Date of Award

12-2013

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant Sciences

Major Professor

Charles N. Stewart

Committee Members

Brandon Horvath, Xong-Ming Chen

Abstract

Currently the platforms for wide-area detection of environmental contamination are limited. Therefore, there is interest in developing new platforms, especially for use in crop plants to detect and report the presence of biotic and abiotic stress agents. A biosensor uses a biological organism or substrate to detect the presence of an elicitor (i.e., heavy metal, TNT, or bacteria). The foundational groundwork to create biosensors in transgenic plants exists. The creation of bacterial phytosensing transgenic tobacco containing an orange fluorescent protein (OFP) reporter driven by synthetic pathogen-inducible promoters provides a fluorescent signal when infected with phytopathogens for earlier detection in the field.

This thesis research performed time-course analysis of field grown transgenic phytosensing tobacco plants infected with Pseudomonas phytopathogens. Some of the phytosensors responded in predictable ways to a suite of treatments, with more than 2-fold of expression of the OFP reporter driven by two different salicylic acid inducible motifs, SARE and PR1. Specifically, transgenic lines containing synthetic promoters with salicylic acid inducible cis-acting regulatory elements showed earlier OFP fluorescence induction by phytopathogen treatments (within 48 hours) than transgenic lines harboring other synthetic promoters; such as the synthetic promoters containing ethylene inducible cis-acting regulatory elements (ERE) which induced OFP fluorescence after phytopathogen treatment only at 72 hours post inoculation. Transgenic lines harboring the OFP reporter driven by synthetic promoters containing defense-related cis-acting regulatory elements were indicative of plant defenses during phytopathogen interactions. Results reported here indicate the functionality of phytosensors in the field that could play a role in presision agriculture in the future.

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