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K-State Today

October 26, 2023

Larry Griffing to present Division of Biology Seminar

Submitted by Division of Biology

Larry Griffing, associate professor and director of the Microscopy and Imaging Center in the department of biology at Texas A&M University, will present "Potential Functions of ER-Plasma Membrane Contact Sites in Plants: Sterol Transport and Regulation of Near-UV Light Signal Transduction and Division in Chloroplasts," as part of the Division of Biology Seminar Series at 3:30 p.m. Monday, Oct. 30, in 221 Ackert Hall.

The organelles of eukaryotic cells associate with each other directly through contact. However, the function of interorganellar contacts in plants has yet to be discovered. Candidates for the function of contact sites between the endoplasmic reticulum and the plasma membrane in other model systems  — yeast and animal cells — include sterol transport and cytosolic calcium entry. Our evidence supports the model that endoplasmic reticulum-plasma membrane contact sites play a role in retrograde traffic of sterols from the plasma membrane into elongating cells of plant roots, but with the new finding that the major target for sterol uptake is the nuclear envelope, a subdomain of the endoplasmic reticulum.

The need for a retrograde transport mechanism is based on a model for organismal sterol transport through the phloem from the plant apex to the elongating root cells. With efficient uptake of the sterols, we also found that a negative-feedback loop regulates sterol metabolism in young seedlings. The association of the endoplasmic reticulum with the plasma membrane is also important in tethering chloroplasts to the outer epidermal plasma membrane in the growing hypocotyl of young seedlings. Brief, near-UV photostimulation of the junction between the chloroplast and the endoplasmic reticulum when the chloroplast is tethered to the plasma membrane produces a transient calcium wave in the plant cell. This is not a wound response, but part of a calcium signal regulating cytoskeleton dynamics and organellar clustering. Griffing's lab is currently exploring photoreceptor candidates and the possibility that endoplasmic reticulum contact sites help regulate chloroplast division.

If you would like to visit with Griffing, please contact Kathrin Schrick at kschrick@k-state.edu