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Title: Final Report: Exudation by Poplar Ectomycorrhizas: Qualitative and Quantitative Assessment of C Sequestration

Abstract

Study 1. We compared mycorrhizal Populus tremuloides inoculated with Laccaria bicolor and nonmycorrhizal (NM) P. tremuloides seedlings grown under different levels of P nutrition. Decreasing concentrations of P significantly increased the activity of reactive oxygen scavenging enzymes. In addition, phosphoenolpyruvate carboxylase activity increased under P limitation. P deficiency also increased organic acid exudation and total organic carbon exudation. Colonization by L. bicolor reduced the P concentration thresholds where these physiological changes occurred. Study 2. We assessed the influences of ectomycorrhizal colonization on phosphate limitation responses of trembling aspen. Photosynthetic CO2 uptake was reduced in NM poplar, but not in plants colonized by L. bicolor or P. involutus. Reductions in shoot and root biomass in NM plants were substantially greater than reductions in plants colonized by either ectomycorrhizal fungi. Leaf starch and sugar concentrations declined with Pi limitation across mycorrhizal treatments, but were higher in plants colonized by L. bicolor and P. involutus. In roots, starch concentrations were greater in NM plants with Pi limitation. In roots, sugars were significantly higher in NM plants compared to mycorrhizal plants and increased significantly in NM plants under Pi limitation. Concentrations were unaffected by Pi limitation in plants colonized by L. bicolor or P.more » involutus. Study 3. We analyzed proteins that were differentially expressed during the mycorrhizal association. A comparison of global protein expression elucidated broad differences in protein profiles between NM plants and plants colonized by ectomycorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi as well as differences between the ECM fungi L. bicolor and P. involutus. Plants colonized by P. involutus and G. intraradices exhibited unique patterns of up/down-regulated proteins compared to NM plants, whereas plants colonized by L. bicolor exhibited patterns of protein expression more aligned with NM plants. The greatest change in protein expression was in the areas of energy production and the TCA cycle. Among these proteins, fructose-bisphosphate and glyceraldehyde-3-phosphate dedydrogenase were notably up-regulated due to mycorrhizal colonization of aspen by L. bicolor. Pyruvate dehydrogenase, aldehyde dehydrogenase, and aconitate hydratase were up-regulated due to mycorrhizal colonized by P. involutus. Malate dehydrogenase, cinnamyl-alcohol dehydrogenase, and NADH-ubiquinone oxidoreductase proteins were up-regulated due to mycorrhizal colonization of aspen by G. intraradices. Study 4. Eight hybrid crosses of P. trichocarpa, P. deltoides and P. nigra were exposed to Al in solution culture. Resistance to Al varied by genotype and hybrid cross, with P. trichocarpa P. deltoides crosses being most resistant, P. trichocarpa P. nigra being intermediate and P. deltoides P. nigra being most sensitive to Al. Total root Al accumulation was not a good indicator of Al resistance/sensitivity. However, differences in sensitivity among genotypes were associated with Al uptake into the symplasm. Aluminum treatment increased callose and pectin concentrations of root tips more prominently in Al sensitive genotypes/hybrids. In Al sensitive genotypes, higher levels of symplastic Al accumulation correlated with elevated concentrations of citrate, malate, succinate or formate in root tips, whereas organic acid accumulation was not as pronounced in Al resistant genotypes. These findings suggest that exclusion of Al from the symplast is associated with Al resistance. Study 5. We assessed patterns of exudation in Al-resistant and Al-sensitive Populus hybrid crosses. Exposure to Al in solution induced the exudation of citrate and malate from the roots of both hybrid genotypes and altered the contributions of other organic acids to the exudation profiles. Citrate exudation was about 8-times greater in DTAC-7 (resistant) than OP-367 (sensitive). The analysis of total and cationic Al in solution indicated that the amount of bound Al in solution was three-times higher in solutions from DTAC-7 compared to OP-367 plants over both Al treatments. Study 6. We explored the growth, comparative physiology and transcriptional changes of poplar origin that were associated with ECM and/or AM colonization with low Pi availability. Microarray analysis revealed that the symbiosis-associated transcriptome of Populus involves a set of highly conserved genes that overlaps expressed ion other species. Pi-dependent changes in transcript levels involved the down-regulation of symbiosis-responsive genes encoding phosphate transporter proteins, pathogenesis-related proteins, and certain proteases. The up-regulation of genes encoding enzymes involved in carotenoid and apocarotenoid biosynthesis in AM colonized roots indicates that these pathways are specific to AM activation.« less

Authors:
Publication Date:
Research Org.:
West Virginia University, Morgantown, WV
Sponsoring Org.:
USDOE
OSTI Identifier:
1054600
Report Number(s):
DOE/ER64148-3
DOE Contract Number:  
FG02-06ER64148
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; Arbuscular mycorrhizae, ectomycorrhizae, gene expression, organic acid exudation, poplar, protein expression, stress responses

