Limits...
Conservation and diversity of seed associated endophytes in Zea across boundaries of evolution, ethnography and ecology.

Johnston-Monje D, Raizada MN - PLoS ONE (2011)

Bottom Line: Of these traits, phosphate solubilization and production of acetoin/butanediol were the most commonly observed.An isolate from the giant Mexican landrace Mixteco, with 100% identity to Burkholderia phytofirmans, significantly promoted shoot potato biomass.Conservation and diversity in Zea-microbe relationships are discussed in the context of ecology, crop domestication, selection and migration.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada.

ABSTRACT
Endophytes are non-pathogenic microbes living inside plants. We asked whether endophytic species were conserved in the agriculturally important plant genus Zea as it became domesticated from its wild ancestors (teosinte) to modern maize (corn) and moved from Mexico to Canada. Kernels from populations of four different teosintes and 10 different maize varieties were screened for endophytic bacteria by culturing, cloning and DNA fingerprinting using terminal restriction fragment length polymorphism (TRFLP) of 16S rDNA. Principle component analysis of TRFLP data showed that seed endophyte community composition varied in relation to plant host phylogeny. However, there was a core microbiota of endophytes that was conserved in Zea seeds across boundaries of evolution, ethnography and ecology. The majority of seed endophytes in the wild ancestor persist today in domesticated maize, though ancient selection against the hard fruitcase surrounding seeds may have altered the abundance of endophytes. Four TRFLP signals including two predicted to represent Clostridium and Paenibacillus species were conserved across all Zea genotypes, while culturing showed that Enterobacter, Methylobacteria, Pantoea and Pseudomonas species were widespread, with γ-proteobacteria being the prevalent class. Twenty-six different genera were cultured, and these were evaluated for their ability to stimulate plant growth, grow on nitrogen-free media, solubilize phosphate, sequester iron, secrete RNAse, antagonize pathogens, catabolize the precursor of ethylene, produce auxin and acetoin/butanediol. Of these traits, phosphate solubilization and production of acetoin/butanediol were the most commonly observed. An isolate from the giant Mexican landrace Mixteco, with 100% identity to Burkholderia phytofirmans, significantly promoted shoot potato biomass. GFP tagging and maize stem injection confirmed that several seed endophytes could spread systemically through the plant. One seed isolate, Enterobacter asburiae, was able to exit the root and colonize the rhizosphere. Conservation and diversity in Zea-microbe relationships are discussed in the context of ecology, crop domestication, selection and migration.

Show MeSH

Related in: MedlinePlus

Biplot diagrams to show the relatedness of endophytic microbial communities between Zea genotypes.The analysis is based on principle component analysis (PCA) of bacterial 16S rDNA terminal fragment length polymorphism (TRFLP) fingerprints. Shown are PCA analysis for (A) first generation seeds, (B) second generation seeds, and (C) stems. Vectors are drawn in red and represent the different Zea genotype samples. Diagrams are biplots of the first and second principle components, and are based on covariance between samples for differently sized forward and reverse terminal fragments (not shown). Angles between vectors represent the degree of covariance between samples, and are summarized on the vertical bars next to each biplot. The genotypes Nal-Tel, Tuxpeno, Jala, Pioneer 3751, and B73, lack phylogenetic support in this study, so they are omitted from vector angle bars on the right.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3108599&req=5

pone-0020396-g002: Biplot diagrams to show the relatedness of endophytic microbial communities between Zea genotypes.The analysis is based on principle component analysis (PCA) of bacterial 16S rDNA terminal fragment length polymorphism (TRFLP) fingerprints. Shown are PCA analysis for (A) first generation seeds, (B) second generation seeds, and (C) stems. Vectors are drawn in red and represent the different Zea genotype samples. Diagrams are biplots of the first and second principle components, and are based on covariance between samples for differently sized forward and reverse terminal fragments (not shown). Angles between vectors represent the degree of covariance between samples, and are summarized on the vertical bars next to each biplot. The genotypes Nal-Tel, Tuxpeno, Jala, Pioneer 3751, and B73, lack phylogenetic support in this study, so they are omitted from vector angle bars on the right.

Mentions: PCA analysis of covariance was performed on seed and stem 16S rDNA TRFLP results (Table S1) to statistically evaluate if endophyte community composition reflects evolutionary and/or ecological relationships of their host plants (Figure 2). Endophytes from first generation seed obtained from plants growing in different geographic environments show a striking pattern of covariation that recapitulates the phylogenetic pattern of their Zea hosts (Figure 1, 2A). Endophytes from distinct Zea species (Diploperennis and Nicaraguensis) were placed at one end of the spectrum, followed by the direct ancestors of modern maize (Parviglumis and Mexicana), then ancestral subspecies (Bolita and Mixteco), terminating in more derived (Chapalote and Cristalino) and temperate landraces (Gaspe). Mature second generation seed obtained from plants growing in the same temperate field were obtained from only a subset of genotypes, and their endophytes showed a similar pattern of covariation to first generation seed except that Chapalote appeared as an outlier (Figure 2B). Unlike seeds, endophytes in second generation stems appeared random with respect to Zea evolution (Figure 2C).


