Glenn Hicks, R
IIGB Academic Administrator
Mailing Address:Botany and Plant Sciences
Keen Hall /2023
University of California
Riverside, CA 92521
Phone: (951) 827-3707
Fax: (951) 827-2155
Degree(s):PhD 1991 Oregon State University
BS 1981 University of California, Davis
College/Division Affiliation:College of Natural and Agricultural Sciences
Center/Inst Affiliation(s):Center for Plant Cell Biology
Areas Of Expertise:Cell Biology; Chemical Genomics; Plant Biology; Endomembrane Trafficking; Plant Biotechnology
Awards / Honors:
NASA Graduate Student Research Program Fellowship
NSF Postdoctoral Fellowship in Plant Biology
In addition to Academic Administrator of IIGB, I am actively engaged in research aimed at understanding basic endomembrane processes in collaboration with Dr. Natasha Raikhel's laboratory.
Endocytosis and Protein Recycling
I am interested in taking several broad approaches to understand endomembrane trafficking. In particular, I have been focused on dissecting processes involved in endocytosis and plasma membrane/endosome recycling which are poorly understood yet essential processes. Pollen is an attractive system for such studies in that it displays growth that is strongly tip focused, and as a single cell, the endomembranes and their organization can be viewed by microscopy. We have combined this with a relatively new approach of chemcial genomics in which drug-like chemicals are used to perturb and understand biological processes. We have developed a screen for chemicals that affect protein secretion in pollen. Among the resulting compounds, we have looked for those that effect protein recycling to and from the plasma membrane of Arabidopsis seedlings. The goal of this research is to understand cargo sorting at endosomes using novel chemical reagents and to uncover new genes through target identification.
a) Discover novel chemicals that affect secretion in pollen. We have expressed several pollen tube tip plasma membrane and secreted fluorescent protein markers into transgenic tobacco and scored for anomalous targeting to the plasma membrane which depends upon a functional secretory apparatus. We have developed a screen in pollen using a 384-well format and automated microscopy permitting the rapid screening of thousands of chemicals. The approach has worked remarkably well, and several chemicals appear to produce novel effects in the recycling of plasma membrane proteins in pollen as well as Arabidopsisi seedlings.
b) Dissect protein recycling and endosomal sorting. Recently, we have focused on a chemical endosidin 1 (ES1) which affects the recycling of the auxin transporters PIN2 and AUX1 in Arabidopsis specifically without affecting the transporters PIN1 and PIN7. In fact, ES1causes the affected proteins to agglomerate into endomembrane bodies (endosidin bodies) which are defined by several endosome markers. An important conclusion is that PIN2 and AUX1 utilize distinct recycling pathways compared to PIN1 and PIN7. More exciting, ES1 affects the recycling of the brassinosteroid receptor BRI1 and blocks the expression of a brassinosteroid reporter gene. Beyond blocking BRI1 signaling, ES1 also phenocopies a bri1 loss-of-function mutant. Our results indicate that PIN2, AUX1 and BRI1 are within a population of endosomes that are sorted from endosomes containing PIN1/7. Hence, we have begun to define distinct pathways of endosome sorting that might be difficult to distinguish genetically.
Sortin1 Target Identification
Sortins are compounds that lead to increased secretion of vacuolar proteins in yeast. Several of these compounds called Sortin1 and Sortin2 were found to lead to aberrant vacuoles and increased secretion of vacuolar proteins in Arabidopsis. To identify the pathways affected by Sortin1, we identified a set of mutants hypersensitive to Sortin1. We have mapped one of the mutants genetically based on defects in vacuole morphology and a mutation within a transcription factor has been found. we are currently investigating the significance of this factor in endomembrane trafficking.