Inhibition of Virulence-Related Traits in Pseudomonas syringae pv. actinidiae by Gunpowder Green Tea Extracts

Green tea is a widely-consumed healthy drink produced from the leaves of Camellia sinensis. It is renowned for its antioxidant and anticarcinogenic properties, but also displays significant antimicrobial activity against numerous human pathogens. Here we analyzed the antimicrobial activity of Gunpowder green tea against Pseudomonas syringae pv. actinidiae (Psa), the agent that causes kiwifruit bacterial canker. At the phenotypic level, tea extracts strongly inhibited Psa growth and swimming motility, suggesting it could reduce Psa epiphytic survival during plant colonization. The loss of bacterial virulence-related traits following treatment with tea extracts was also investigated by large-scale transcriptome analysis, which confirmed the in vitro phenotypes and revealed the induction of adaptive responses in the treated bacteria allowing them to cope with iron deficiency and oxidative stress. Such molecular changes may account for the ability of Gunpowder green tea to protect kiwifruit against Psa infection

Plant and fungus transcriptomic data from grapevine berries undergoing artificially-induced noble rot caused by Botrytis cinerea

Noble rot is a latent infection of grape berries caused by the necrotrophic fungus Botrytis cinerea, which develops under specific climatic conditions. The infected berries undergo biochemical and metabolic changes, associated with a rapid withering, which altogether offer interesting organoleptic features to sweet white wines. In this paper, we provide RNAseq datasets (raw and normalized counts as well as differentially expressed genes lists) of the transcriptome profiles of both grapevine berries (Vitis vinifera cv. Garganega) and B. cinerea during the establishment of noble rot, artificially induced in controlled conditions. The sequencing data are available in the NCBI GEO database under accession number GSE116741. These data were exploited in a comprehensive meta-analysis of gene expression during noble rot infection, gray mold and post-harvest withering. This highlighted an important common transcriptional reprogramming in different botrytized grape berry varieties and led to the identification of key genes specifically modulated during noble rot infection, which are described in the article entitled \u201cSpecific molecular interactions between Vitis vinifera and Botrytis cinerea are required for noble rot development in grape berries\u201

From lichens to crops: Pathogenic potential of Pseudomonas syringae from Peltigera lichens is similar to worldwide epidemic strains

The presence of bacteria belonging to the Pseudomonas syringae complex in the natural vegetation of several Icelandic habitat types has been recently reported, raising questions about the risk to Icelandic crops, particularly given the expected increase in agricultural activity due to climate warming. This study takes advantage of Iceland's unique characteristics and the discovery of P. syringae in Peltigera lichens to gain a better understanding of the potential risk posed by this newly discovered ecological niche. The main objective was to evaluate the pathogenic potential and fitness in crops of P. syringae strains isolated from Peltigera lichen sampled in Iceland, focusing on strains that belong to phylogroups 1 and 2, which commonly contain epidemic strains. The results indicate that P. syringae strains isolated from Icelandic Peltigera lichen have a comparable fitness to epidemic strains in 8 out of 10 tested plant species (rice, tomato, thale cress, annual mugwort, spinach, garlic chives, tobacco and kale). Furthermore, pathogenicity assessment on three plant species highlighted that certain strains also caused similar symptoms and disease severity compared to epidemic strains. These findings provide valuable insights into the potential risks posed by P. syringae from Icelandic natural habitats and illustrate how strains from these habitats have a wide pathogenic potential to crops without having encountered these crops in the last several thousand years of their presence in Iceland

N-Acyl Homoserine Lactones and Lux Solos Regulate Social Behaviour and Virulence of Pseudomonas syringae pv. actinidiae

