- Undergraduate Education
- B.S. Michigan Technological University, 1991
- Graduate Education
- M.S. Michigan Technological University, 1993
- Ph.D. University of Kentucky, 2000
- Postdoc. Boyce Thompson Institute for Plant Research, 2001-2005
- Joined Texas A&M in 2006
Control of plant programmed cell death during plant-pathogen interactions / Algal biofuels
We study the biochemical and molecular mechanisms underlying the control of programmed cell death (PCD) in plants and how PCD is manipulated during plant-pathogen interactions. Specifically we study the interaction between tomato and Pseudomonas syringae pv. tomato (Pst) the causative agent of bacterial spot disease. Resistance to this disease is conferred by the host Pto serine/threonine protein kinase which recognizes Pst strains expressing the type III effector protein AvrPto.
PCD is induced during both resistant and susceptible plant-pathogen interactions. In the case of a resistant interaction, PCD induced by the plant, known as the hypersensitive response (HR), and acts to limit the spread of the pathogen. In susceptible plant-pathogen interactions plant PCD is induced by the pathogen after infection leading to death of the host. Studies have indicated that the genes controlling host PCD during the HR are the same genes that are manipulated by the pathogen during susceptible interactions. The difference lies in the timing of controlling the activity of these genes; HR PCD occurs within 12 hours of pathogen recognition while pathogen-induced PCD occurs several days after infection.
Many of these genes that control plant PCD are serine/threonine (S/T) protein kinase. We are interested in studying a specific class of S/T protein kinases that control PCD in plants called AGC kinases and how they are regulated in both resistant and susceptible plant-pathogen interactions. Additionally, when plants are not attacked by pathogens, PCD is a process that requires constant control so that cell death does not occur. We are looking at the signaling mechanisms and pathways employed to keep PCD under check in non-pathogen challenged plants.
Algal production of hydrocarbons as a renewable energy source
Botryococcus braunii is a colony forming microalga with individual cells of the colony held together by an extracellular matrix of liquid hydrocarbons embedded within a cross-linked hydrocarbon core. Thirty carbon (C30) triterpenoid hydrocarbons, referred to as botryococcenes, are the major matrix component associated with the B race of B. braunii. The C30 botryococcene is methylated to C34 botryococcene, the predominant botryococcene in the extracellular matrix.
The B race has attracted special attention for several reasons. One, this race can accumulate botryococcenes up to 30-40% of their dry weight. Two, caustic hydrolysis of the highly branched C34 botryococcene results in the generation of hydrocarbon fuels suitable for internal combustion engine. This caustic hydrolysis of crude B. braunii hydrocarbons yields 60 – 70% gasoline which is comparable to the yield from petroleum. Third, botryococcenes from B. braunii have been found in fossil oil deposits raising questions as to the contribution of B. braunii to oil deposits used today.
We are studying the genes involved in the biosynthesis of the C30 botryococcene hydrocarbon and the gene(s) involved in converting C30 botryococcene to C34 botryococcene with the long term goal of transferring this pathway to a terrestrial plant such as tobacco for production of high amounts of hydrocarbon fuel as a renewable source of energy.
Cornejo-Corona, I, Thapa, HR, Browne, DR, Devarenne, TP, Lozoya-Gloria, E. Stress responses of the oil-producing green microalga Botryococcus braunii Race B. PeerJ. 2016;4 :e2748.
Kim, HS, Guzman, AR, Thapa, HR, Devarenne, TP, Han, A. Cover Image, Volume 113, Number 8, August 2016. Biotechnol. Bioeng. 2016;113 (8):i.
Thapa, HR, Naik, MT, Okada, S, Takada, K, Molnár, I, Xu, Y et al.. A squalene synthase-like enzyme initiates production of tetraterpenoid hydrocarbons in Botryococcus braunii Race L. Nat Commun. 2016;7 :11198.
Miao, M, Niu, X, Kud, J, Du, X, Avila, J, Devarenne, TP et al.. The ubiquitin ligase SEVEN IN ABSENTIA (SINA) ubiquitinates a defense-related NAC transcription factor and is involved in defense signaling. New Phytol. 2016;211 (1):138-48.
Klionsky, DJ, Abdelmohsen, K, Abe, A, Abedin, MJ, Abeliovich, H, Acevedo Arozena, A et al.. Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy. 2016;12 (1):1-222.
Kim, HS, Guzman, AR, Thapa, HR, Devarenne, TP, Han, A. A droplet microfluidics platform for rapid microalgal growth and oil production analysis. Biotechnol. Bioeng. 2016;113 (8):1691-701.
Kim, HS, Devarenne, TP, Han, A. A high-throughput microfluidic single-cell screening platform capable of selective cell extraction. Lab Chip. 2015;15 (11):2467-75.
Ek-Ramos, MJ, Avila, J, Nelson Dittrich, AC, Su, D, Gray, JW, Devarenne, TP et al.. The tomato cell death suppressor Adi3 is restricted to the endosomal system in response to the Pseudomonas syringae effector protein AvrPto. PLoS ONE. 2014;9 (10):e110807.
Kim, HS, Weiss, TL, Thapa, HR, Devarenne, TP, Han, A. A microfluidic photobioreactor array demonstrating high-throughput screening for microalgal oil production. Lab Chip. 2014;14 (8):1415-25.
Gray, JW, Nelson Dittrich, AC, Chen, S, Avila, J, Giavalisco, P, Devarenne, TP et al.. Two Pdk1 phosphorylation sites on the plant cell death suppressor Adi3 contribute to substrate phosphorylation. Biochim. Biophys. Acta. 2013;1834 (6):1099-106.