The Role of a Histone Methyltransferase in Arabidopsis Pathogen Defense

Date of Award

August 2017

Degree Type


Degree Name

Master of Science (MS)




Ramesh Raina

Subject Categories

Life Sciences


The continuous increase in human population and effects of climate change as time passes have made us dependent on more durable and sustainable resources and food products. However, with these massive changes, we cannot continue to produce our crops at the same rate due to limited arable agricultural land. Hence, there is a great need for crops resistant to a variety of pathogens, which will increase as the temperatures around the world change. Epigenetic regulators play an important role in controlling gene expression. These genes regulate chromatin remodeling in response to environmental cues such as temperature, biotic and abiotic stresses such as pathogens, salinity and drought. Currently, not many genes are known to play a role in both epigenetics and pathogen defense. In this work, I identify a type of epigenetic regulator called histone methyltransferases, SET DOMAIN GROUP1 (SDG1) and SDG25, which are required for defense against the bacterial pathogen Pseudomonas syringae. Another lab has since published the characterization of SDG25. Here, the characterization of the role of SDG1, a gene identified twenty years ago, in pathogen defense is presented. Plants with a mutation in this gene have a multitude of phenotypes: early flowering, altered leaf shape, susceptibility to bacterial and fungal pathogens, early senescence, late onset of hypersensitive response (HR) in response to avirulent bacterial pathogens, and resistance to oxidative stress. Surprisingly, the mutants do not have a significant difference in terms of gene expression of known defense related genes suggesting that SDG1 does not regulate these genes. These results suggest a model where SDG1 controls the defense mechanism of Arabidopsis in an unknown pathway that is separate from the known salicylic acid (SA) and jasmonic acid (JA) pathways.


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