Pervasive effects of an endophytic fungus on host genetic and phenotypic expression in a tropical tree (part 1)
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ABSTRACT: Inoculation of endophyte-free (E-) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant foliar fungal endophyte in healthy T. cacao, induced significant changes in the expression of hundreds of host genes. Further, E+ leaves exhibit enhanced pathogen resistance, increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes that all correspond to the changes in expression of specific functional genes in related pathways. Moreover, a cacao gene highly up-regulated in E+ leaves increases pathogen resistance apart from any direct endophyte effects. Thus, benefits of increased pathogen resistance in E+ plants are partially due to enhanced induction of intrinsic host defense pathways, and potential costs include reduced photosynthetic capacity and endophyte metabolism of host tissues. Similar effects are likely to be properties of most plant-endophyte interactions, suggesting general relevance to the design and interpretation of studies of genetic and phenotypic expression in plants.
Project description:Inoculation of endophyte-free (E-) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant foliar fungal endophyte in healthy T. cacao, induced significant changes in the expression of hundreds of host genes. Further, E+ leaves exhibit enhanced pathogen resistance, increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes that all correspond to the changes in expression of specific functional genes in related pathways. Moreover, a cacao gene highly up-regulated in E+ leaves increases pathogen resistance apart from any direct endophyte effects. Thus, benefits of increased pathogen resistance in E+ plants are partially due to enhanced induction of intrinsic host defense pathways, and potential costs include reduced photosynthetic capacity and endophyte metabolism of host tissues. Similar effects are likely to be properties of most plant-endophyte interactions, suggesting general relevance to the design and interpretation of studies of genetic and phenotypic expression in plants.
Project description:Inoculation of endophyte-free (E-) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant foliar fungal endophyte in healthy T. cacao, induced significant changes in the expression of hundreds of host genes. Further, E+ leaves exhibit enhanced pathogen resistance, increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes that all correspond to the changes in expression of specific functional genes in related pathways. Moreover, a cacao gene highly up-regulated in E+ leaves increases pathogen resistance apart from any direct endophyte effects. Thus, benefits of increased pathogen resistance in E+ plants are partially due to enhanced induction of intrinsic host defense pathways, and potential costs include reduced photosynthetic capacity and endophyte metabolism of host tissues. Similar effects are likely to be properties of most plant-endophyte interactions, suggesting general relevance to the design and interpretation of studies of genetic and phenotypic expression in plants.
Project description:Inoculation of endophyte-free (E-) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant foliar fungal endophyte in healthy T. cacao, induced significant changes in the expression of hundreds of host genes. Further, E+ leaves exhibit enhanced pathogen resistance, increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes that all correspond to the changes in expression of specific functional genes in related pathways. Moreover, a cacao gene highly up-regulated in E+ leaves increases pathogen resistance apart from any direct endophyte effects. Thus, benefits of increased pathogen resistance in E+ plants are partially due to enhanced induction of intrinsic host defense pathways, and potential costs include reduced photosynthetic capacity and endophyte metabolism of host tissues. Similar effects are likely to be properties of most plant-endophyte interactions, suggesting general relevance to the design and interpretation of studies of genetic and phenotypic expression in plants. This was a time course experiment, which objective was to assess gene expression changes in leaves of Theobroma cacao due to inoculation with endophyte Colletotrichum tropicale, over a period of two weeks. Three un-inoculated T. cacao leaves (E-) were collected at time 0, just prior to inoculation, and four T. cacao leaves inoculated with C. tropicale (E+) were collected at 3, 7, and 14 dpi, each leaf from a different plant. Sampled leaves were of developmental stage C-D (MejM-CM--a et al. 2012). MejM-CM--a, L.C., Guiltinan, M., J. , Shi, Z., Landherr, L., and Maximova, S., N. (2012). Expression of Designed Antimicrobial Peptides in Theobroma cacao L. Trees Reduces Leaf Necrosis Caused by Phytophthora spp, in Small Wonders: Peptides for Disease Control. American Chemical Society), 379-395.
Project description:Inoculation of endophyte-free (E-) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant foliar fungal endophyte in healthy T. cacao, induced significant changes in the expression of hundreds of host genes. Further, E+ leaves exhibit enhanced pathogen resistance, increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes that all correspond to the changes in expression of specific functional genes in related pathways. Moreover, a cacao gene highly up-regulated in E+ leaves increases pathogen resistance apart from any direct endophyte effects. Thus, benefits of increased pathogen resistance in E+ plants are partially due to enhanced induction of intrinsic host defense pathways, and potential costs include reduced photosynthetic capacity and endophyte metabolism of host tissues. Similar effects are likely to be properties of most plant-endophyte interactions, suggesting general relevance to the design and interpretation of studies of genetic and phenotypic expression in plants. The objective of this experiment was to identify Theobroma cacao genes that are differentially expressed between leaves inoculated with fungal endophyte Colletotrichum tropicale (E+ leaves) and control un-inoculated leaves (E- leaves) 3 days post endophyte inoculation. The experiment was conducted in a Percival growth chamber (model I35LL, 115 volts, 1/4 Hp, series: 8503122.16, Percival Scientific, Inc., Perry IA) with 12/12 h light/dark photoperiod and temperatures of 30M-BM-:C and 26M-BM-:C respectively. Inoculation was done by aspersion of endophyte spores (2X10^6 spore/ml) to a group of T. cacao seedlings and a second group of seedlings were maintained as control un-inoculated (E- leaves). Then three biological replicates (each one consisting of one leaf from different plants) per treatment E+ and four leaves per treatment E- leaves) were collected and processed for a two color oligo microarray analysis.
