Page Banner

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

2009 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
All milestones were either fully or substantially met during this reporting period. The research showed that by choosing the appropriately regulated plant promoter (e.g., water or heat stress responsive) and pigment inducing plant gene (e.g., transcription factor for anthocyanin production), it is potentially possible to engineer plants that will alter their pigmentation in response to specific stresses, alerting the producer that action is required. Model systems for examining post-transcriptional gene silencing in plants have been used to compare several (HcPro, P19, and AN2) viral suppressors of gene silencing. 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. Physiological and genetic analysis of plant tolerance to environmental stresses is providing information to correlate metabolite responses with whole-plant stress tolerance. To create drought-tolerant crops foreign genes were introduced into crops to improve stress tolerance. Changes in protein levels for selected pathways showed differential gene expression in response to stress in peanuts. Differences in root development as a result of the alternate furrow SDI configuration (dry furrow showed higher root occupancy than wet furrow) were identified. The impact of storage environments on cotton seedling vigor was identified. Genetic diversity in the magnitude of hydraulic lift, or the ability of the plant to transfer water from wet zones in the soil profile to drier zones through the root system was identified.


4.Accomplishments
1. Synthetic plant-functional promoters: Improving crop stress tolerances through modern biotechnology methods requires a gene delivery and regulation system that optimizes expression of beneficial transgenes. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, produced, tested, and released synthetic gene regulation systems to researchers and stakeholders. A detailed study of the function and interaction of the synthetic gene regulation system components was performed to better understand the control gene expression in plants. Part of this research has been the identification of three up-regulated and one down-regulated plant promoter elements that respond to pathogen stress. The results of this study will aid in the development of improved gene regulation systems.

2. Gene silencing and transgene function in plants: Small RNA (smRNA) molecules have recently been shown to regulate gene expression. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, have evaluated regulation of gene silencing in plants using mechanisms that viruses have developed to prevent their genes from being silenced by the plants that they infect. Gene expression levels were enhanced through the use of inhibitors of gene silencing. Understanding of the molecular processes involved is essential if we are going to be able to employ these smRNA systems to improve crop stress tolerance.

3. Visible stress reporter system: Producers make daily management decisions about their crops' health through visible cues provided by the plant. Unfortunately many of these cues appear after injury resulting in yield losses have occurred. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, are developing a genetic system that would provide the producer with simple visible cues (e.g., plant pigment production) when stresses begin to occur before the crop experiences yield reductions. Factors regulating purple pigment production and reduction have been identified. These findings will help us develop the first generation of stress reporting crops.

4. Metabolic profiling of pathways providing stress tolerance: Plants respond to environmental stresses by adjusting the amount and types of lipids, proteins, and sugars. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, are using targeted-metabolic profile analysis to identify metabolites in several biochemical pathways (lipid, protein, carbon) contributing to heat and/or drought tolerances in plants. Moderately high throughput, low-cost methods have been configured for extracting and analyzing different classes of metabolites. Currently, the potential application of this approach to screen potentially stress-tolerant germplasm and breeding lines is being tested under field condition. This approach combined with physiological and genetic analysis of plant tolerance to environmental stresses will provide sufficient information to correlate metabolite responses with whole-plant stress tolerance.

5. Improving drought tolerance in crops: Drought stress is one of the major factors that limit crop production worldwide. In order to keep crop production in pace with growing populations, more food must be produced under stressful conditions, including drought stress. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, in collaboration with scientists at Texas Tech University, are analyzing the expression of specific genes for improving stress tolerance. Our preliminary findings with transgenic cotton plants indicate that over-expressing these genes can indeed improve drought- and salt-tolerance in cotton. These findings have identified a very promising gene that can be used to improve crop production in water-limited areas.

6. Cloning of candidate genes for expression analysis and creation of a stress gene database: Crop yields are reduced annually because of water deficits and temperature extremes. One way to create drought-tolerant crops is to introduce foreign genes into crops that can improve stress tolerance. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, tested 5 candidate genes for enhanced stress tolerance or enhanced yield quality in transgenic cotton and peanut. The fiber yield of the transgenic cotton plants was significantly higher than that of wild-type cotton under both water-deficit and salt conditions. This study provides insight into specific genes for enhancing drought tolerance in crops.

7. Correlation of gene expression patterns with protein and metabolite data: Peanut yields are routinely impacted by heat and drought. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, examined the changes in protein levels for selected pathways showing differential gene expression in response to stress. Differential regulation of leaf proteins involved in a variety of cellular functions (e.g., cell wall strengthening, signal transduction, energy metabolism, cellular detoxification, and gene regulation) indicate that these molecules could affect the molecular mechanism of water-deficit stress tolerance in peanut. Subsequent metabolite analyses are underway.

8. Subsurface drip irrigation impacts root development: Cotton root developmental patterns are impacted by the method of irrigation management and may affect their ability to access surface water from rain events. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, evaluated a series of cotton varieties for root system development in field studies in response to different water applications using sub-surface drip irrigation (SDI). The results indicated that there were differences in root development as a result of the alternate furrow SDI configuration (dry furrow showed higher root occupancy than wet furrow). This information will aid in the development of new cotton varieties with enhance rooting capabilities.

9. Cotton seed storage impacts seed quality: Cotton seed storage can reduce the viability and vigor of the seed. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, evaluated the impact of storage environments on cotton seedling vigor. The study showed that storage temperature was the primary factor leading to differences in maintaining seedling vigor rather than differences in relative humidity over the two-year storage period. The results also showed that mechanically delinting the seed did not change how the seed responded to the storage locations indicating that this method of removing fibers from the seed should be a viable alternative to acid delinting in terms of preserving seed quality. This study provided the cotton seed industry information to improve cotton seed storage conditions to enhance germination and seedling vigor.

10. Water movement through roots to dry soil: Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, evaluated genetic diversity in the magnitude of hydraulic lift, or the ability of the plant to transfer water from wet zones in the soil profile to drier zones through the root system. Hydraulic lift was observed to occur, and when the values were integrated over appropriate soil depths they ranged from 11 to 32% of the corresponding daily evapotranspiration rates of 2-6 mm/day which could maintain root viability for additional water uptake when water was made available. Genetic diversity was also observed for the phenomena. These findings could lead to the development of germplasm for maintaining viable roots in zones that typically experience soil drying and root death.


6.Technology Transfer

Number of Invention Disclosures Submitted1

Review Publications
Baker, J.T., Van Pelt, R.S., Gitz, D.C., Payton, P.R., Lascano, R.J., McMichael, B.L. 2009. Canopy gas exchange measurements of cotton in an open system. Agronomy Journal. 101(1):52-59.

Gomez, M., Burow, G.B., Burke, J.J., Burow, M., Denwar, N., Simpson, C., Ramasubramanian, T., Puppala, N. 2008. Identification of peanut hybrids using microsatellite markers and horizontal polyacrylamide gel electrophoresis. Peanut Science. 35(2):123-129.

Velten, J.P., Pogson, B.J., Cazzonelli, C. 2008. Luciferase as a reporter of gene activity in plants. Transgenic Plant Journal. 2(1):1-3.

Cazzonelli, C.I., Velten, J.P. 2007. In vivo characterization of plant promoter element interaction using synthetic promoters. Transgenic Research. 17(3):437-457.

Kottapalli, K., Rakwal, R., Shibato, J., Burow, G.B., Burke, J.J., Puppala, N., Payton, P.R., Burow, M. 2008. Physiology and proteomics of the water-deficit stress response in three contrasting peanut genotypes. Plant, Cell and Environment. 32(4):380-407.

Last Modified: 10/1/2014
Footer Content Back to Top of Page