Date of Award

12-2019

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology/Molecular, Cellular, and Organismal Biology

First Advisor

Adán Colón-Carmona

Second Advisor

Katherine E. Gibson

Third Advisor

Richard V. Kesseli

Abstract

The present study identified genes from Arabidopsis thaliana involved in the recruitment of microbes to the plant’s rhizosphere and their modulation. Among the genes were ATP binding cassette (ABC) transporters and genes involved in the synthesis of indole glucosinolates. Loss of function “knockouts” lines and one overexpressor line were used to better comprehend the involvement that these genes have in the assembly of the bacterial community residing in the rhizosphere of A. thaliana. Next generation sequencing technology was used to profile the rhizobacterial community from the different plant lines and the generation of a root exudate profiles were used to conclude that these group of genes not only impact the presence and absence of microorganism such as plant growth promoting rhizobacteria, but also their abundance in the plant’s rhizosphere. Loss of function “knockouts” from different ABC transporters were used to identify their involvement in shifting their rhizobacterial community when compared to the wild type community of A. thaliana. Or results suggest that the ABC transporter PDR9 plays a role in the assembly of the A. thaliana rhizosphere microbiome. The abiotic stressor phenanthrene was used to investigate whether ABC transporters play a role in the plant’s response towards this contaminant by aiding in its compartmentalization as well as in the recruitment of beneficial microbes capable of breaking down this polycyclic aromatic hydrocarbon. Our results suggest that the ABC transporter PDR9 plays a role in the transportation of this compound. Moreover, the ABC transporters PDR4, PDR7 and PDR9 can potentially recruit beneficial microbes in the presence of phenanthrene.

In order to study the role that tryptophan-derived indole glucosinolates (IGs) have on the assembly of the A. thaliana rhizobacterial community, an overexpressor line and a double mutant line were used to assess if the disruption of endogenous levels of IGs impact the rhizobacterial community. Our results show that increasing endogenous levels of IG result in higher bacterial richness when compared to the wild type, whereas, decreasing the IGs levels changes the plant’s root exudate profile when compared to the wild type.

Comments

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