The phyllosphere is a complex environment where microbes communicate through signalling molecules in a system, generally known as quorum sensing (QS). One of the most common QS systems in Gram-negative proteobacteria is based on the production of N-acyl homoserine lactones (AHLs) by a LuxI synthase and their perception by a LuxR sensor. Pseudomonas syringae pv. actinidiae (Psa), the aetiological agent of the bacterial canker of kiwifruit, colonises plant phyllosphere before penetrating via wounds and natural openings. Since Psa genome encodes three LuxR solos without a cognate LuxI, this bacterium may perceive diffusible signals, but it cannot produce AHLs, displaying a non-canonical QS system. The elucidation of the mechanisms underlying the perception of environmental cues in the phyllosphere by this pathogen and their influence on the onset of pathogenesis are of crucial importance for a long-lasting and sustainable management of the bacterial canker of kiwifruit. Here, we report the ability of Psa to sense its own population density and the presence of surrounding bacteria. Moreover, we show that Psa can perceive AHLs, indicating that AHL-producing neighbouring bacteria may regulate Psa virulence in the host. Our results suggest that the ecological environment is important in determining Psa fitness and pathogenic potential. This opens new perspectives in the use of more advanced biochemical and microbiological tools for the control of bacterial canker of kiwifruit

Climate change impact on Mediterranean viticultural regions and site-specific climate risk-reduction strategies

The global increase in extreme weather and climate events may dramatically impact agriculture, food safety, and socioeconomic dynamics. The Mediterranean basin is already exposed to extreme climatic events, severely challenging viticulture, a pivotal Mediterranean agro–industry. This study aims to understand better how climate is expected to evolve in six viticulturally important Mediterranean regions in Portugal, Italy, Turkey and Morocco, using a 4–member ensemble of climatic model projections under Representative Concentration Pathways (RCP) 4.5 and 8.5 for 2041–2070, and using the 1981–2010 period as a baseline. By comparing the main specific challenges these locations will face, we comparatively define the best strategies to reduce the impacts of climate change at the national and regional levels. Projections show increases in overall temperatures, up to + 3.6°C than the historical baseline, whilst precipitation projections indicate decreases that could reach 36% of the overall annual precipitation. Biological effective degree days, consecutive dry days, growing season length, tropical nights, or very heavy precipitation days, also show challenging prospects for viticulture in these countries. A screening of the adaptative strategies already undertaken in the studied countries suggests that growers are taking reactive rather than preventive strategies. Moreover, the discussion of the most suitable strategies in this study is region–specific, i.e., prioritised by the specific needs of each location. The conclusions drawn herein may support local growers, improving their decision–making based on the most adequate adaptive strategies to their conditions, thus optimising their sustainable production under changing climates

NAC61 regulates late- and post-ripening osmotic, oxidative, and biotic stress responses in grapevine

During late- and post-ripening stages, grape berry undergoes profound biochemical and physiological changes whose molecular control is poorly understood. Here, we report the role of NAC61, a grapevine NAC transcription factor, in regulating different processes involved in berry ripening progression. NAC61 is highly expressed during post-harvest berry dehydration and its expression pattern is closely related to sugar concentration. The ectopic expression of NAC61 in Nicotiana benthamiana leaves resulted in low stomatal conductance, high leaf temperature, tissue collapse and a higher relative water content. Transcriptome analysis of grapevine leaves transiently overexpressing NAC61 and DNA affinity purification and sequencing analyses allowed us to narrow down a list of NAC61-regulated genes. Direct regulation of the stilbene synthase regulator MYB14, the osmotic stress-related gene DHN1b, the Botrytis cinerea susceptibility gene WRKY52, and NAC61 itself was validated. We also demonstrate that NAC61 interacts with NAC60, a proposed master regulator of grapevine organ maturation, in the activation of MYB14 and NAC61 expression. Overall, our findings establish NAC61 as a key player in a regulatory network that governs stilbenoid metabolism and osmotic, oxidative, and biotic stress responses that are the hallmark of late- and post-ripening grape stages.NAC61 regulates stilbene biosynthesis and abiotic/biotic stress responses that hallmark late- and post-ripening developmental stages in grapes. NAC61 self-activates and synergistically interacts with the master ripening regulator NAC60

