GravitropisM

To gain a unique perspective on the well-studied process of gravitropism, we focus on the Gravity Persistent Signal (GPS) response as a means to dissect cell signaling in Arabidopsis (Fukaki et al., 1996).  At cold temperatures (4°C), Arabidopsis inflorescence stems do not respond to gravity due to an inhibition of auxin transport (Nadella et al., 2006).  However, when a plant is subjected to a 90° gravistimulation at 4°C, and subsequently returned to room temperature in a vertical orientation, the inflorescence stem displays a transient bending in the direction that would have been “up” when it was oriented horizontally in the cold.  The bottom line is that a plant ends up bending to the side at room temperature after a gravistimulation in the cold.  This is referred to as the Gravity Persistent Signal (GPS) response.  It is thought to be caused by a buildup of signaling proteins and secondary messengers during the cold treatment that have no outlet without the ability to transport auxin.  Previous work suggests that the GPS process is ideal for analyzing the gravitropic pathway in a simplified system, allowing for the discovery of signaling components that may otherwise have undetectable mutant phenotypes due to redundant function (Wyatt et al., 2002).

Currently, the lab is focused on two gravity persistent signal (gps) mutants in Arabidopsis that display an aberrant response to gravity after a cold treatment.  One of these, gps4, displays no gravitropism after a GPS treatment.  Although its molecular identity is known, the exact function of GPS4 remains a mystery.  The gps5 mutant displays enhanced gravitropism in the root, hypocotyl and inflorescence stem after a 90° gravitropic stimulus.  Furthermore, gps5 has drastically increased root and hypocotyl growth.  Currently, research is focused on identifying the molecular target of GPS5, and determining its role in plant growth and development.  This project has been supported by the Summer Research Fellowship and the Undergraduate Research and Creative Activities awards at SIUE.

Biofuels

Another goal of research in the Luesse lab is to increase the production of hydrocarbons by the photosynthetic green algae Botryococcus braunii.  This algae naturally synthesizes and secretes long botryococcenes that can be processed in a similar fashion to crude oil to produce fuel for automobiles or similar devices.  Our goal is to increase the production of these hydrocarbons through environmental and molecular modifications.  We are currently pursuing a reliable transformation protocol that is effective with B.braunii.

Dr. Darron R. Luesse

Office: 3326 Science Lab Building

Lab: 3216 Science Lab Building

Phone: (618)650-2153

email: dluesse@siue.edu

Address:

Box 1651

Southern Illinois University

Edwardsville, IL 62025

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