University of California, Davis - Plant Immune Sensing Cells in Early Pathogen Invasion

One of the biggest challenges to humans in general is going to be dealing with how we are going to feed the world in a changing climate with an increasing global population.

My name is Gitta Coaker. I’m an Associate Professor at the University of California Davis in the Department of Plant Pathology.

So, my group works on the interaction between bacterial pathogens and plants. And we work with a variety of different plants. At the controlled environmental facility here at UC Davis, we primarily work on the model plant, Arabidopsis Thaliana. We also work with Nicotiana benthamiana, and we also work with tomato. And what we’re really interested in my lab is to gain a mechanistic understanding of how the plant can use its innate or pre-formed immune system to recognize bacterial pathogens.

Numerous genetic screens were conducted in the 90s, in early 2000s and they’ve identified a clear set of genes that are really important for immunity. But, what’s thought now is to identify the existing genes, there may be some functional redundancy at play, etcetera. And so a lot of the proteins and genes that we work with may have some subtle phenotypes, and so there it’s really important to be able to have precise control, to be able to accurately measure phenotypes, and be able to do that over multiple replications in many different plants to have appropriate statistics.

So we found that actually the majority of immune receptors in plants, whether they’re – have extra cellular domains, or whether they’re primarily present inside plant cells. They’re expressed at the RNA and protein level in guard cells.

We’ve also found that the components that they monitor in important key signaling proteins downstream are also present in guard cells, so those appear to actually truly be effective immune-sensing cells.

What we’ve done now is we’ve made tissue-specific promoters where we’re only expressing an immune receptor in guard cells, only in epidermal cells, and only in mesophyll cells, and preliminary results from that indicate that guard cells are active immune-sensing cells, they can dynamically respond, and they’re responsible for limiting early pathogen invasion.

We know that plants can be attacked by all classes of pathogens, and that can cause significant yield losses and even decimate certain crops depending on the environmental conditions. And we know that climate change is going to result in more severe weather patterns, so we need to have a better understanding of how the plant recognizes different pathogens; how it can respond to those pathogens.

Truly, if we can understand the genetics and also the biochemistry and cell biological changes that occur, then we can engineer either through genetic engineering or through traditional breeding crops that can more effectively resist pathogens in the field.