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United States Department of Agriculture

Agricultural Research Service

Research Project: CHARACTERIZATION AND ENHANCEMENT OF PLANT RESISTANCE TO WATER-DEFICIT AND THERMAL STRESSES

Location: Plant Stress and Germplasm Development Research

2010 Annual Report


1a.Objectives (from AD-416)
1)Identify and functionally characterize genes central to the adaptation of plant to water-deficit and thermal stresses. 2)Discover and/or develop germplasm enhanced for stress resistance traits. 3)Identify and characterize water-deficit and thermal stress-responding promoters for use in controlled expression of stress resistance genes and for testing of a user-friendly plant stress reporter system for crop management.


1b.Approach (from AD-416)
A multidisciplinary research approach will be utilized because of the complexity of the problems to be addressed. Genes will be identified via expression databases and mutational analyses. Physiological and molecular characterizations will be used to identify germplasm with enhanced stress tolerances. Transformational technologies will be used in the development of plants with enhanced stress tolerances and plants with stress responsive reporter genes.


3.Progress Report
In 2010, we conducted a second year field trial at 4 locations on peanut germplasm identified as stress tolerant. Year 1 results showed significantly higher yield in the selected germplasm and than two commercial check varieties grown under limited irrigation conditions. Collaborative research was completed on improved drought tolerance in cotton plants over-expressing a vacuolar proton pump. A manuscript entitled "Expression of an Arabidopsis vacuolar H+-pyrophosphatase gene (AVP1) in cotton improves drought- and salt tolerance and increases fiber yield in the field conditions" was published in Plant Biotechnology Journal. To identify genes contributing to heat tolerance in plants we evaluated the heat sensitivity of mutant Arabidopsis lines. A mutation in a specific transcription factor was identified. The relative contribution to overall heat tolerance was determined using a chlorophyll accumulation bioassay developed in our laboratory. To better understand the relationship between a mutation that enhances freezing tolerance and the impact on plant growth, a series of independent mutations in the specific gene (Eskimo 1, ESK1) previously shown to enhance freezing tolerance were investigated. The findings showed that reduced plant growth was always associated with mutations in the ESK1 gene. To effectively express and regulate transgenes that have the potential of improving plant stress resistance, it is necessary to better understand exactly how gene silencing in plants functions. We have developed a model system for examining post transcriptional gene silencing in plants and have begun quantifying and characterizing transgene silencing in plants. smRNA gene regulation has been implicated as a player in how plants respond to environmental changes and a better understanding of the molecular processes involved is essential in contending with, and potentially employing, smRNA systems in plants engineered for improved stress tolerance. As part of the planned development of molecular technology for controlling the in vivo expression of beneficial transgenes, synthetic promoters were produced, tested and released to researchers and stakeholders. A detailed quantitative analysis of the function and interaction of individual transcriptional promoter elements was also performed to better understand how different regulatory sequence elements interact to control gene expression. This work adds to a limited collection of well characterized plant promoters that are in the public domain, and provides novel insight that contributes to an improved ability to construct and employ gene regulatory systems for plant genetic engineering.


4.Accomplishments
1. Gene expression patterns can be tracked for peanuts. Peanut, being an under-represented crop in terms of genome sequencing and physical mapping, needs a comprehensive tool for dissecting complex mechanisms of development and tolerance to insects, diseases, and environmental stresses. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, developed a tool to analyze changes in the expression of 49,205 peanut genes and tested the utility of this tool on a variety of peanut tissues. This is the first large-scale, publicly available tool for determining which peanut genes are active out of all of the genes that exist within the peanut plant. The results generated by this tool will provide starting points for in-depth studies on candidate genes that can be utilized in reverse genetics to assign gene functions and identify specific molecular mechanisms of peanut response of environmental signals, developmental stages, and yield quality characteristics.

2. The color purple - Now you see it...Now you don't. Anthocyanin pigment production has long been the target of genetic and molecular research in plants due to the ease of visual detection of the red-purple pigments produced in various plant tissues. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, have identified a simple mutation that resulted in the production of a truncated gene regulatory protein. The shortened protein was found to interfere with normal anthocyanin pigment production within tobacco flower petals. This finding is important to researchers interested in how plant regulatory proteins control gene expression and represents a potential pathway to affecting and/or controlling how gene regulatory proteins function in plants.

