Department of Plant Biology

Plant endomembranes at the MSU-DOE Plant Research Lab

Dynamics of Secretory Membrane Traffic in Plant Cells

Plants are major players in the biotechnology boom for production of a wide range of compounds. If we are to make best use of plants as living factories, we must understand the mechanics of the production process.

Plants are dynamic systems—they virtually hum with activity at the molecular level. Each cell is a tiny factory, building materials according to instructions provided by DNA. Using genetic means, plants can be coaxed into producing valuable compounds. These are built and packaged in a series of dynamic cell compartments, comparable to an assembly line in a factory. These compartments, collectively named the secretory pathway, are essential to the life of a cell.

Organelles that make up the secretory pathway are in a constant state of exchanging molecules, such as proteins, lipids, and sugars. Secretory proteins are synthesized in the endoplasmic reticulum (ER), then transported forward to a processing compartment, the Golgi apparatus, to be distributed to the plasma membrane or the vacuole. Forward traffic of macromolecules is counterbalanced by retrograde transport between organelles to allow homeostasis of membrane and resident proteins. Despite intense communication, secretory organelles maintain their morphological and functional identity. How they achieve this is mostly unknown.

The research in our laboratory focuses on the investigation of how secretory molecules are packaged and which mechanisms regulate the shipment of compounds to the final destination. We also explore the mechanisms that lead to the establishment and maintenance of organelles of the secretory pathway. The analysis of these topics will give clues to key biological questions on the plant secretory pathway and will provide a better understanding of mechanisms that govern the steps of secretion in plants to enable us to regulate cell secretion and to acquire genetic tools that may lead to better management of natural resources.

Our understanding of the plant secretory pathway has often been hampered by the lack of adequate investigative techniques. In our laboratory we employ fluorescent protein technology combined with advanced imaging technology to investigate dynamics of the plant secretory pathway. These new investigative imaging techniques allow us to watch the secretory pathway in living plant cells in real time.

 Figure 1. Confocal image of a tobacco leaf epidermal cell co-expressing a fluorescent Golgi marker (pseudocolored red) and a fluorescent marker that labels the actin cytoskeleton (pseudo­colored green).