Mannie Liscum

Professor of Biological Sciences

PhD, 1992 Ohio State University

liscumm@missouri.edu
573-882-2672
371E Christopher S. Bond Life Sciences Center

http://www.biosci.missouri.edu/liscum/LiscumLabPage.html

Research description

All living organisms utilize both exogenous and endogenous cues to regulate their metabolism, growth and development. Plants, given their ‘fixed in the ground’ (sessile) nature are especially sensitive and responsive to their environment and exhibit highly plastic developmental programs. Unlike animals where the body plan is established almost entirely during embryogenesis, plant form and function is mostly elaborated post-embryonically. This dominance of post-embryonic patterning and growth affords plants the plasticity they need to modify their growth, morphology and behavior to even subtle and rapid changes in their environment. Because environmental inputs are numerous and ever changing, responsiveness of an organism is highly integrated, where multiple input signals are ‘sorted’ and transduced in an efficient manner to give rise to proper adaptive responses. Our laboratory is interested in understanding such integrated signal-response systems from molecules to functional ecology, and employ Arabidopsis thaliana as a model for most of our studies.

Two adaptive responses we are particularly interested in are: 1) phototropism, or the directional ‘movement’ of plant organs towards or away from direction light, and 2) prevention of polyspermy during plant reproduction.

Phototropism is a classic example of plant ‘movement’ that is both robust and rapid, and is genetically amenable in Arabidopsis. Our studies have shown that the plant utilizes multiple photosensory pathways to monitor the light environment, and that these pathways are integrated with a number of endogenous hormone response pathways to elicit an adaptive phototropic response. Our current research foci on phototropism include: understanding how the primary phototropic photoreceptor, phototropin 1, initiates signal transduction; unraveling the role of protein ubiquitination in early signaling events; determining the transcriptional outputs of the signaling process and how their encoded proteins affect physiological outputs; developing a 3D temporal-spatial map of the phototropic response system in planta; and elucidating how phototropic responses impact plant ecology and evolution under natural conditions.

Plants, like animals, reproduce sexually and must therefore control gamete interactions to produce a proper zygotic genome. One mechanism by which this is accomplished is to prevent polyspermy, or fertilization of a single egg by multiple sperm. While much is known about how polyspermy is prevented in animal systems, little is known mechanistically about this process in plants. In a collaborative project with Dr. Steve Alexander (MU-Biological Sciences) we have recently found that in the absence of particular lipid metabolites, whose production are dependent upon enzymes encoded by the male genome, the block to polyspermy does not occur. We are currently focused on understanding how such metabolites affect the communication between male and female genomes during normal and aberrant fertilization at both molecular and cellular levels.

Selected publications

Galen, C., Rabenold, J.J. and Liscum, E. 2007. Functional ecology of a blue light photoreceptor: effects of phototropin-1 on root growth enhance drought tolerance in Arabidopsis thaliana. New Phytologist 173: 91-99.

Galen, C., Rabenold, J.J. and Liscum, E. 2007. Addendum: Light-sensing in roots. Plant Signaling & Behavior 2: 106-108.

Pedmale, U.V. and Liscum, E. 2007. Regulations of phototropic signaling in Arabidopsis through phosphorylation state changes in the phot1-interacting protein NPH3. Journal of Biological Chemistry 282: 19992-20001.

Lariquet, P., Schepens, I., Hodgson, D., Pedmale, U.V., Alanso, J.M., Ecker, J.R., Liscum, E., and Frankhauser, C. 2006. PKS1 (phytochrome kinase substrate 1) is a phototropin 1 binding protein required for phototropism. Proceedings of National Academy of Sciences USA, in press.

Esmon, C.A., Tinsley, A.G., Ljung, K., Sandberg, G., Hearne, L., and Liscum, E. 2006. A gradient of auxin and auxin-dependent transcription precedes tropic growth responses. Proceedings of the National Academy of Sciences USA, 103: 236-241.

Selected national/international awards and honors

Elected Fellow - AAAS

New Investigator Award - American Society for Photobiology

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