Project Number: 5335-21000-026-00
Project Type: Appropriated

Start Date: Mar 24, 2008
End Date: Mar 23, 2013

Objective:
Objective 1: Define the contribution of the circadian clock to plant osmotic and salt stress responses using Arabidopsis as an initial model system. Objective 2: Characterize the contribution of the circadian clock to transcriptional control networks in cereals, using Oryza sativa as a model. Sub-objective 2.A.: Define the circadian transcriptome of Oryza sativa. Sub-objective 2.B.: Identify cis-regulatory elements upstream of co-expressed circadian genes. Objective 3: Determine the function of maize photoperiodism genes identified as naturally occurring alleles in maize recombinant inbred lines. Objective 4: Assess the feasibility of high-throughput screening of maize seedlings or plants for circadian phenotypes as a prelude to screening large RIL populations for circadian quantitative trait loci (QTL).

Approach:
Maize is an important crop as well as a model organism for other cereals such as sorghum, barley, rice and wheat. Our long term goal is to identify and characterize the activity of maize genes involved in plant production including tolerance to stressful growth conditions and regulation of flowering time. Recent work in model systems demonstrates that the circadian regulation of physiological activities is required for optimal plant growth and for tuning of responses to environmental cues. A comprehensive understanding of the circadian system in cereals is lacking; therefore, this proposal seeks to define the maize circadian system and assess the circadian oscillator¿s contribution to important agronomic traits. Known circadian mutants will be tested for their response to salt and osmotic stress. Genes under circadian regulation in cereals will be identified by expression profiling, and this information used to computationally predict regulatory DNA elements that contribute to circadian gene expression. Reverse genetic approaches will evaluate the role of candidate photoperiodism genes in determining the timing of maize flowering. Maize inbreds and recombinant inbred lines will be analyzed for natural variation in overt circadian rhythms. DNA sequences, genes, mutants, and inbred lines identified here provide two types of tools: a better understanding of fundamental processes in environmental responses and targets that can be used to improve crop productivity. Formerly 5335-21000-025-00D (4/08). BSL-1; 9/6/07.