Conservation and diversity of seed associated endophytes in Zea across boundaries of evolution, ethnography and ecology.

Johnston-Monje D, Raizada MN - PLoS ONE (2011)

Biplot diagrams to show the relatedness of endophytic microbial communities between Zea genotypes.The analysis is based on principle component analysis (PCA) of bacterial 16S rDNA terminal fragment length polymorphism (TRFLP) fingerprints. Shown are PCA analysis for (A) first generation seeds, (B) second generation seeds, and (C) stems. Vectors are drawn in red and represent the different Zea genotype samples. Diagrams are biplots of the first and second principle components, and are based on covariance between samples for differently sized forward and reverse terminal fragments (not shown). Angles between vectors represent the degree of covariance between samples, and are summarized on the vertical bars next to each biplot. The genotypes Nal-Tel, Tuxpeno, Jala, Pioneer 3751, and B73, lack phylogenetic support in this study, so they are omitted from vector angle bars on the right.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3108599&req=5

pone-0020396-g002: Biplot diagrams to show the relatedness of endophytic microbial communities between Zea genotypes.The analysis is based on principle component analysis (PCA) of bacterial 16S rDNA terminal fragment length polymorphism (TRFLP) fingerprints. Shown are PCA analysis for (A) first generation seeds, (B) second generation seeds, and (C) stems. Vectors are drawn in red and represent the different Zea genotype samples. Diagrams are biplots of the first and second principle components, and are based on covariance between samples for differently sized forward and reverse terminal fragments (not shown). Angles between vectors represent the degree of covariance between samples, and are summarized on the vertical bars next to each biplot. The genotypes Nal-Tel, Tuxpeno, Jala, Pioneer 3751, and B73, lack phylogenetic support in this study, so they are omitted from vector angle bars on the right.
Mentions: PCA analysis of covariance was performed on seed and stem 16S rDNA TRFLP results (Table S1) to statistically evaluate if endophyte community composition reflects evolutionary and/or ecological relationships of their host plants (Figure 2). Endophytes from first generation seed obtained from plants growing in different geographic environments show a striking pattern of covariation that recapitulates the phylogenetic pattern of their Zea hosts (Figure 1, 2A). Endophytes from distinct Zea species (Diploperennis and Nicaraguensis) were placed at one end of the spectrum, followed by the direct ancestors of modern maize (Parviglumis and Mexicana), then ancestral subspecies (Bolita and Mixteco), terminating in more derived (Chapalote and Cristalino) and temperate landraces (Gaspe). Mature second generation seed obtained from plants growing in the same temperate field were obtained from only a subset of genotypes, and their endophytes showed a similar pattern of covariation to first generation seed except that Chapalote appeared as an outlier (Figure 2B). Unlike seeds, endophytes in second generation stems appeared random with respect to Zea evolution (Figure 2C).

Bottom Line: Of these traits, phosphate solubilization and production of acetoin/butanediol were the most commonly observed.An isolate from the giant Mexican landrace Mixteco, with 100% identity to Burkholderia phytofirmans, significantly promoted shoot potato biomass.Conservation and diversity in Zea-microbe relationships are discussed in the context of ecology, crop domestication, selection and migration.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Agriculture, University of Guelph, Guelph, Ontario, Canada.

ABSTRACT
Endophytes are non-pathogenic microbes living inside plants. We asked whether endophytic species were conserved in the agriculturally important plant genus Zea as it became domesticated from its wild ancestors (teosinte) to modern maize (corn) and moved from Mexico to Canada. Kernels from populations of four different teosintes and 10 different maize varieties were screened for endophytic bacteria by culturing, cloning and DNA fingerprinting using terminal restriction fragment length polymorphism (TRFLP) of 16S rDNA. Principle component analysis of TRFLP data showed that seed endophyte community composition varied in relation to plant host phylogeny. However, there was a core microbiota of endophytes that was conserved in Zea seeds across boundaries of evolution, ethnography and ecology. The majority of seed endophytes in the wild ancestor persist today in domesticated maize, though ancient selection against the hard fruitcase surrounding seeds may have altered the abundance of endophytes. Four TRFLP signals including two predicted to represent Clostridium and Paenibacillus species were conserved across all Zea genotypes, while culturing showed that Enterobacter, Methylobacteria, Pantoea and Pseudomonas species were widespread, with γ-proteobacteria being the prevalent class. Twenty-six different genera were cultured, and these were evaluated for their ability to stimulate plant growth, grow on nitrogen-free media, solubilize phosphate, sequester iron, secrete RNAse, antagonize pathogens, catabolize the precursor of ethylene, produce auxin and acetoin/butanediol. Of these traits, phosphate solubilization and production of acetoin/butanediol were the most commonly observed. An isolate from the giant Mexican landrace Mixteco, with 100% identity to Burkholderia phytofirmans, significantly promoted shoot potato biomass. GFP tagging and maize stem injection confirmed that several seed endophytes could spread systemically through the plant. One seed isolate, Enterobacter asburiae, was able to exit the root and colonize the rhizosphere. Conservation and diversity in Zea-microbe relationships are discussed in the context of ecology, crop domestication, selection and migration.

Show MeSH
Related in: MedlinePlus