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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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Persistence and migration of Zea seed endophytes in stems, roots and the rhizosphere.The 11 endophytes indicated were successfully tagged with GFP (pDSK-GFPuv, KanR) (out of 124 isolates attempted) and injected into maize stems. The 6 endophytes indicated migrated to roots and persisted for >5 days as shown by fluorescence microscopy and culturing from macerated root tissues onto R2A Kanamycin media. (A) Panteoa agglomerans shown spilling out of a metaxylem vessel. (B) Enterobacter asburiae spilling out of root vascular tissue. (C) Culturing confirmed that E. asburiae was present in the roots of two plants (top two quandrants) as well as in their rhizospheres (bottom two quadrants).
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pone-0020396-g010: Persistence and migration of Zea seed endophytes in stems, roots and the rhizosphere.The 11 endophytes indicated were successfully tagged with GFP (pDSK-GFPuv, KanR) (out of 124 isolates attempted) and injected into maize stems. The 6 endophytes indicated migrated to roots and persisted for >5 days as shown by fluorescence microscopy and culturing from macerated root tissues onto R2A Kanamycin media. (A) Panteoa agglomerans shown spilling out of a metaxylem vessel. (B) Enterobacter asburiae spilling out of root vascular tissue. (C) Culturing confirmed that E. asburiae was present in the roots of two plants (top two quandrants) as well as in their rhizospheres (bottom two quadrants).

Mentions: A number of seed endophytes had functions that suggested they might be important in the roots and rhizosphere including phosphate solubilization. To track seed endophytes in the maize plant body, 11 species of endophytes that had been successfully transformed with a broad host range constitutive GFP expressing vector pDSK-GFPuv [45] were injected into the stems of Pioneer 3751 plants (Figure 10). After 5 days of growth, plant roots were sampled for microbes using microscopy and culturing on selective agar media. Panteoa agglomerans isolated from B73 was observed in metaxylem vessels (Figure 10A) and Enterobacter asburiae isolated from Diploperennis in phloem cells at the base of plant stems (Figure 10B) demonstrating their ability to move systemically through vascular tissues. The plate recovery method also showed that these and several additional microbes could migrate to roots, including Citrobacter freundii from Nicaraguensis, Klebsiella pneumoniae 342 from Nicaraguensis, E. coli NBRI1707 from Chapalote, and Xanthomonas campestris from B73 (Figure 10C). These results also confirm that these microbes were endophytes.


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

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

Persistence and migration of Zea seed endophytes in stems, roots and the rhizosphere.The 11 endophytes indicated were successfully tagged with GFP (pDSK-GFPuv, KanR) (out of 124 isolates attempted) and injected into maize stems. The 6 endophytes indicated migrated to roots and persisted for >5 days as shown by fluorescence microscopy and culturing from macerated root tissues onto R2A Kanamycin media. (A) Panteoa agglomerans shown spilling out of a metaxylem vessel. (B) Enterobacter asburiae spilling out of root vascular tissue. (C) Culturing confirmed that E. asburiae was present in the roots of two plants (top two quandrants) as well as in their rhizospheres (bottom two quadrants).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020396-g010: Persistence and migration of Zea seed endophytes in stems, roots and the rhizosphere.The 11 endophytes indicated were successfully tagged with GFP (pDSK-GFPuv, KanR) (out of 124 isolates attempted) and injected into maize stems. The 6 endophytes indicated migrated to roots and persisted for >5 days as shown by fluorescence microscopy and culturing from macerated root tissues onto R2A Kanamycin media. (A) Panteoa agglomerans shown spilling out of a metaxylem vessel. (B) Enterobacter asburiae spilling out of root vascular tissue. (C) Culturing confirmed that E. asburiae was present in the roots of two plants (top two quandrants) as well as in their rhizospheres (bottom two quadrants).
Mentions: A number of seed endophytes had functions that suggested they might be important in the roots and rhizosphere including phosphate solubilization. To track seed endophytes in the maize plant body, 11 species of endophytes that had been successfully transformed with a broad host range constitutive GFP expressing vector pDSK-GFPuv [45] were injected into the stems of Pioneer 3751 plants (Figure 10). After 5 days of growth, plant roots were sampled for microbes using microscopy and culturing on selective agar media. Panteoa agglomerans isolated from B73 was observed in metaxylem vessels (Figure 10A) and Enterobacter asburiae isolated from Diploperennis in phloem cells at the base of plant stems (Figure 10B) demonstrating their ability to move systemically through vascular tissues. The plate recovery method also showed that these and several additional microbes could migrate to roots, including Citrobacter freundii from Nicaraguensis, Klebsiella pneumoniae 342 from Nicaraguensis, E. coli NBRI1707 from Chapalote, and Xanthomonas campestris from B73 (Figure 10C). These results also confirm that these microbes were endophytes.

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