Document Type

Thesis - University Access Only

Award Date

2007

Degree Name

Master of Science (MS)

Department / School

Biology

Abstract

The native grape, Vitis riparia, is a woody perennial vine that cycles from active growth to dormancy to survive winter conditions. Once dormant, the overwintering buds require a certain amount of chilling (hours below 7°C) before they will break dormancy and begin to grow. To understand the molecular mechanism of chilling in the overwintering buds, we utilized custom cDNA microarrays to examine the differential gene expression during the acquisition of chilling. Bud tissue exposed to 4 °C was collected at 0, 500, 1000, 1500, and 2000 hours of chilling. Three-node cuttings collected concurrently with buds were exposed to growth conditions (25°C with constant lights) to monitor depth of dormancy. Complete (100%) bud break was achieved after 1500 hours of chilling. However, the rate of bud break was significantly more rapid after 2000 hours of chilling, indicating complete fulfillment of the chilling requirement. Microarray data analysis was performed using the R software package LIMMA. A total of 456 genes were significantly expressed at p-value<0.001 when the 1000, 1500, and 2000 hour time points were compared to 500 hours of chilling. An increasing number of genes were expressed with increased accumulation of chilling. A core group of 25 genes were consistently down-regulated at all time points. The majority of genes both up- and down-regulated were involved in cell defense and stress response, metabolism, genetic information processing, and cell structure. Dehydrin, glutathione S-transferase, metallothionein, pathogenesis-related protein, peroxidase, xyloglucan endotransglycosylase, and cyclase were chosen as candidate genes for verification by real-time PCR. The relative expression of all but one candidate gene correlated with the microarray data. Transcriptomic profiles obtained from this study will contribute to the understanding of the molecular mechanisms involved in the grape plant's fulfillment of its chilling requirement and preparation for release from dormancy.

Library of Congress Subject Headings

Grapes -- Genetics

Grapes -- Growth

Gene expression

Format

application/pdf

Number of Pages

107

Publisher

South Dakota State University

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