Degree Type

Thesis

Date of Award

2015

Degree Name

Master of Science

Department

Genetics, Development and Cell Biology

Major

Molecular, Cellular, and Developmental Biology

First Advisor

Ling Li

Second Advisor

Eve S. Wurtele

Abstract

Plants have to deal with environmental insults as they cannot move to escape from stressful conditions. To do so, they have evolved novel components that respond to the changing environment. The Qua Quine Starch (QQS) gene is an Arabidopsis-specific orphan gene that connects primary metabolism and adaptation to environment changes. AT1G64360, which we term an SAQR (Senescence-associated and QQS-related) gene, respond to oxidative stress. Here, we show that SAQR is up-regulated in high-starch QQS-RNAi mutants. Bioinformatics analyses indicates that SAQR is unique to six species within the family Brassicaceae; the gene may have arisen about 20 million years ago (MYA). Meta-analysis of public microarray data, in combination with histochemical experiments using transgenic Arabidopsis SAQR promoter-GUS lines, indicate that SAQR’s expression is correlated with expression of genes involved in senescence, defense, and stress responses. SAQR expression increases in leaf vasculature as tissues mature and senesce. SAQR expression is expression is not increased in true leaves under experimentally-induced senescence of thirty day-old plants. However, SAQR expression increases in cotyledons of seven day-old seedlings in response to experimentally-induced senescence. Furthermore, starch accumulation is increased in the leaves of transgenic SAQR-overexpression lines, and conversely starch levels are decreased in a T-DNA SAQR knockout line. Levels of metabolites and transcripts involved in biotic and abiotic stress responses and chlorophyll metabolism are altered in these T-DNA knockout mutants. These data may imply changes to processes that occur in senescent leaves. SAQR may function in the QQS network, playing a role in its integration of primary metabolism and adaptation to internal and environmental changes, specifically those that affect the process of senescence.

Copyright Owner

Dallas Christopher Jones

Language

en

File Format

application/pdf

File Size

111 pages

S1_SAQRGeneAlignment.rtf (288 kB)
Supplementary Figure S1 - SAQR Homolog Alignments

TS3_SAQRGeneCorrelation.xlsx (30 kB)
Supplementary Table S3 - SAQR-coexpressed Genes

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