Title page for ETD etd-01212010-141508


Type of Document Dissertation
Author Batlang, Utlwang
Author's Email Address ubatlang@vt.edu
URN etd-01212010-141508
Title Identification of Drought-Responsive Genes and Validation for Drought Resistance in Rice
Degree PhD
Department Crop and Soil Environmental Sciences
Advisory Committee
Advisor Name Title
Parrish, David J. Committee Co-Chair
Pereira, Andy Committee Co-Chair
Ervin, Erik H. Committee Member
Fike, John Herschel Committee Member
Grene, Ruth Committee Member
Veilleux, Richard E. Committee Member
Keywords
  • water use efficiency
  • rice
  • maize
  • HYR gene
  • drought resistance
  • drought stress
Date of Defense 2010-01-05
Availability unrestricted
Abstract
Drought stress was studied in rice (Oryza sativa) and maize (Zea mays) to identify drought-responsive genes and associated biological processes. One experiment with rice examined drought responses in vegetative and reproductive tissues and identified drought-responsive genes in each tissue type. The results showed that brief periods of acute drought stress at or near anthesis reduced photosynthetic efficiency and ultimately lowered grain yield. Yield was reduced as a result both of fewer spikelets developed and of lower spikelet fertility. Affymetrix arrays were used to analyze global gene expression in the transcriptomes of rice vegetative and reproductive tissue. Comparative analysis of the expressed genes indicated that the vegetative and reproductive tissues responded differently to drought stress.

An experiment was conducted with maize, using GS-FLX pyrosequencing to identify differentially expressed genes in vegetative and reproductive tissues; and these results were compared with those from the just-described rice transcriptome. Some of the drought-responsive genes in the maize reproductive tissue were validated by quantitative real time polymerase chain reaction (qRT-PCR). The differentially expressed genes common to both maize and rice were further analyzed by gene ontology analysis to reveal core biological processes involved in drought responses. In both species, drought caused a transition from protein synthesis to degradation, and photosynthesis was one of the most severely affected metabolic pathways.

In a validating experiment, a drought-responsive transcription factor found in rice and dubbed HIGHER YIELD RICE (HYR) was constitutively expressed in rice, and the transgenic HYR plants were studied. Under well-watered conditions, the HYR plants developed higher rates

of photosynthesis, greater levels of soluble sugars (glucose, fructose, and sucrose), more biomass, and higher yield. They also exhibited a drought-resistant phenotype, with higher water use efficiency, photosynthesis, and relative leaf water content under drought stress. Taken together, these studies demonstrate the potential value of newer technologies for identifying genes that might impart drought resistance and for using such genes to make crops more productive either in the presence or in the absence of drought stress

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