Speaker: Sharon A. Kessler, associate professor in the Department of Botany and Plant Pathology at Purdue University

Title: "Processing extracellular information: MLO signaling from roots to flowers"

Abstract: MILDEW RESISTANCE-O (MLO) proteins are key signaling molecules during plant cell responses to their external environments.  MLO proteins were originally discovered as powdery mildew susceptibility factors and have since been implicated in several processes throughout plant growth and development.  In this seminar, I will discuss recent advances towards understanding the function of MLO proteins in pollen tube reception and in root hair tip growth, two cases where a highly polarized cell communicates with its external environment to achieve a specific outcome.  During pollen tube reception, intercellular communication between the pollen tube and the synergid cells of the female gametophyte leads to subcellular events in both cell types culminating in the rupture of the tip-growing pollen tube and release of the sperm cells to achieve double fertilization. Pollen tube arrival at the ovule triggers FERONIA receptor kinase signaling and leads to the trafficking of the NORTIA (NTA) MLO protein from the Golgi to the filiform apparatus. At the filiform apparatus, NTA acts as a calcium channel to promote calcium oscillations in the synergids that are necessary to ensure pollen tube rupture to release the sperm cells at the correct time and place. Thus, Golgi retention and selective protein trafficking in the synergids act to appropriately scale the intercellular communication between the male and female gametophytes. In root hairs, FERONIA also triggers in MLO-mediated responses that promote root hair tip growth. Similarities and differences in these FER/MLO signal transduction cascades will be discussed. 

Host: Michelle Guo, genetics, development and cell biology assistant professor