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Understanding Plant Defense Strategies: Interplay Between Traditional Botanical Tools and Modern Analytical Approaches

Mena-Ali, Jorge [1], Kariyat, Rupesh [2], Mescher, Mark [2], DeMoraes, Consuelo [2], Stephenson, Andrew G [3].

Effects of inbreeding and herbivore damage on gene expression in Solanum carolinense.

Our previous studies have shown that inbreeding adversely affects plant resistance to herbivores in Solanum carolinense. We use tomato microarrays to assess changes in gene expression levels in response to breeding and herbivory. Two rhizome cuttings were regrown from each of two inbred and two outbred plants from each five families. One ramet served as the control and one ramet was subjected to 6-8 hours of herbivory by one third instar Manduca sexta larva and then leaf samples were harvested for microarray analysis. The resulting data were analyzed using PVCA, a modified PCA analysis that employs partial regression, to assess the relative contributions of each factor (Family, Breeding, Treatment) and their 2-way interactions on gene expression. Monte Carlo simulations were used to examine significance of the expression patterns. These analyses reveal that the model explained > 80% of the total variance in gene expression across the 40 microarrays and that all three main effects and two interactions significantly affected expression. Genes that were up or down regulated significantly were compared to UniPROT (protein database) for a determination of their function, and then categorized into defense, housekeeping, or growth gene ontologies (GOs). 1220 genes (12%) out of 10,210 genes were functionally annotated and 595 of these genes (49%) were differentially regulated in the damaged plants compared to control plants. Of the 595 differentially expressed, annotated genes, 320 (54%) were categorized primarily as growth-related genes, 234 (39%) were classified under housekeeping GOs, and 41 (7%) were categorized as defense-related genes. All GOs have more genes upregulated by herbivore damage than downregulated. Three families have no downregulated defense genes. Across all families, outbred plants had similar expression profiles in terms of GO categories and the direction of expression. In contrast, gene expression among inbred plants was much more variable in terms of both the direction of expression and GO categories. This finding suggests that inbred plants may lack some ability to regulate their responses to herbivory and may be upregulating growth and housekeeping genes that are not directly associated with an appropriate damage response and downregulating some defense related genes that are associated with an appropriate damage response. This lack of a directional coordinated response by inbred plants could be due to homozygosity of deleterious alleles and/or epigenetic modifications caused by inbreeding that result in the well-documented reduced resistance to herbivores.


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1 - Franklin and Marshall College, Department of Biology, Lancaster, PA, 17604, USA
2 - Eth Zurich, Biocommunication & Entomology, Lfo g 22, Schmelzbergstrasse, Zurich, ZR, 8092, Switzerland
3 - Pennsylvania State University, Department Of Biology, 208 MUELLER LAB, UNIVERSITY PARK, PA, 16802, USA

Keywords:
Inbreeding
plant-insect interactions
differential expression
Herbivory
Gene regulation
induced defenses.

Presentation Type: Symposium Presentation
Session: SY07, Understanding plant defense strategies: Interplay between traditional botanical tools and modern analytical approaches
Location: Chatham Ballroom - B/Savannah International Trade and Convention Center
Date: Tuesday, August 2nd, 2016
Time: 1:45 PM
Number: SY07002
Abstract ID:121
Candidate for Awards:None


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