Project description:Inoculation of endophyte-free (E-) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant foliar fungal endophyte in healthy T. cacao, induced significant changes in the expression of hundreds of host genes. Further, E+ leaves exhibit enhanced pathogen resistance, increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes that all correspond to the changes in expression of specific functional genes in related pathways. Moreover, a cacao gene highly up-regulated in E+ leaves increases pathogen resistance apart from any direct endophyte effects. Thus, benefits of increased pathogen resistance in E+ plants are partially due to enhanced induction of intrinsic host defense pathways, and potential costs include reduced photosynthetic capacity and endophyte metabolism of host tissues. Similar effects are likely to be properties of most plant-endophyte interactions, suggesting general relevance to the design and interpretation of studies of genetic and phenotypic expression in plants. The objective of this experiment was to identify Theobroma cacao genes that are differentially expressed between leaves inoculated with fungal endophyte Colletotrichum tropicale (E+ leaves) and control un-inoculated leaves (E- leaves) 14 days post last endophyte inoculation. The experiment was conducted in a Percival growth chambers (model I35LL, 115 volts, 1/4 Hp, series: 8503122.16, Percival Scientific, Inc., Perry IA) with 12/12 h light/dark photoperiod and temperatures of 30M-BM-:C and 26M-BM-:C respectively. A total of four endophyte spore inoculations (1X10^6 spore/ml) were made by aspersion to a group of T. cacao seedlings and a second group of seedlings were maintained as un-inoculated. Then six biological replicates per treatment (E+ leaves and six E- leaves) each one belonging from a different seedling were collected and processed for a two color oligo microarray analysis. A total of six arrays were processed, each one hybridized to an inoculated and a control un-inoculated sample in a dye swap design.
Project description:Cacao (Theobroma cacao) is a highly valuable crop with growing demands in the global market. However, cacao farmers often face challenges posed by black pod disease caused by Phytophthora spp. with P. palmivora as the most dominant. Regulations of various gene expression influence plant resistance to pathogens. One mechanism involves targeting mRNA of virulence genes in the invading pathogens, suppressing their infection. However, resistance also could be suppressed by plant-derived miRNAs that target their own defense genes. The objective of this study is to identify differentially expressed miRNAs in black pod resistant and susceptible Cacao varieties and to predict their targets in T. cacao and P. palmivora transcripts. In our research, 54 known miRNAs from 40 miRNA families and 67 Novel miRNAs were identified. As much as 17 miRNAs were differentially expressed in susceptible variety compared to resistant one, with 9 miRNAs were upregulated and 8 miRNAs downregulated. In T. cacao transcripts, the upregulated miRNAs were predicted to target several genes, including defense genes. The suppression of these defense genes can lead to a reduction in plant resistance against pathogen infection. While in P. palmivora transcripts, the upregulated miRNAs were predicted to target several genes, including P. palmivora effector genes and other important metabolism activities genes. In the future, limiting expression of miRNAs that target T. cacao's defense genes and applying miRNAs that target P. palmivora effector genes hold promise for enhancing cacao plant resistance against P. palmivora infection.
Project description:The hydroxycinnamic acid amides (HCAAs) are a diverse group of plant specialized phenylpropanoid metabolites distributed widely in the plant kingdom and are known to be involved in tolerance to abiotic and biotic stress. The HCAA clovamide is reported in a small number of distantly related species. To explore the contribution of specialized metabolites to disease resistance in cacao (Theobroma cacao L., chocolate tree), we performed untargeted metabolomics using liquid chromatography – tandem mass spectrometry (LC-MS/MS) and compared the basal metabolite profiles in leaves of two cacao genotypes with contrasting levels of susceptibility to Phytophthora spp. Leaves of the tolerant genotype ‘Scavina 6’ were found to accumulate dramatically higher levels of clovamide and several other HCAAs compared to the susceptible ‘Imperial College Selection 1’ (‘ICS1’). Clovamide was the most abundant metabolite in ‘Scavina 6’ leaf extracts based on MS signal, and was up to 58-fold higher in ‘Scavina 6’ than in ‘ICS1’. In vitro assays demonstrated that clovamide inhibits growth of three pathogens of cacao in the genus Phytophthora, is a substrate for cacao polyphenol oxidase, and is a contributor to enzymatic browning. Furthermore, clovamide inhibited proteinase and pectinase in vitro, activities associated with defense in plant-pathogen interactions. Fruit epidermal peels from both genotypes contained substantial amounts of clovamide, but two sulfated HCAAs were present at high abundance exclusively in ‘Scavina 6’ suggesting a potential functional role of these compounds. The potential to breed cacao with increased HCAAs for improved agricultural performance is discussed.