Faculty - Stellos Tavantzis
Professor of Plant Pathology and Cooperating Professor of Biochemistry and Microbiology
Ph.D., Pennsylvania State University, 1980
Research topics: Molecular genetics of virulence in plant pathogenic fungi; biological control of fungal plant pathogens
Molecular genetics of hypovirulence in plant pathogenic fungi; functional genomics for identification and characterization of genes involved in regulation of virulence in the basidiomycete Rhizoctonia solani.
The long-term goal of my work is the biological control of a cosmopolitan, soil-borne plant pathogen, Rhizoctonia solani. Species of Rhizoctonia cause economically important diseases on most of the world’s major field and vegetable crops, fruit and forest trees, turfgrasses, and ornamental plants. Thus, characterization of genetic factors regulating virulence in R. solani could have a significant impact on a wide spectrum of plant related human endeavor.
My research group has shown that particular double-stranded RNA (dsRNA) genetic elements are associated with a dramatically decreased disease-producing capacity (e.g., hypovirulence) in R. solani. Sequencing analysis of these dsRNA’s suggested that they carry an RNA polymerase gene which allows them to replicate in the host cell, but most importantly they carry nucleotide sequences that are genetically related to genes involved in different metabolic pathways. Sequencing analysis of a hypovirulence-associated dsRNA (M2) has enabled me to put forward the following hypothesis: The M2 dsRNA down-regulates the shikimic acid (shikimate) pathway, which is responsible for the synthesis of the aromatic amino acids (AAA). R. solani produces a “toxin” (phenyl acetic acid, PAA) associated with the rhizoctonia disease syndrome in potato. PAA is a derivative of one of the AAA, phenylalanine. Thus, down-regulation of AAA biosynthesis leads to a decreased production of PAA and, in turn, to a diminished degree of pathogenicity (hypovirulence).
It appears that dsRNAs in fungi (and in other organisms) are involved in gene regulation of the host cell. My research program revolves around this hypothesis. Knowledge gained in this area will lead to the development of biocontrol-based strategies of plant disease management that will fulfill the need for sustainable and nonpolluting agricultural practices. Our project is part of a multifaceted, worldwide effort aimed at making agriculture more sustainable, and congruent with the ever-growing societal aspiration to nurture the environment in which we live.
- Liu C, Lakshman DK, Tavantzis SM. 2003. Quinic acid induces hypovirulence, and expression of a hypovirulence-associated double-stranded RNA in Rhizoctonia solani. Current Genetics 43:103-111
- Liu C, Lakshman DK, Tavantzis SM. 2003. Expression of a hypovirulence-causing double-stranded RNA (dsRNA) is associated with up-regulation of quinic acid pathway, and down-regulation of shikimic acid pathway in Rhizoctonia solani. Current Genetics 42:284-291
- Tavantzis, S. M. 2001. dsRNA genetic elements: Concepts and applications in Agriculture, Forestry and Medicine. 304 p. CRC Press LLC, Boca Raton, FL.
- Tavantzis, S. M., Lakshman, D. K. and Liu, C. 2001. Double-stranded RNA Elements Modulating Virulence in Rhizoctonia solani in DsRNA Genetic Elements: Concepts and Applications in Agriculture, Forestry, and Medicine, pp. 191-201. Ed. S. M. Tavantzis, 304 p.CRC Press LLC.
- Strauss, E. E., Lakshman, D. K., and Tavantzis, S. M. 2000. Molecular characterization of the genome of a partitivirus from the basidiomycete Rhizoctonia solani. Journal of General Virology 81:549-555.
- Jian, J., Lakshman, D. K., and S. M. Tavantzis. 1998. A virulence-associated 6.4-kb dsRNA from Rhizoctonia solani is phylogenetically related to plant bromoviruses and electron transport enzymes. Molecular Plant-Microbe Interactions 11:601-609.
- Lakshman, D. K., Jian, J., and Tavantzis, S. M. 1998. A novel mitochondrial double-stranded RNA found in a hypovirulent strain of Rhizoctonia solani occurs in DNA form, and is phylogenetically related to the pentafunctional AROM protein of the shikimate pathway. Proceedings of the National Academy of Sciences (USA) 95:6425-6429 .
- Jian, J., Lakshman D. K., and Tavantzis, S. M. 1997. Association of distinct double-stranded RNAs with enhanced or diminished virulence in Rhizoctonia solani infecting potato. Molecular Plant-Microbe Interactions 10:1002-1009.