Geminiviruses are plant pathogens that seriously threaten agricultural crops worldwide. Obtaining new information about interactions between geminiviruses and plants will advance our understanding of normal physiological processes in plants, and how viruses exploit the host to induce infection. The investigators will identify and characterize host genes involved in geminivirus pathogenesis. Tomato golden mosaic and Cabbage leaf curl viruses produce a protein, AL2, which interacts with a host protein, PPD2. The overriding goal of this proposal is to therefore characterize the interaction between AL2 and PPD2 and define its role in suppressing host defenses, which is currently unknown. This project will use molecular, biochemical, genomic and genetic approaches to achieve this objective. We expect to characterize the role of the AL2::PPD2 complex in activating host defenses, and to identify host genes activated by this complex. The broader impacts of this research include providing information leading to the identification of networks of genes involved in host defense. This is expected to provide a basis for new resistance strategies, based on disrupting interactions critical for viral pathogenesis, which could translate into developing crops resistant to geminivirus disease. This would have a direct economic benefit to the local farmer, and will be important for decreasing the use of harmful pesticides and increasing the food production needed to sustain a growing human population. This project will provide training opportunities for undergraduate and graduate students, and a post-doctoral scientist, to gain knowledge in current topics related to plant molecular virology. UTSA demographics suggest one or more of these will be members of historically underrepresented groups. Opportunities for collaborations with scientists in Mexico and Central America may arise, where geminivirus diseases are devastating to local economies, and help facilitate exchange opportunities for both faculty and students.
Intellectual Merit: Geminiviruses are plant pathogens that seriously threaten agricultural crops across the Southern US, where crop failure can reach 100% and economic losses reach into millions $US. Increasing our fundamental understanding of viral plant diseases in general, and geminiviruses in particular, is critical for acquiring greater knowledge of the mechanisms by which geminiviruses manipulate the host to facilitate viral infection. Experiments that were conducted during the project period were designed to identify and characterize the ways in which geminiviruses interact with host plants to cause disease. The major outcomes for the research conducted during the project period are all associated with the manipulation of the plant host during viral infection. Specifically we have determined that a single viral protein induces changes in the host that establish an environment conducive to infection. Tomato golden mosaic virus (TGMV) and Cabbage leaf curl virus (CaLCuV) produce a small multifunctional protein, AL2, that functions to regulate transcription and suppress host defenses. During the project period we have established that AL2 interacts with at least two host factors, PPD2 and TCP24, and that the interaction appears to be conserved amongst different virus::host combinations, which has implications for the long-term development of broadly applicable strategies to counteract geminivirus disease progression. When PPD2 levels were increased virus infection was reduced, suggesting that PPD2 may play a role in host defenses against geminivirus infection. We have also been able to identify networks of host genes that appear to be influenced by geminivirus AL2 protein. One of the more significant findings has been the discovery of genes involved in pathways that respond to biotic stresses, including viral infection. One of these pathways is autophagy, which plays a number of important roles in cells including the plant antiviral immune response. Another significant finding is that geminviruses appear to manipulate RNA silencing, a host defense mechanism that results in specific degradation of viral RNA, through association with the host factor rgsCaM. We have also been able to establish a potential link between RNA silencing and autophagy, which opens up an exciting new avenue of research. This work has resulted in the publication of three manuscripts and the presentation of this work at numerous scientific meetings at the local, regional, national and international level. Broader impact: First, this project allowed me to train a post-doctoral scientist, and students at both the undergraduate and graduate level. Several of these were members of historically underrepresented groups and included many women who are underrepresented in the sciences. Support by NSF for this project allowed me to expand my ongoing research program, and provided specific research opportunities for students who gained knowledge in current topics related to plant molecular virology. This experience has expanded their knowledge and helped to prepare them for careers in the sciences. Working on this project has provided the necessary background for two undergraduate students to enter Masters programs and for two Masters students to enter doctoral programs. Second, this project has the broader impact of identifying potential targets that may provide the basis for the development of novel resistance strategies. Geminivirus diseases have been reported in field crops in areas surrounding San Antonio, and my laboratory has been involved in diagnostic work identifying potential geminivirus infections. Continuing our work on how geminiviruses influence plant defense responses could provide a basis for translation of research into the development of crops that are resistant to geminivirus disease. This would have a direct economic benefit to the local farmer. Together this will be important for decreasing the use of harmful pesticides and increasing the food production needed to sustain a growing human population.
