Greg Martin
Greg Martin has retired from the Boyce Thompson Institute, and the Martin lab is closed.
Research Overview
How do bacteria infect plants, and how do plants defend themselves from such attacks?
The long-term goal of research in the Martin laboratory was to use knowledge gained about the molecular basis of plant-pathogen interactions to develop plants with increased natural resistance to diseases. Such plants would require fewer applications of pesticides, producing economic and environmental benefits while providing food for consumers with less pesticide residue.
The Martin laboratory studied the molecular basis of bacterial infection processes and the plant immune system. The research focused on speck disease, which is caused by the infection of tomato leaves with the bacterial pathogen Pseudomonas syringae pv. tomato. This is an economically important disease that can decrease both the yield and quality of tomato fruits. It also serves as an excellent experimental system for studying the molecular mechanisms that underlie plant-pathogen interactions and how they have evolved. Many experimental resources, including an increasing number of genome sequences, are available for both tomato and P. s. pv. tomato. Work relied on diverse experimental approaches involving methods derived from the fields of biochemistry, bioinformatics, cell biology, forward and reverse genetics, genomics, molecular biology, plant breeding, plant pathology, and structural biology.
In the interaction of Pseudomonas with tomato, the plant responds rapidly to a potential infection by detecting certain conserved molecules expressed by the pathogen. At this stage, the pathogen uses a specialized secretion system to deliver virulence proteins, such as AvrPto and AvrPtoB, into the plant cell. These pathogen proteins suppress early host defenses and thereby promote disease susceptibility. Some tomato varieties express a resistance gene, Pto, which encodes a protein that detects the presence of AvrPto or AvrPtoB and activates a second strong immune system that halts the progression of bacterial speck disease.
The Martin lab studied many aspects of the molecular mechanisms that underlie the bacterial infection process and the plant response to infection. One project takes advantage of the genetic natural variation present in wild relatives of tomato to identify new genes that contribute to plant immunity. These genes provide insights into the plant immune system and can also be bred into new tomato varieties to enhance disease resistance. A second project relied on next-generation sequencing methods to identify tomato genes whose expression increases during the interaction with P. s. pv. tomato. The expression of these genes is then reduced by using virus-induced gene silencing, or the genes are mutated using CRISPR/Cas9, to test whether they make a demonstrable contribution to immunity.