Phytophthora capsici is a highly destructive pathogen of crops. Although chemical pesticides are the most widely used strategy to counter phytopathogens, they have been inefficient to combat P. capsici and have produced significant environmental and health problems. Therefore, sustainable alternatives to control soilborne pathogens, such as the inhibitory effect of self‐extracellular DNA (eDNA), have been proposed. This inhibition phenomenon has been attributed to the action of self‐eDNA as a damage‐associated molecular pattern (DAMP). Here, we describe the effect of self‐eDNA on P. capsici zoospore germination rate, antioxidant enzymes activity and MAPK gene expression. Also, the effect of P. capsici eDNA on the protection of chilli pepper (Capsicum annuum) plants against P. capsici was investigated. The results highlight that P. capsici can sense 2–500 µg/ml self‐eDNA and induce stress‐related responses like SAK1 gene expression, and superoxide dismutase and catalase activities. Moreover, in vitro zoospore germination rate was suppressed with self‐eDNA concentrations ranging from 50 to 500 µg/ml. Interestingly, drench applications of P. capsici eDNA at 60 and 100 µg/ml on chilli pepper plants did not show any protective effect against the phytopathogen, whereas 2 µg/ml of P. capsici eDNA drench application showed a lower percentage of plants with symptoms and lower disease severity. Moreover, phenols and total flavonoids were increased in chilli pepper plants, therefore inducing plant immunity. This study showed that self‐eDNA acts as a DAMP in P. capsici and provides insight into the use of eDNA for the protection of crops of agronomic interest.

Acclimation of plants to water deficit involves biochemical and physiological adjustments. Here, we studied how ultraviolet (UV)-B exposure and exogenously applied hydrogen peroxide (H 2 O 2 ) potentiates drought tolerance in tobacco (Nicotiana tabacum L. cv. xanthi nc). Separate and combined applications for 14 days of 1.75 kJ m À2 day À1 UV-B radiation and 0.2 mM H 2 O 2 were assessed. Both factors, individually and combined, resulted in inhibition of growth. Furthermore, the combined treatment led to the most compacted plants. UV-B-and UV-B + H 2 O 2 -treated plants increased total antioxidant capacity and foliar epidermal flavonol index. H 2 O 2and UV-B + H 2 O 2 -pre-treated plants showed cross-tolerance to a subsequent 7-day moderate drought treatment, which was assessed as the absence of negative impact on growth, leaf wilting, and leaf relative water content. Plant responses to the pretreatment were notably different: (1) H 2 O 2 increased the activity of catalase (EC 1.11.1.6), phenylalanine ammonia lyase (EC 4.3.1.5), and peroxidase activities (EC 1.11.1.7), and (2) the combined treatment induced epidermal flavonols which were key to drought tolerance. We report synergistic effects of UV-B and H 2 O 2 on transcription accumulation of UV RESISTANCE LOCUS 8, NAC DOMAIN PROTEIN 13 (NAC13), and BRI1-EMS-SUPPRESSOR 1 (BES1). Our data demonstrate a pre-treatment-dependent response to drought for NAC13, BES1, and CHALCONE SYNTHASE transcript accumulation. This study highlights the potential of combining UV-B and H 2 O 2 to improve drought tolerance which could become a useful tool to reduce water use. | INTRODUCTIONExtreme weather events limit plant production, which, in turn, may affect agricultural important plant species resulting in reduced food production. In addition, the frequency of such extreme events is likely to increase as climate change worsens (Lesk et al., 2016). Therefore, plant drought tolerance is an important trait for which we need to develop a more complete understanding at the physiological and molecular level (Godfray et al., 2010). Drought stress diminishes crop growth, disturbs plant water and plant nutrient relations, reduces photosynthesis, and causes oxidative damage due to the generation of reactive oxygen species (ROS) (Salehi-Lisar and Bakhshayeshan-

Transgenic tobacco (N. tabacum cv. Xanthi nc) expressing Capsicum chinense CchGLP gene that encodes an Mn-SOD, constitutively produces hydrogen peroxide that increase endogenous ROS levels. Previous studies using these plants against geminivirus infections as well as drought stress confirmed that CchGLP expression conferred resistance against biotic and abiotic stresses. Cadmium (Cd) and Aluminium (Al) contamination in soils are a major ecological concern since they are two of the most widespread toxic elements in terrestrial environments. Trying to explore additional possible tolerance to another stresses in these plants, the aim of this work was to analyse the response to cadmium and aluminium salts during germination and early stages of plantlet development and a differential transcriptome of microRNAs (miRNAs) expression in expressing CchGLP transgenic lines and an azygote non-CchGLP expressing line. Plants were grown in vitro with addition of CdCl 2 and AlCl 3 at three different concentrations: 100, 300 and 500 lM and 50, 150 and 300 lM, respectively. The results showed higher tolerance to Cd and Al salts evaluated in two CchGLP-expressing transgenic lines L8 and L26 in comparison with the azygous non-CchGLP expressing line L1. Interestingly, L8 under Al stress presented vigorous roots and development of radicular hairs in comparison with azygous control (L1). Differentially expressed miRNAs in the comparison between L8 and L1 were associated with up and downregulation of target genes related with structural molecule activity and ribosome constituents, as well as down-regulation in proton-transporting V-type ATPase (Vacuolar ATPase or V-ATPase). Moreover, KEGG analysis of the target genes for the differentially expressed miRNAs, led to identification of genes related with metabolic pathways and biosynthesis of secondary metabolites. One possible explanation of the tolerance to Cd and Al displayed in the transgenic tobaccos evaluated, might involve the fact that several down-regulated miRNAs, were found associated with target genes expressing V-ATPase. Specifically, miR7904-5p was down regulated and related with the upregulation of one V-ATPase. The expression levels of these genes was confirmed by qRT-PCR assays, thus suggesting that a cation transport activity driven by the V-ATPasesdependent proton motive force, might significantly contribute as one mechanism for Cd and Al detoxification by vacuolar compartmentation in these transgenic tobacco plants.

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