Date of Award

8-2024

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Richard V. Kesseli

Second Advisor

Adán Colón-Carmona

Third Advisor

Michael P. Shiaris, Douglas Woodhams

Abstract

Developmental stage, root system architecture and rhizodeposition are among the known ways that plants modulate their physical interactions with bacteria in the rhizosphere, the zone of soil under the direct influence of plant roots. The genes involved in these interactions are largely unknown. In this study, a population of Arabidopsis recombinant inbred lines (RILs) derived from a cross between Cvi (Cape Verde Island) and Ler (Germany) identified quantitative trait loci (QTLs) influencing bacteria inhabiting the rhizosphere. Using a simple community fingerprinting technique, terminal-restriction fragment length polymorphisms (T-RFLPs), a core fingerprint of bacterial 16s rDNA was targeted for quantitative genetic analysis. While Cvi and Ler showed no major differences, increases in genetic variance (broad-sense heritability) among the RILs could be attributed to multiple QTL, some with opposing effects. Genetic correlations were predominantly weak, suggesting multiple distinct genetic architectures influence rhizosphere bacteria. Across 45 terminal-restriction fragments (T-RFs) considered in QTL mapping, 18 QTL influencing 14 T-RFs were detected. Conditional QTL mapping revealed four of these QTL could be categorized as dependent on changes in plant development. The two most significant QTL detected were independent of plant development and explained 14-19% of phenotypic variance and 31-52% of broad-sense heritability. A large clone library comprised of 709 sequences revealed the dominant phyla (>2% of the library) as Proteobacteria (59.5%), Bacteroidetes (23.9%), Verrucomicrobia (4.1%), Firmicutes (3.1%), Armatimonadetes (2.5%) and Actinobacteria (2%). Matching T-RFs to the library suggested QTL operate mostly at lower taxonomic ranks. These results provide valuable insights into the plant genetic architecture influencing rhizosphere bacteria and provide a resource for mining Arabidopsis candidate genes in future studies.

Comments

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Additional Files

Morey_2024_Supplemental_Tables_7-18-24.xlsx (103 kB)

Stuart Morey Signatory Page FINAL.pdf (298 kB)

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