Alex C Schultink
I grew up in the state of Michigan and moved to Calfiornia to attend Stanford University. At Stanford I majored in Biology and did a minor Computer Science. After graduating from Stanford 2009 I began a PhD program studying Plant Biology at UC Berkeley. I joined the lab of Markus Pauly and studied plant cell wall biosynthesis. I worked mostly with the plant Arabidopsis thaliana to uncover new genes invovled in the bisynthesis of the cell wall polysaccharide xyloglcuan. After finishing my PhD in 2013 I changed fields slightly to study plant microbe interactions as a post doc in the lab of Brian Staskawicz.
I'm currently a postdoc in teh lab of Brian Staskawicz at UC Berkeley. I'm interested in the identification of new plant disease resistance genes / pathways and uncovering the mechanism for how they work. My current projects are focused on bacterial pathogens from the genus Xanthomonas. There are many species of Xanthomonas that can infect different crop species including tomato, pepper, rice, cassava, citrus, lettuce, and walnut. There are currently few effective options for control of this pathogen and it can cause significant productivity losses, particularly in humid weather conditions. Bacterial pathogens such as Xanthomonas are able to secrete effector proteins into plant cells. The typical Xanthomonas pathogen has approximately 30 effector proteins which act to suppress the immune response of the plant or manipulate the metabolism of the host for the benefit of the pathogen. Plants have a large gene family of immune receptors, known as NLR receptors, which are able to directly or indirectly detect the presence of effector proteins. Activation of these NLR receptors typically leads to a strong immune which causes localized cell death for the plant and restricts pathogen proliferation. A plant that contains an NLR receptor capable of recognizing an effector protein from an invading pathogen is typically completely resistant to that pathogen. If one knows the effector repertoire of a pathogen and the corresponding NLR receptors to recognize one or more of those effectors, one can engineer a crop species with the appropriate NLR receptors to confer resistance. Unfortunately, there is no known cognate NLR receptor for the vast majority of pathogen effector proteins. Additionally, while some NLR receptors are functional across plant species, many are dependent on other proteins either for recognition of the effector protein or for activation of downstream immune responses. Additionally, if a single NLR receptor is used to confer resistance against a pathogen in a crop species, the pathogen can often overcome this resistance by acquiring mutations in the recognized effector gene or completely losing the gene. My work in the Staskawicz lab is focused on identifying new genes and pathways that are able to recognize effector proteins from various species of Xanthomonas to overcome these limitations to allow for improved methods of genetic control of plant pathogens.
I'm using Nicotiana benthamiana as a platform for forward and reverse genetics approaches for the identification of disease resistance pathways. N. benthamiana is able to recognize several effector proteins from Xanthomonas, either when delivered by the pathogen or when expressed transiently using Agrobacterium. I screened an EMS population of N. benthamiana and identified seven mutants defective for the recognition of one or more of these effector proteins. I've identified the causative mutations for two of the mutants so far and am working on the remaining five. In parallel, I conducted a reverse genetic screen using Viral Induced Gene Silencing (VIGS) to identify the NLR dependencies for several effector proteins. I'm continuing to identify additional genes involved in these recognition pathways and am also working to understand the biochemical mechanisms involved.
For my PhD work I studied cell wall biosynthesis in the lab of Markus Pauly at UC Berkeley. We used forward genetics, reverse genetics and comparative genomics to identify several new genes involved in the biosynthesis of the cell wall polysaccharide xyloglucan. Using expression profiling of developing nasturtium seeds, which accumulate large amounts of xyloglucan as a seed storage polysaccharide, we identified a previously unstudied candidate xyloglucan glycosyltransferase gene. We demonstrated the function of the orthologous Arabidopsis gene which is required for the addition of galactose to the polysaccharide at a particular position. While Arabidopsis plants contain no arabinosylated xyloglucan, this sugar is found in xyloglucan of tomato plants and several other clades. By using a comparative genomics approach, I found gene candidates and subsequently demonstrated the activity of two xyloglucan arabinosyltransferase genes, named XST1 and XST2, from tomato. Using a forward genetic approach for Arabidopsis mutants with altered xyloglucan structures, we identified a protein involved in the pathway of polysaccharide acetylation. The protein, named AXY9, localizes to the Golgi lumen and may be part of a shuttle system to provide polysaccharide acetyltransferases with activated acetyl groups.
USDA NIFA Postdoctoral Fellowship Awardee, April 2016
Life Science Research Foundation Postdoctoral Scholar Fellowship Finalist, Feb 2016
PMB Department Retreat Poster Prize Honorable Mention, Sept 2013
PMB Department Retreat Poster Prize 2nd Place, Sept 2012
NSF Graduate Research Fellowship Program Honorable Mention, March 2010
NIH Pre-doctoral Genetics Training Grant, August 2009 – July 2012
Daniel Arnon Graduate Student Fellowship, August 2009 – July 2010
Lauren D. Weinstein Award for undergraduate teaching, Stanford, June 2009
VPUE Grant for undergraduate research, Stanford, Summer 2007
Biology 44Y 1st Place Poster, 2nd Place Presentation, Stanford, June 2007
National Youth Science Camp Delegate for State of Michigan, Summer 2005