3. Yield enhancement technology for dryland cotton. Plant growth and development can be inhibited by early season drought. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, have discovered a novel process for enhancing the growth and development of cotton under drought conditions. Application of relatively low concentrations of a naturally occurring plant hormone called a cytokinin to cotton seed or to young cotton plants increased cotton yields under rain-fed conditions. These findings provide a means of increasing dryland yields without any adverse effects on irrigated cotton production.

4. Taking a plants' temperature. Continuous measurement of plant canopy temperature is useful in both research and production agriculture settings. Industrial-quality infrared thermometers which are often used for measurement of canopy temperatures, while reliable, are not always cost effective. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, incorporated a relatively low-cost, consumer-quality infrared thermometer into a wireless monitoring system intended for use in plant physiological studies and in agricultural production settings. The results indicated that for many common uses of plant temperature data, the cost savings and ease of use associated with a low-cost wireless temperature monitoring system presented advantages over the higher-cost industrial-quality sensors, making them a viable alternative in many agricultural settings.

5. Can’t handle the heat: High temperature stress severely limits plant productivity and causes extensive economic losses in maize. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas have identified the physiological basis for heat sensitivity in selected maize lines. Their results suggest that the stability of cell membranes at high temperature plays a critical role in heat tolerance and that a specific cellular membrane lipid may play an important role in maintaining membrane thermostability, and hence heat tolerance, in maize.

6. High sugar contents in immature peanuts. In most years, peanuts from the south-central US have excellent soluble sugar levels for the food industry; however, in some growing seasons high sugar contents are a significant problem associated with roasted color variation. Scientists at the Cropping Systems Research Laboratory in Lubbock, Texas, tested the hypothesis that high sugar concentration was related to low temperature extremes. The results showed that low soil temperatures delayed peanut maturation, resulting in elevated carbohydrate levels. his study suggests that early to mid-season weather related delays in pod set may result in increased numbers of immature peanuts, and consequently higher sugar contents, at harvest.


Review Publications
McMichael, B.L., Lascano, R.J. 2010. Evaluation of hydraulic lift in cotton (Gossypium hirsutum L.) germplasm. Environmental and Experimental Botany. 68(1):26-30.

Cakir, C., Scofield, S.R., Gillespie, M.E. 2010. Rapid determination of gene function by virus-induced gene silencing in wheat and barley. Crop Science. 50(2, Suppl. S):S77-S84.

Oliver, M.J., Hudgeons, J., Dowd, S.E., Payton, P.R. 2009. A Combined Subtractive Suppression Hybridization and Expression Profiling Strategy to Identify Novel Desiccation Response Transcripts From Tortula ruralis Gametophytes. Physiologia Plantarum. 136:437-460.

Payton, P.R., Kottapalli, K.R., Rowland, D., Faircloth, W., Guo, B., Burow, M., Puppala, N., Gallo, M. 2009. Gene expression profiling in peanut using high density oligonucleotide microarrays. Biomed Central (BMC) Genomics. 10:Article 265.

Burke, J.J., Chen, J., Rowland, D., Sanders, T.H., Dean, L.L. 2009. Temperature effects on hydroponically-grown peanut carbohydrates. Peanut Science. 36(2):150-156.

Mahan, J.R., Gitz, D.C., Payton, P.R., Allen, R. 2009. Overexpression of glutathione reductase in cotton does not alter emergence rates under temperature stress. Crop Science. 49(1):272-280.

Mahan, J.R., Conaty, W., Neilsen, J., Gitz, D.C. 2010. Field performance in an agricultural setting of a wireless temperature monitoring system based on a low-cost infrared sensor. Computers and Electronics in Agriculture. 71(2):176-181.

Velten, J.P., Cakir, C., Cazzonelli, C.I. 2010. A spontaneous dominant-negative mutation within a 35S::AtMYB90 transgene inhibits flower pigment production in tobacco. PLoS ONE. 5(3):e9917.

Baker, J.T., McMichael, B.L., Burke, J.J., Ephrath, J., Gitz, D.C., Lascano, R.J. 2009. Sand abrasion injury and biomass partitioning in cotton seedlings. Agronomy Journal. 101(6):1297-1303.

Last Modified: 7/23/2014
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