Hanah Chaudry

Date of Award

2019

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Clore, Amy

Area of Concentration

Cellular and Molecular Biology

Abstract

Fungal and bacterial endophytes live within the tissue of every plant and are beneficial to their hosts in many ways. Endophytic presence can affect plant morphology, metabolism and gene expression leading to advantages like increased abiotic stress tolerance, disease resistance and pest deterrence. Endophytic communities, which are thought to have evolved from Rhizosphere bacteria, have differing compositions in different tissues (Card et al. , 2015, (Liu et al., 2013) ). However, the development of this diversity is not well studied. The curd of cauliflower ( Brassica oleracea var. Botrytis), was used for tissue culturing because of its ability to differentiate into multiple organ types. It was found that sterilizing the curd with an aqueous solution of 0.91% sodium hypochlorite for 15 minutes, was the most effective at preventing contamination and tissue death. After culturing for 30 days, the diverse organs were harvested and used for metagenomic analysis of the bacterial endophytic communities within. In total, over 577,000 operational taxonomic units (OTUs) from 10 different bacteria phyla were present. The starting, undifferentiated curd had the most homogenous population, with the genus Trichodesmium dominant. The tissues that had diverged the most from this, in that they had the most heterogeneous bacterial communities, were the roots samples. In these samples, the genus Ralstonia was most present. The roots samples had the greatest relative abundance and diversity of bacterial endophytes based on the total OTUs and average 16S rRNA gene sequence reads. In addition, the development of chlorophyll in the curd was associated with a 4-9% increase in community diversity. The development of anthocyanin was associated with an increase in community diversity in the samples harvested from one explant, but not the other. While these results provide a snapshot view of the endophytic communities of cauliflower, more research should be done to confirm these results in planta.

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