium signal determined on whole‐plant level, the signature on single‐cell level is not characterized by one sustained response, but by oscillations in [Ca²⁺]cyₜ. These oscillations were abolished by EGTA and lanthanum, as well as by U73122, neomycin and TMB‐8, but only partially or not at all affected by inhibitors of glutamate receptor‐like channels and cyclic nucleotide‐gated channels. Our analyses suggest that the response observed on whole‐plant level is the summary of oscillations occurring in single cells. Parallel to external calcium, influx via channels located at internal stores contributes to the signal.

The induction of resistance to disease during plant development is widespread in the plant kingdom. Resistance appears at different stages of host development, varies with plant age or tissue maturity, may be specific or broad-spectrum and is driven by diverse mechanisms, depending on plant-pathogen interactions. Studies of these forms of resistance may help us to evaluate more exhaustively the plethora of levels of regulation during development, the variability of the defense potential of developing hosts and may have practical applications, making it possible to reduce pesticide applications. Here, we review the various types of developmental resistance in plants and current knowledge of the molecular and cellular processes involved in their expression. We discuss the implications of these studies, which provide new knowledge from the molecular to the agrosystem level. Summary 405 I. Introduction 405 II. The many forms of developmental resistance 406 III. Molecular mechanisms of developmental resistance 410 IV. Relationships between defense and development in plants 412 V. Concluding remarks 413 Acknowledgements 413 References 413

Organisms are adapted to particular habitats; consequently, community composition changes across environmental gradients, enhancing regional diversity. In Panama, a rainfall gradient correlates with the spatial turnover of tree species. While strong evidence suggests that tree species common in the wetter forests are excluded from the drier forests by seasonal drought, the factor(s) excluding drought‐tolerant species, common in the drier forests, from the wetter forests remain ambiguous. Here, we show that seedlings were significantly more likely to suffer pathogen‐caused damage and mortality in the wetter forest. While seedlings of dry‐ and wet‐forest species were equally likely to suffer pathogen attack, seedlings of dry‐forest species were significantly more likely to die when attacked and tended to suffer more pathogen‐caused mortality overall. Furthermore, seedlings of dry‐forest species suffered pathogen‐caused mortality in the forest in which they do not naturally occur and in which conspecific and/or congeneric adults are absent or rare, indicating that some pathogens are relatively widespread and/or are capable of damaging multiple host species. Synthesis. Elevated risk of pathogen‐caused damage and mortality in the wetter forests and a greater impact to host fitness from pathogen attack for seedlings of dry‐forest species suggest that pathogens may enhance regional forest diversity by contributing to changes in tree species composition via the exclusion of dry‐forest tree species from the wetter forests. This study highlights a potentially widespread and under explored mechanism by which pathogens shape plant communities at the landscape scale. An understanding of how species’ distributions are shaped by the interplay between abiotic and biotic factors is essential for conservation biology.

Rice ( ) is the leading source of nutrition for more than half of the world's population, and by far it is the most important commercial food crop. But, its growth and production are significantly hampered by the bacterial pathogen pv. (Xoo) which causes leaf blight disease. Earlier studies have reported the antibacterial ability of FDA-approved niclosamide drug against Xoo. However, the underlying mechanism by which niclosamide blocks the growth of Xoo remained elusive. In the present study, by employing the microbiological, microscopical, molecular, bioinformatics and analytical tools we found that niclosamide can directly inhibit the growth of the Xoo by hampering the biofilm formation and the production of xanthomonadin and exopolysaccharide substances (EPS) required for relentless growth and virulence of Xoo. Interestingly, niclosamide was found to specifically suppress the growth of Xoo without affecting other bacteria like . Our electron microscopic observations disclosed that niclosamide disrupts the membrane permeability of Xoo and causes the release of intracellular components. Similarly, the molecular docking analysis disclosed the molecular interaction of niclosamide with the biofilm, virulence and quorum sensing related proteins, which was further substantiated by relative gene expression analysis where niclosamide was found to significantly downregulate the expression of these key regulatory genes. In addition, considerable changes in chemical structures were detected by Fourier Transform Infrared Spectroscopy (FTIR) in response to niclosamide treatment. Overall, our findings advocate the utilization of niclosamide as a safe and potent alternative antibacterial compound to control bacterial blight disease in rice.