Grant Information
| Knowledge Area | Subject of Investigation | Field of Science | Percent |
|---|---|---|---|
| 212 - Pathogens and Nematodes Affecting Plants | 999 - Citrus, general/other | 1100 - Bacteriology | 50% |
| 212 - Pathogens and Nematodes Affecting Plants | 999 - Citrus, general/other | 1040 - Molecular biology | 25% |
| 212 - Pathogens and Nematodes Affecting Plants | 999 - Citrus, general/other | 1160 - Pathology | 25% |
Citrus production is one of the most important agricultural economic activities in the United States and around the world. However, the citrus industry has been facing severe challenges from HLB, one of the most destructive citrus diseases and the single most vicious and debilitating disease that is responsible for the destruction of hundreds of million trees in major citrus growing areas of the world where the disease has been endemic. From 2006 to 2010, HLB caused an approximately $4.5 billion loss in Florida. This number has increased and will keep increasing due to lack of effective detection and management methods. To date, HLB incidence has been reported in all major citrus growing states including Texas, Arizona and recently in California, making it the major threat to the viability of the entire U.S. citrus industry. HLB has caused tremendous economic damage; and all infected commercial citrus industries continue to decline owing to inadequate disease control methods. HLB is especially difficult to manage because the causative pathogen Candidatus Liberibacter (a bacterium) is transmitted by prolific insect vectors and resides in the plant vascular systems. Since there is no cure for HLB once trees are infected, early detection becomes extremely important for disease management. However, detection of Ca. Liberibacter is notoriously difficult due to the sporadic distribution and low titer of the pathogens in the infected trees. Therefore, robust diagnostic methods and novel disease management strategies are urgently needed. The main purpose of this study is to enhance the detection and control of HLB through our research on pathogen effectors, which are secreted from the pathogens into host tissues for the benefit of infection. After being secreted from the pathogen cells, these effectors are dispersed throughout the infected trees along with the vascular flow; therefore, they can be used as detection markers for HLB at an early infection stage. We will generate antibodies that can bind to effectors produced by HLB pathogen and develop accurate and simple diagnostic methods for field surveys. This is important because the infected trees can be removed before they can serve as sources for the infection of other trees. Furthermore, we will use effectors as "probes" to identify key components in citrus for HLB development. Pathogens rely on the functions of effectors to defeat plant defense and acquire nutrients. We will study the citrus proteins that are targeted by HLB pathogen effectors. Identification of the specific processes in citrus that are attacked by the pathogen will reveal key information on HLB pathogenesis and set the foundation to develop novel, effective management strategies to protect young plantings from HLB and improve the longevity of HLB-infected trees.
The main goal of my research program is to understand pathogenesis of plant diseases caused by bacterial and other microbial pathogens. This project focuses on the highly destructive citrus disease Huanglongbing (HLB), which is associated with the bacterium pathogen Candidatus Liberibacter. The entire U.S. citrus industry is at risk from HLB. However, robust early detection protocols as well as adequate control methods are not available at this time. This project will directly address these urgent needs from the citrus industry by pursuing the following three objectives:
Expected Outputs: In the short term, we will generate antibodies that will be used to efficiently detect the HLB pathogen Ca. Liberibacter. These antibodies will immediately benefit the citrus industry by providing accurate and economical detection methods for this severe disease. In the long-term, we will uncover key processes and/or functions in HLB development by identifying the citrus targets of Ca. Liberibacter effectors. This knowledge will advance the understanding of HLB pathogenesis and guide the development of sustainable disease control methods. This knowledge will be instrumental for the development of sustainable control strategies. For example, this information will provide mechanistic insights to guide the on-going efforts of generating citrus lines that are HLB-resistant/tolerant. Chemical treatments can also be developed to block the interactions between effectors and their targets, which will lead to enhanced resistance to HLB. Since effectors are essential virulence proteins produced by a broad range of pathogens, this project will also provide important implications on the pathogenesis of other endemic and invasive diseases of economically important crops. From the perspective of education, this program serves as an excellent training ground for postdoc, graduate and undergraduate students. The PI will incorporate the proposed research and findings into her teaching activities, which will enhance the learning outcomes and promote students interests into scientific research. New findings will be disseminated through conference proceedings, journal articles, seminar presentations and other outreach activities of the PI.
This project is a multidisciplinary program employing a combination of genetics, genomics, biochemistry and cell biology approaches, in addition to the traditional plant pathology techniques. Effectors function inside the host tissues independent of the living pathogen cells, therefore, this project is not limited by the long-standing challenge of growing the HLB-associating bacterium in artificial media. The most important technique of this project is yeast two hybrid (Y2H) screen, which will be used to identify the effector targets in citrus. The PIs laboratory has extensive experience on the research of effector functions in plant hosts. Other tools for the follow-up characterization of effector-host target interactions are also routinely used in the laboratory. Furthermore, the PI has established collaborations with a CE specialist Georgios Vidalakis and other groups working on more applied perspective of HLB in Florida and California, who will facilitate the transformation of the acquired knowledge from this project to applications that directly benefit the industry. The impact of this project can be evaluated by the development of new antibody-based diagnostic methods for HLB, publications in high-impact journals, invited presentations by the PI and other participants of this project, and successful acquisition of extramural research funding.
Target Audience
This project reaches out to the research community in plant pathology and microbiology as well as growers in the citrus industry. Citrus bacterial diseases including Huanglongbing (HLB) and citrus stubborn disease (CSD) are major threats worldwide. Using effectors as probes, this project provides mechanistic insight as well as near-term applications. The results from this research have been disminated through publications, conference presentations, research seminars, and classroom lectures given by the PI. Wenbo Ma teaches the undergraduate course (Introductory Microbiology, 240 students) and the graduate courses (Bacterial Diseases, and Microbial Genetics) every year at UCR
Changes / Problems
Nothing Reported
Training & Professional Development
This project supported the training and research activities of one postdoc (Deborah Pagliaccia), one graduate student (Kelley Clark) and one undergraduate student (Cindy Nguyen).
Dissemination Streams
Results from this project have been disseminated through journal articles and presentations by the PI and members in her group in research and grower conferences.
Next Reporting Steps
Nothing Reported