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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.

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A phylogenetic tree of bacterial 16S rDNA sequences from Zea seed endophyte clones and cultured isolates.A multisequence alignment of the 16S region bounded by basepairs 867–1458 on an E. coli K12 reference sequence was used to generate a UPGMA tree. Included are sequences from clones (UnculturedbacteriumDJMX) and cultured isolates (Genus<StrainDJM-Plate#>) which are identified in Tables S2 and S3. Bacterial classes are labelled in red letters at major branch points.
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pone-0020396-g011: A phylogenetic tree of bacterial 16S rDNA sequences from Zea seed endophyte clones and cultured isolates.A multisequence alignment of the 16S region bounded by basepairs 867–1458 on an E. coli K12 reference sequence was used to generate a UPGMA tree. Included are sequences from clones (UnculturedbacteriumDJMX) and cultured isolates (Genus<StrainDJM-Plate#>) which are identified in Tables S2 and S3. Bacterial classes are labelled in red letters at major branch points.

Mentions: Finally, in order to gain an understanding of the phylogenetic relationships between endophytes isolated from Zea seeds, 16S rDNA sequences from all clones and cultured isolates were aligned and trimmed to a region pertaining to base pairs 867–1458 on an E. coli K12 reference 16S sequence, and this alignment was then used to construct a UPGMA tree (Figure 11). This phylogenetic analysis shows γ-proteobacteria were the most abundant class of microbes observed in this study, with Enterobacter and Panteoa as the most common genera. Also represented were the classes α-proteobacteria, β-proteobacteria, Bacilli, Actinobacteria, Clostridia, Deinococci and an unknown class. Clostridia and the unknown class were only represented in the clone library. Conversely, the classes Actinobacteria and Deinococci were only represented by cultured isolates, with no cloned sequences observed.


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

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

A phylogenetic tree of bacterial 16S rDNA sequences from Zea seed endophyte clones and cultured isolates.A multisequence alignment of the 16S region bounded by basepairs 867–1458 on an E. coli K12 reference sequence was used to generate a UPGMA tree. Included are sequences from clones (UnculturedbacteriumDJMX) and cultured isolates (Genus<StrainDJM-Plate#>) which are identified in Tables S2 and S3. Bacterial classes are labelled in red letters at major branch points.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020396-g011: A phylogenetic tree of bacterial 16S rDNA sequences from Zea seed endophyte clones and cultured isolates.A multisequence alignment of the 16S region bounded by basepairs 867–1458 on an E. coli K12 reference sequence was used to generate a UPGMA tree. Included are sequences from clones (UnculturedbacteriumDJMX) and cultured isolates (Genus<StrainDJM-Plate#>) which are identified in Tables S2 and S3. Bacterial classes are labelled in red letters at major branch points.
Mentions: Finally, in order to gain an understanding of the phylogenetic relationships between endophytes isolated from Zea seeds, 16S rDNA sequences from all clones and cultured isolates were aligned and trimmed to a region pertaining to base pairs 867–1458 on an E. coli K12 reference 16S sequence, and this alignment was then used to construct a UPGMA tree (Figure 11). This phylogenetic analysis shows γ-proteobacteria were the most abundant class of microbes observed in this study, with Enterobacter and Panteoa as the most common genera. Also represented were the classes α-proteobacteria, β-proteobacteria, Bacilli, Actinobacteria, Clostridia, Deinococci and an unknown class. Clostridia and the unknown class were only represented in the clone library. Conversely, the classes Actinobacteria and Deinococci were only represented by cultured isolates, with no cloned sequences observed.

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