ABSTRACT: Effects of alfalfa Verticillium wilt on alfalfa plant quality and rhizosphere soil microorganisms in an experimental field of different biocontrol bacteria
Project description:Cultivated olive tree (Olea europaea L. subsp. europaea var. europaea) is one of most relevant worldwide-extended crops. Since this plant has a huge effect on the economy of several regions, especially in those located in the Mediterranean basin, all efforts focused on its protection have a great relevance in agriculture sustainability. As all extended crops, olive tree cultivars are under the threat of a wide range of pathogens. Among them, Verticillium dahliae has been in the spotlight in the last decades because the disease caused by this soil-borne fungus (Verticillium wilt) is easily spread and can eventually kill the tree. In this line, many different factors have been studied in order to shed some light on the molecular/genetic mechanisms underlying the Olea europaea-Verticillium dahliae interaction, some of them focused on the gene expression pattern of the host. In this study, the expression pattern of roots from thirty-six O. europaea cultivars with different resistance/susceptibility degree to Verticillium wilt has been analyzed by RNA-Seq. As a result, processes involved in plant defense, transcription and root development have emerged as potential players in the differential response to Verticillium wilt of these cultivars. Additionally, a quite interesting set of 421 genes with an opposite expression pattern in those cultivars showing extreme resistance/susceptibility to Verticillium wilt has been discovered, establishing a solid group of candidates to take into account in future genetic improvement programs.
Project description:Combating the action of plant pathogenic microorganisms by antagonistic or mycoparasitic fungi has been announced as an attractive biological alternative to the use of chemical fungicides since more than 20 years, and gains additional importance in current trends to environmentally friendly agriculture. Taxa of the fungal genus Hypocrea/Trichoderma (Ascomycota, Hypocreales, Hypocreaceae) contain prominent examples of such biocontrol agents, because they not only antagonize plant-pathogenic fungi, but are also often rhizosphere competent and can enhance plant growth. Identification of the primary factors that regulate the mycoparasitic behaviour and metabolic activities related to it will therefore allow the full ecological significance of this trait to be explored. We performed the analysis of the genome sequence from two mycoparasitic and rhizosphere competent Trichoderma spp. – T. atroviride and T. virens – and compare it to that of the saprophyte T. reesei. The predicted gene inventory of the T. atroviride and T.virens genome, therefore, points to previously unknown mechanisms operating during biocontrol of plant pathogens. The availability of these genomes provides a unique opportunity to develop a deeper understanding of the processes fundamental to mycoparasitism and its application for the breeding of improved biocontrol strains for plant protection. To investigate the potential role in mycoparasitism, microarrays were used to examine T. virens transcript levels when confronted with a potential prey (the plant pathogen Rhizoctonia solani) before contact, during first physical contact and during overgrowth of the host. The study presented here is the result of this analysis.
Project description:The soilborne fungus, Verticillium dahliae, causes Verticillium wilt disease in plants. Verticillium wilt is difficult to control since V. dahliae is capable of persisting in the soil for 10 to15 years as melanized microsclerotia, rendering crop rotation strategies for disease control ineffective. Microsclerotia of V. dahliae overwinter and germinate to produce infectious hyphae that give rise to primary infections. Consequentially, microsclerotia formation, maintenance, and germination are critically important processes in the disease cycle of V. dahliae.
Project description:Cotton is the main source of natural fiber in the textile industry, making it one of the most economically important fiber crops in the world. Verticillium wilt, caused by the pathogenic fungus Verticillium dahlia, is one of the most damaging biotic factors limiting cotton production. Mechanistic details of cotton defense responses to verticillium wilt remain unclear. In this study, GFP-labeled strain of V. dahlia was used to track colonization in cotton roots, and clear conidial germination could be observed at 48 hours post-inoculation (hpi), marking this as a crucial time point during infection. Transcriptome analysis identified 1,523 and 8,270 differentially expressed genes (DEGs) at 24 hpi and 48 hpi, respectively. Metabolomic screening found 78 differentially accumulated metabolites (DAMs) at 48 hpi. Conjoint analysis indicated that the phenylpropanoid biosynthesis pathway was activated in cotton infected with V. dahliae. The five metabolites in the phenylpropanoid biosynthesis pathway, including caffeic acid, coniferyl alcohol, coniferin, scopoletin and scopolin, could significantly inhibit V. dahlia growth in vitro, implicating their roles in cotton resistance to Verticillium wilt. The findings expand our understanding of molecular mechanisms underlying the pathogen defense response against V. dahlia infection in upland cotton, which may lead to future insights into controlling Verticillium wilt disease.
