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Gene expression analyses help elucidate positive selection in cultivated crops and early seedling responses to thiamethoxam and neighbouring turf grass

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Title: Gene expression analyses help elucidate positive selection in cultivated crops and early seedling responses to thiamethoxam and neighbouring turf grass
Author: House, Megan
Department: Department of Plant Agriculture
Program: Plant Agriculture
Advisor: Lukens, Lewis
Abstract: This thesis investigates the role of gene expression in crop evolution and crop responses to environmental variation. It applies both retrospective and experimental approaches to examine how changes in gene expression contribute to plant improvement. Using a retrospective approach, I identified genes whose regulatory alleles were selected during the breeding of elite rice varieties. Selection for groups of genes with shared attributes likely altered oxidative stress responses and amylase activity. I also identified 31 genes that have strong-acting trans regulatory factors and may have been selected for increased or decreased expression in rice breeding. In maize, I then used a high-throughput sequencing approach to identify candidate genes from seedlings that have a transcriptional response to experimentally manipulated weed competition (turf grass). Weed competition altered transcript abundance of 102 genes. Gene function annotation indicates that genes related to carbon metabolism, ROS-scavenging, hormone signalling and defence are involved in the early response of maize to the weed treatment. With the wide-use of neonicotinoid insecticides, I was also interested if thiamethoxam, a component of a popular insecticide used for maize, has an effect on seedling response to weeds. I tested for an interaction between seedling response to weeds and the thiamethoxam treatment, and found that thiamethoxam affects the response of genes involved in photosynthesis, defense, and hormone signalling. I believe that candidate genes from both approaches will be useful for future breeding efforts.
URI: http://hdl.handle.net/10214/9475
Date: 2016-01


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