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Date of Award

2016

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Biochemistry and Molecular Biology (PhD)

Administrative Home Department

Department of Biological Sciences

Advisor 1

Ramakrishna Wusirika

Advisor 2

Rupali Datta

Committee Member 1

Chandrashekhar Joshi

Committee Member 2

Erik Lilleskov

Abstract

In the current study, two C4 plants, sorghum (BTx623) and maize (rugosa) grown in mining-impacted soil were subjected to plant growth promoting bacteria (PGPB) Pseudomonas sp. TLC 6-6.5-4 and arbuscular mycorrhiza individually and combined. Seedlings were maintained in the greenhouse under the same conditions for the same period of time for all three treatments. Three treatments were used, Pseudomonas sp. TLC 6-6.5-4 (B group), arbuscular mycorrhizal mix (My group), and combination of PGPB and mycorrhiza (My+B group). Dead inoculum was used as the control group. To gain insights on how plants react at the molecular level, data was collected at the end of maize life cycle after 62 days and sorghum after 90 days. Plant physiological responses under different treatments were investigated. These included maize and sorghum biomass, element uptake and changes in metabolites. Biochemical and molecular mechanisms involved in sorghum and maize tolerance were identified. Further, proteomic analysis was integrated with physiological responses. Our results revealed that different microbial treatments lead to different physiological responses in maize and sorghum. The biomass and element uptake increased in all of the three treatments (B, My and My+B) for both sorghum and maize with minor variations. In addition, three metabolic pathways were common between maize and sorghum based on upregulated metabolites. We hypothesize that plants ensure carbon flux and energy supply for carbohydrate integration into biomass through fatty acid synthesis and glyoxylate metabolism whereas, alanine, aspartate and glutamate metabolism are used to facilitate nitrogen incorporation. The increase of element uptake associated with metabolite changes in maize or sorghum root might be due to metabolic reprogramming to overcome macronutrient deficiency. Sorghum protein analysis showed common upregulation of 45 proteins. Among these proteins, fructokinase correlated positively with biomass, primary element uptake and metabolites associated with biomass and element uptake. The PGPB showed the highest number of upregulated proteins, where one-fourth of them involved oxidoreductase and DNA repair activity. These findings confirm that PGPB increased sorghum tolerance through ROS scavenging system to balance cellular function during stress.

In the current study, two C4 plants, sorghum (BTx623) and maize (rugosa) grown in mining-impacted soil were subjected to plant growth promoting bacteria (PGPB) Pseudomonas sp. TLC 6-6.5-4 and arbuscular mycorrhiza individually and combined. Seedlings were maintained in the greenhouse under the same conditions for the same period of time for all three treatments. Three treatments were used, Pseudomonas sp. TLC 6-6.5-4 (B group), arbuscular mycorrhizal mix (My group), and combination of PGPB and mycorrhiza (My+B group). Dead inoculum was used as the control group. To gain insights on how plants react at the molecular level, data was collected at the end of maize life cycle after 62 days and sorghum after 90 days. Plant physiological responses under different treatments were investigated. These included maize and sorghum biomass, element uptake and changes in metabolites. Biochemical and molecular mechanisms involved in sorghum and maize tolerance were identified. Further, proteomic analysis was integrated with physiological responses. Our results revealed that different microbial treatments lead to different physiological responses in maize and sorghum. The biomass and element uptake increased in all of the three treatments (B, My and My+B) for both sorghum and maize with minor variations. In addition, three metabolic pathways were common between maize and sorghum based on upregulated metabolites. We hypothesize that plants ensure carbon flux and energy supply for carbohydrate integration into biomass through fatty acid synthesis and glyoxylate metabolism whereas, alanine, aspartate and glutamate metabolism are used to facilitate nitrogen incorporation. The increase of element uptake associated with metabolite changes in maize or sorghum root might be due to metabolic reprogramming to overcome macronutrient deficiency. Sorghum protein analysis showed common upregulation of 45 proteins. Among these proteins, fructokinase correlated positively with biomass, primary element uptake and metabolites associated with biomass and element uptake. The PGPB showed the highest number of upregulated proteins, where one-fourth of them involved oxidoreductase and DNA repair activity. These findings confirm that PGPB increased sorghum tolerance through ROS scavenging system to balance cellular function during stress.

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