Project description:Combating the action of plant pathogenic microorganisms by antagonistic or mycoparasitic fungi has been announced as an attractive biological alternative to the use of chemical fungicides since more than 20 years, and gains additional importance in current trends to environmentally friendly agriculture. Taxa of the fungal genus Hypocrea/Trichoderma (Ascomycota, Hypocreales, Hypocreaceae) contain prominent examples of such biocontrol agents, because they not only antagonize plant-pathogenic fungi, but are also often rhizosphere competent and can enhance plant growth. Identification of the primary factors that regulate the mycoparasitic behaviour and metabolic activities related to it will therefore allow the full ecological significance of this trait to be explored. We performed the analysis of the genome sequence from two mycoparasitic and rhizosphere competent Trichoderma spp. – T. atroviride and T. virens – and compare it to that of the saprophyte T. reesei. The predicted gene inventory of the T. atroviride and T.virens genome, therefore, points to previously unknown mechanisms operating during biocontrol of plant pathogens. The availability of these genomes provides a unique opportunity to develop a deeper understanding of the processes fundamental to mycoparasitism and its application for the breeding of improved biocontrol strains for plant protection. To investigate the potential role in mycoparasitism, microarrays were used to examine T. virens transcript levels when confronted with a potential prey (the plant pathogen Rhizoctonia solani) before contact, during first physical contact and during overgrowth of the host. The study presented here is the result of this analysis. Two biological pools by condition against a common reference control each sample hybridized in dye switch. On the two biological replicates we apply on the pretreated results the linear modeling approach implemented by lmFit and the empirical Bayes statistics implemented by eBayes from the limma R package (Smyth 2004). For mycoparasitism confrontation assays T. virens was grown on potato dextrose agar plates (BD Dicfo, Franklin Lakes, NJ, USA), covered with cellophane, in constant light at 25°C and harvested when the mycelia were ca. 5 mm apart (before contact), at contact of the mycelia and after T. virens had overgrown the host fungus Rhizoctonia solani by ca. 5 mm (after contact). As control T. virens was confronted with itself and harvested at contact. Peripheral hyphal zones from each confrontation stage were harvested and shock frozen in liquid nitrogen. Mycelia were ground to a fine powder under liquid nitrogen and total RNA was isolated using the guanidinium thiocyanate method (Sambrook, 2001).
Project description:Elevated atmospheric CO2 can influence the structure and function of rhizosphere microorganisms by altering root growth and the quality and quantity of compounds released into the rhizosphere via root exudation. In these studies we investigated the transcriptional responses of Bradyrhizobium japonicum cells growing in the rhizosphere of soybean plants exposed to elevated atmospheric CO2. The results of microarray analyses indicated that atmospheric elevated CO2 concentration indirectly influences on expression of large number of Bradyrhizobium genes through soybean roots. In addition, genes involved in C1 metabolism, denitrification and FixK2-associated genes, including those involved in nitrogen fixation, microanaerobic respiration, respiratory nitrite reductase, and heme biosynthesis, were significantly up-regulated under conditions of elevated CO2 in the rhizosphere, relative to plants and bacteria grown under ambient CO2 growth conditions. The expression profile of genes involved in lipochitinoligosaccharide Nod factor biosynthesis and negative transcriptional regulators of nodulation genes, nolA and nodD2, were also influenced by plant growth under conditions of elevated CO2. Taken together, results of these studies indicate that growth of soybeans under conditions of elevated atmospheric CO2 influences gene expressions in B. japonicum in the soybean rhizosphere, resulting in changes to carbon/nitrogen metabolism, respiration, and nodulation efficiency.
Project description:Verticillium dahliae is a soil-borne vascular pathogen that causes severe wilt symptoms in a wide range of plants. Co-culture of the fungus with Arabidopsis roots for 24 hours induces many changes in the gene expression profiles of both partners, even before defense-related phytohormone levels are induced in the plant. Both partners reprogram sugar and amino acid metabolism, activate genes for signal perception and transduction, and induce defense and stress responsive genes. Furthermore, analysis of Arabidopsis expression profiles suggests a redirection from growth to defense. The plant and fungal genes that rapidly respond to the presence of the partner might be crucial for early recognition steps and the future development of the interaction. Thus they are potential targets for the control of V. dahliae-induced wilt diseases.
Project description:Plants coexist in close proximity with numerous microorganisms in their rhizosphere. With certain microorganisms, plants establish mutualistic relationships that can confer physiological benefits to the interacting organisms, including enhanced nutrient assimilation or increased stress tolerance. The root-colonizing endophytic fungi Penicillium chrysogenum, Penicillium minioluteum, and Serendipita indica have been reported to enhance the drought stress tolerance of plants. However, to date, the molecular mechanisms triggered by these fungi in plants remain unexplored. This study presents a comparative analysis of the effects on mock- and fungus-infected tomato plants (var. Moneymaker) under drought stress conditions (40% field capacity) and control conditions (100% field capacity). The findings provide evidence for the induction of common response modules by the fungi.
Project description:To verify the pathogenicity of Lecanicillium psalliotae invasive pathogens on tsearch leaves, Lecanicillium psalliotae was identified by isolation and purification. sweet orange leaves were infested with it. The results of the experiments showed that 15 days after Lecanicillium psalliotae infested the leaves of sweet orange, yellow spots grew around the pores and irregular yellow spots appeared on both sides of the leaf veins. This was highly similar to the disease in the field, suggesting that Lecanicillium psalliotae is the causal agent of the yellow spots on sweet orange leaves that cause the leaves to wilt and fall off. In previous studies, Verticillium cutaneum was mainly identified as a biological control agent and a suspected pathogen. In this study, the pathogenicity of Verticillium cutaneum was verified for the first time as a causal agent of leaf spot disease of plants.
Project description:Communication between interacting organisms via bioactive molecules is widespread in nature and plays key roles in diverse biological processes. Small RNAs (sRNAs) can travel between host plants and filamentous pathogens to trigger trans-kingdom RNA interference (RNAi) in recipient cells and modulate plant defense and pathogen virulence. However, how trans-kingdom RNAi is regulated has rarely been reported. Here, we show that the secretory protein VdSSR1 (secretory silencing repressor 1) from Verticillium dahliae, a soil-borne phytopathogenic fungus that causes wilt diseases in a wide range of plant hosts, is required for fungal virulence in plants through the suppression of trans-kingdom RNAi.