Research Overview
The Ronald laboratory studies the role that genes play in a plant’s response to its environment. Our primary research focus is rice, the primary food for more than 3 billion people. We have four main research areas. Projects include the cloning and characterization of disease resistance genes, identification of pathogen produced signal molecules that interact with disease resistance gene products, biochemical analysis of disease resistance gene products and their interacting proteins, studies of the evolution of disease resistance loci, elucidation of the structure of the rice cell wall and analysis of sequences expressed during the rice defense response and cell wall formation.
1. Rice Genetics
A thorough understanding of the complex signal transduction processes in monocots requires appropriate tools, as many aspects of their development and physiology are different from those of dicots. Rice, because of its diploid genetics, small genome size, extensive genetic map, available genome sequence, and relative ease of transformation, is considered a model monocot. Therefore the structural and functional analysis of rice has broad practical implications for the other economically important cereals. Rice is one of the few higher eukaryotic genomes that have been fully sequenced. The convergence of genomic sequence, informatics, and protein-protein interaction technologies has created the opportunity to dramatically enhance our understanding of cell signaling in the cereals, using rice as a model system. Development and application of these technologies will augment traditional approaches to create higher yielding varieties of cereal species.
- Development of an oligonucleotide microarray for the rice genome
- Development of rice genome tiling microarray
- Construction of a protein interaction database for 275 rice kinases
- Specificity and control of XA21-mediated signal transduction: the role of the juxtamembrane domain, WRKY factors and a PP2C phosphatase
- Systemic acquired resistance, age-related resistance and programmed cell death
- The molecular basis for broad spectrum resistance to rice blast
2. Xanthomonas biology
It is estimated that 50% of the potential yield of the world rice crop is lost to diseases caused by bacteria, fungi and viruses. One of the most serious bacterial diseases of rice in Africa and Asia is bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo). BLB is one of the oldest recorded rice diseases and has been problematic for over a century. The genus Xanthomonas consists of 20 plant-associated species, many of which cause important diseases of crops and ornamental plants. Individual species comprise multiple pathovars, characterized by distinctive host specificity or mode of infection. Genomics is at the center of a revolution in Xanthomonas biology. Complete genome sequences are available for nine Xanthomonas strains, representing three species and five pathovars, including vascular and non-vascular pathogens of the important models for plant biology, Arabidopsis thaliana and rice. With the diversity of complete and pending Xanthomonas genome sequences, the genus has become a superb model for understanding functional, regulatory, epidemiological, and evolutionary aspects of host- and tissue-specific plant pathogenesis.
The most serious fungal disease of rice is blast caused by the fungus Pyricularia oryzae. The rice/ Xoo and blast interactions present useful genetic systems for studying interactions between two organisms and has direct relevance to the cultivation of important food crops.
3. Submergence tolerance
Environmental stresses, particularly water availability and disease, are the largest factors determining plant yields and quality. We are using genomic, proteomic and informatic tools to study rice response to submergence stress. Each year millions of small farmers in the poorest areas of the world lose their entire crops to submergence. Approximately one fourth of the global rice crop is grown in rainfed, lowland plots that are prone to seasonal flooding. These seasonal flash floods are extremely unpredictable and may occur at any growth stage of the rice crop. While rice is the only cereal crop that can withstand submergence at all, most rice varieties will die if fully submerged for too long. When the plant is covered with water, its oxygen and carbon dioxide supplies are reduced, which interferes with photosynthesis and respiration. Because the submerged plants lack the air and sunlight they need to function, growth is inhibited and the plants will die if they remain underwater for more than four days.
Our research team has identified a gene that confers submergence tolerance to rice and have introduced this gene into agronomically important varieties. The resulting rice plants are not only tolerant of being submerged in water but also produced high yields and retained other beneficial crop qualities. Development of submergence-tolerant varieties for commercial production in Laos, Bangladesh and India is now well underway. Cultivation of the new variety is expected to increase food security for 70 million of the world's poorest people, and may reduce yield losses from weeds in areas like the United States where rice is seeded in flooded fields.
4. Bioenergy
Cost efficient conversion of lignocellulosic biomass into bioethanol requires changes in cell wall characteristics and yield. The Poaceae family, represented by rice, holds great promise to the bio-fuel industry, which include all cereals and crops such as switchgrass (Panicum virgatum L.). Currently used primarily for forage and erosion control, switchgrass has recently received attention from breeders because of its potential as a bioenergy crop. There is now a tremendous opportunity to leverage genomic information from other grass species such as rice for switchgrass improvement. The Ronald lab is using a variety of approaches, together with collaborators, to investigate cell wall synthesis and function. For more information, please see our JBEI and DOE-USDA- funded projects.
5. RiceCAP
The genome, or DNA genetic code, of rice is composed of approximately 50,000 “pieces” of DNA, called genes, which control all plant traits including yield and pest resistance. The sequence information is now publicly available to rice researchers worldwide. For the rice industry to use this valuable resource effectively, rice researchers need to begin to understand the function of these genes and how they impart economically valuable attributes to commercial rice. A better understanding of these genes will enable researchers to develop a hardier and more productive rice crop.
Two attributes that have been difficult to improve through traditional plant breeding efforts are milling yield and disease resistance to sheath blight, one of the most pervasive and destructive diseases of rice worldwide. The RiceCAP project aims to develop a set of biotechnology-based tools to improve these two attributes in U. S. rice varieties. The tools being developed will help rice researchers identify genes that control these important agronomic traits as well as determine their function in the rice plant. This biotechnology toolbox will allow traditional rice breeders to address problems that they have been unable to address adequately in the past.
The RiceCAP project is a multi-institution and multi-state program with a strong research component as well as teaching and extension efforts to fully engage the rice community on the potential benefits of the overall effort. The project will advance the utility of the biotechnology information available for rice, train traditional rice breeders in the usefulness of biotechnology based tools, and educate a broader audience on the merits of such an approach to improve rice cultivars.
For a more detailed description of each project click here. You can also browse our list of selected publications and links.
