Location: Genetic Improvement for Fruits & Vegetables Laboratory
Project Number: 8042-21000-305-019-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2023
End Date: Aug 31, 2026
Objective:
Plant response to Thaxtomin, the toxin active in common scab disease, can be variable depending on the host genetic background. Additional research is required to identify and characterize the genes that elicit plant response to Thaxtomin.
1. Characterize and manipulate potato genes involved in response to the phytotoxin Thaxtomin for broad common scab disease control.
2. Identify Streptomyces genes putatively involved in plant virulence and characterize their role through functional genomics.
Approach:
1. Multiple genes that have been identified in model plants for altering response to the toxin Thaxtomin have been identified in potatoes. The potato orthologs will be overexpressed in the model plant systems (Arabidopsis and radish) to confirm role in Thaxtomin response. Following, the genes will be knocked out or overexpressed in potato and transgenic plants tested for altered Thaxtomin response and resistance to common scab infection in greenhouse pot assays. For one of the target genes, a plasma-membrane-bound gene involved in auxin signal transduction, a truncated version of the gene is necessary for conferring extreme Thaxtomin tolerance without impacting plant growth in model plants. The same truncation variant will be created in potato through targeted intragene disruption using CRISPR-mediated gene editing. Additionally, expression of truncated variants will be tested for Thaxtomin tolerance and common scab resistance in both wildtype and mutant knockdown lines to confirm the best genetic background for conferring extreme Thaxtomin tolerance and common scab resistance. Other genes associated with the auxin signaling transduction gene will also be considered for their role in Thaxtomin sensitivity/tolerance first in model plant systems and then in potato.
2. Genome wide association studies will be performed on a large collection of Streptomyces genomes with variable virulence on potato to identify genes associated with virulence. Identified genes will either be overexpressed using standard vectors with constitutively expressed Streptomyces promoters or knocked out for functional testing. Streptomyces gene knockouts are not established in the group and multiple approaches will be considered including homologous recombination gene disruption vectors and CRISPR-mediated vectors for introducing early frame shifts. Functional testing will include measuring Thaxtomin toxin production in multiple growth conditions, virulence on radish, and virulence on potato in greenhouse pot assays.
