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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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Analysis of functional traits of endophytes cultured from Zea seed.Shown are (A–F) select examples of trait assays and (G) the complete summary grouped by Zea genotype. Shown are assays for (A) antagonism to E. coli; (B) growth in nitrogren free LGI media with only ACC as a nitrogen source; (C) growth promotion of tissue cultured potato one month after inoculation with (from L–R) Enterobacter cloacae, Cellulomonas denverensis, sterile buffer, or Burkholderia phytofirmans; (D) ability to solubilise tricalcium phosphate; (E) acetoin and butanediol production; and (F) extracellular digestion of cellulose. For panel (G), light yellow shading indicates that <25% of isolates from the Zea genotype indicated exhibited the trait, deep yellow indicates 25–50%, orange indicates 50–75%, and red indicates 75–100%.
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pone-0020396-g008: Analysis of functional traits of endophytes cultured from Zea seed.Shown are (A–F) select examples of trait assays and (G) the complete summary grouped by Zea genotype. Shown are assays for (A) antagonism to E. coli; (B) growth in nitrogren free LGI media with only ACC as a nitrogen source; (C) growth promotion of tissue cultured potato one month after inoculation with (from L–R) Enterobacter cloacae, Cellulomonas denverensis, sterile buffer, or Burkholderia phytofirmans; (D) ability to solubilise tricalcium phosphate; (E) acetoin and butanediol production; and (F) extracellular digestion of cellulose. For panel (G), light yellow shading indicates that <25% of isolates from the Zea genotype indicated exhibited the trait, deep yellow indicates 25–50%, orange indicates 50–75%, and red indicates 75–100%.

Mentions: The above endophytic traits were ranked based on how widespread they were amongst Zea genotypes. The most common endophytic traits were phosphate solubilization (found in 12/14 Zea genotypes), followed by acetoin production (12/14), cellulase and/or pectinase secretion (12/14) and growth on nitrogen-free media (11/14)(Figure 8G; Table S4). Moderately conserved endophytic traits found across Zea subgroups were ACC deaminase activity (8/14), antibiosis against bacteria (8/14) or yeast (8/14) and RNase secretion (8/14). Rare endophytic traits were auxin production (3/14) and siderophore secretion (3/14).


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

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

Analysis of functional traits of endophytes cultured from Zea seed.Shown are (A–F) select examples of trait assays and (G) the complete summary grouped by Zea genotype. Shown are assays for (A) antagonism to E. coli; (B) growth in nitrogren free LGI media with only ACC as a nitrogen source; (C) growth promotion of tissue cultured potato one month after inoculation with (from L–R) Enterobacter cloacae, Cellulomonas denverensis, sterile buffer, or Burkholderia phytofirmans; (D) ability to solubilise tricalcium phosphate; (E) acetoin and butanediol production; and (F) extracellular digestion of cellulose. For panel (G), light yellow shading indicates that <25% of isolates from the Zea genotype indicated exhibited the trait, deep yellow indicates 25–50%, orange indicates 50–75%, and red indicates 75–100%.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0020396-g008: Analysis of functional traits of endophytes cultured from Zea seed.Shown are (A–F) select examples of trait assays and (G) the complete summary grouped by Zea genotype. Shown are assays for (A) antagonism to E. coli; (B) growth in nitrogren free LGI media with only ACC as a nitrogen source; (C) growth promotion of tissue cultured potato one month after inoculation with (from L–R) Enterobacter cloacae, Cellulomonas denverensis, sterile buffer, or Burkholderia phytofirmans; (D) ability to solubilise tricalcium phosphate; (E) acetoin and butanediol production; and (F) extracellular digestion of cellulose. For panel (G), light yellow shading indicates that <25% of isolates from the Zea genotype indicated exhibited the trait, deep yellow indicates 25–50%, orange indicates 50–75%, and red indicates 75–100%.
Mentions: The above endophytic traits were ranked based on how widespread they were amongst Zea genotypes. The most common endophytic traits were phosphate solubilization (found in 12/14 Zea genotypes), followed by acetoin production (12/14), cellulase and/or pectinase secretion (12/14) and growth on nitrogen-free media (11/14)(Figure 8G; Table S4). Moderately conserved endophytic traits found across Zea subgroups were ACC deaminase activity (8/14), antibiosis against bacteria (8/14) or yeast (8/14) and RNase secretion (8/14). Rare endophytic traits were auxin production (3/14) and siderophore secretion (3/14).

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