NO signaling functions in the biotic and abiotic stress responses

In the last 1990s, NO became an increasingly popular target of investigation in plants. As in mammals, NO fulfils a broad spectrum of signalling functions in pathophysiological processes in plants. Here we summarize studies published in recent years that provide novel insights into the signalling functions of NO produced by plant cells exposed to abiotic stresses and biotic stress (pathogen-derived elicitors). Particularly, we report that NO emerges as a key messenger governing the overall control of Ca2+ homeostasis. Although the precise signalling functions of NO are poorly understood, its capacity to modulate Ca2+ homeostasis provides an extraordinary and remarkable effective way of conveying information

Genome-wide characterisation and expression profile of the grapevine ATL ubiquitin ligase family reveal biotic and abiotic stress-responsive and development-related members

The Arabidopsis T\uf3xicos en Levadura (ATL) protein family is a class of E3 ubiquitin ligases with a characteristic RING-H2 Zn-finger structure that mediates diverse physiological processes and stress responses in plants. We carried out a genome-wide survey of grapevine (Vitis vinifera L.) ATL genes and retrieved 96 sequences containing the canonical ATL RING-H2 domain. We analysed their genomic organisation, gene structure and evolution, protein domains and phylogenetic relationships. Clustering revealed several clades, as already reported in Arabidopsis thaliana and rice (Oryza sativa), with an expanded subgroup of grapevine-specific genes. Most of the grapevine ATL genes lacked introns and were scattered among the 19 chromosomes, with a high level of duplication retention. Expression profiling revealed that some ATL genes are expressed specifically during early or late development and may participate in the juvenile to mature plant transition, whereas others may play a role in pathogen and/or abiotic stress responses, making them key candidates for further functional analysis. Our data offer the first genome-wide overview and annotation of the grapevine ATL family, and provide a basis for investigating the roles of specific family members in grapevine physiology and stress responses, as well as potential biotechnological applications

Comprehensive workflow for the genome-wide identification and expression meta-analysis of the ATL E3 ubiquitin ligase gene family in grapevine

Classification and nomenclature of genes in a family can significantly contribute to the description of the diversity of encoded proteins and to the prediction of family functions based on several features, such as the presence of sequence motifs or of particular sites for post-translational modification and the expression profile of family members in different conditions. This work describes a detailed protocol for gene family characterization. Here, the procedure is applied to the characterization of the Arabidopsis Tóxicos in Levadura (ATL) E3 ubiquitin ligase family in grapevine. The methods include the genome-wide identification of family members, the characterization of gene localization, structure, and duplication, the analysis of conserved protein motifs, the prediction of protein localization and phosphorylation sites as well as gene expression profiling across the family in different datasets. Such procedure, which could be extended to further analyses depending on experimental purposes, could be applied to any gene family in any plant species for which genomic data are available, and it provides valuable information to identify interesting candidates for functional studies, giving insights into the molecular mechanisms of plant adaptation to their environment.The work was supported by the University of Verona within the frame of Joint Project 2014 (Characterization of the ATL gene family in grapevine and of its involvement in resistance to Plasmopara viticola)

Red and Blue Light Differently Influence Actinidia chinensis Performance and Its Interaction with Pseudomonas syringae pv. Actinidiae

Light composition modulates plant growth and defenses, thus influencing plant–pathogen interactions. We investigated the effects of different light-emitting diode (LED) red (R) (665 nm) and blue (B) (470 nm) light combinations on Actinidia chinensis performance by evaluating biometric parameters, chlorophyll a fluorescence, gas exchange and photosynthesis-related gene expression. Moreover, the influence of light on the infection by Pseudomonas syringae pv. actinidiae (Psa), the etiological agent of bacterial canker of kiwifruit, was investigated. Our study shows that 50%R–50%B (50R) and 25%R–75%B (25R) lead to the highest PSII efficiency and photosynthetic rate, but are the least effective in controlling the endophytic colonization of the host by Psa. Monochromatic red light severely reduced ΦPSII, ETR, Pn, TSS and photosynthesis-related genes expression, and both monochromatic lights lead to a reduction of DW and pigments content. Monochromatic blue light was the only treatment significantly reducing disease symptoms but did not reduce bacterial endophytic population. Our results suggest that monochromatic blue light reduces infection primarily by modulating Psa virulence more than host plant defenses