Citation Formats

Cumming, J R. Final Report: Exudation by Poplar Ectomycorrhizas: Qualitative and Quantitative Assessment of C Sequestration. United States: N. p., 2012. Web.
Cumming, J R. Final Report: Exudation by Poplar Ectomycorrhizas: Qualitative and Quantitative Assessment of C Sequestration. United States.
Cumming, J R. Mon . "Final Report: Exudation by Poplar Ectomycorrhizas: Qualitative and Quantitative Assessment of C Sequestration". United States.
@article{osti_1054600,
title = {Final Report: Exudation by Poplar Ectomycorrhizas: Qualitative and Quantitative Assessment of C Sequestration},
author = {Cumming, J R},
abstractNote = {Study 1. We compared mycorrhizal Populus tremuloides inoculated with Laccaria bicolor and nonmycorrhizal (NM) P. tremuloides seedlings grown under different levels of P nutrition. Decreasing concentrations of P significantly increased the activity of reactive oxygen scavenging enzymes. In addition, phosphoenolpyruvate carboxylase activity increased under P limitation. P deficiency also increased organic acid exudation and total organic carbon exudation. Colonization by L. bicolor reduced the P concentration thresholds where these physiological changes occurred. Study 2. We assessed the influences of ectomycorrhizal colonization on phosphate limitation responses of trembling aspen. Photosynthetic CO2 uptake was reduced in NM poplar, but not in plants colonized by L. bicolor or P. involutus. Reductions in shoot and root biomass in NM plants were substantially greater than reductions in plants colonized by either ectomycorrhizal fungi. Leaf starch and sugar concentrations declined with Pi limitation across mycorrhizal treatments, but were higher in plants colonized by L. bicolor and P. involutus. In roots, starch concentrations were greater in NM plants with Pi limitation. In roots, sugars were significantly higher in NM plants compared to mycorrhizal plants and increased significantly in NM plants under Pi limitation. Concentrations were unaffected by Pi limitation in plants colonized by L. bicolor or P. involutus. Study 3. We analyzed proteins that were differentially expressed during the mycorrhizal association. A comparison of global protein expression elucidated broad differences in protein profiles between NM plants and plants colonized by ectomycorrhizal (ECM) or arbuscular mycorrhizal (AM) fungi as well as differences between the ECM fungi L. bicolor and P. involutus. Plants colonized by P. involutus and G. intraradices exhibited unique patterns of up/down-regulated proteins compared to NM plants, whereas plants colonized by L. bicolor exhibited patterns of protein expression more aligned with NM plants. The greatest change in protein expression was in the areas of energy production and the TCA cycle. Among these proteins, fructose-bisphosphate and glyceraldehyde-3-phosphate dedydrogenase were notably up-regulated due to mycorrhizal colonization of aspen by L. bicolor. Pyruvate dehydrogenase, aldehyde dehydrogenase, and aconitate hydratase were up-regulated due to mycorrhizal colonized by P. involutus. Malate dehydrogenase, cinnamyl-alcohol dehydrogenase, and NADH-ubiquinone oxidoreductase proteins were up-regulated due to mycorrhizal colonization of aspen by G. intraradices. Study 4. Eight hybrid crosses of P. trichocarpa, P. deltoides and P. nigra were exposed to Al in solution culture. Resistance to Al varied by genotype and hybrid cross, with P. trichocarpa P. deltoides crosses being most resistant, P. trichocarpa P. nigra being intermediate and P. deltoides P. nigra being most sensitive to Al. Total root Al accumulation was not a good indicator of Al resistance/sensitivity. However, differences in sensitivity among genotypes were associated with Al uptake into the symplasm. Aluminum treatment increased callose and pectin concentrations of root tips more prominently in Al sensitive genotypes/hybrids. In Al sensitive genotypes, higher levels of symplastic Al accumulation correlated with elevated concentrations of citrate, malate, succinate or formate in root tips, whereas organic acid accumulation was not as pronounced in Al resistant genotypes. These findings suggest that exclusion of Al from the symplast is associated with Al resistance. Study 5. We assessed patterns of exudation in Al-resistant and Al-sensitive Populus hybrid crosses. Exposure to Al in solution induced the exudation of citrate and malate from the roots of both hybrid genotypes and altered the contributions of other organic acids to the exudation profiles. Citrate exudation was about 8-times greater in DTAC-7 (resistant) than OP-367 (sensitive). The analysis of total and cationic Al in solution indicated that the amount of bound Al in solution was three-times higher in solutions from DTAC-7 compared to OP-367 plants over both Al treatments. Study 6. We explored the growth, comparative physiology and transcriptional changes of poplar origin that were associated with ECM and/or AM colonization with low Pi availability. Microarray analysis revealed that the symbiosis-associated transcriptome of Populus involves a set of highly conserved genes that overlaps expressed ion other species. Pi-dependent changes in transcript levels involved the down-regulation of symbiosis-responsive genes encoding phosphate transporter proteins, pathogenesis-related proteins, and certain proteases. The up-regulation of genes encoding enzymes involved in carotenoid and apocarotenoid biosynthesis in AM colonized roots indicates that these pathways are specific to AM activation.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2012},
month = {11}
}

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