Research
Our research is focused on understanding the genetics controlling disease resistance and the defense response in maize.
Diverse populations of maize often display extreme variation for disease resistance. We would like to understand the genetics and physiology that controls this variation.
The picture on the right shows how we score variation for symptoms caused by the disease southern leaf blight in a population of maize.
Disease symptoms might vary between lines for a number of reasons.
Plants have ways of detecting the general features of microbes and eliciting defense responses. We have shown that different maize (and sorghum) lines vary for this general response, called Pattern-Triggered Immunity (PTI).
The picture on the left shows variation in the maize PTI response among 25 diverse lines and is from the publication:
Zhang, Vet al (2017). Genetic dissection of the maize (Zea mays L.) MAMP response. Theoretical and Applied Genetics. 130: 1155. doi:10.1007/s00122-017-2876-6
Plants also have genes that recognize features of specific pathogens and which provide strong and very specific resistance against these particular pathogens. This type of response is termed Effector-Triggered Immunity (ETI). A component of the ETI response is the Hypersensitive response (HR), which is a rapid cell death at the point of pathogen penetration. We have used genetic techniques to amplify HR and show that it also varies between maize lines.
Directly below we show variation in HR among maize lines- see Olukolu, et al. (2014) A Genome-Wide Association Study of the Maize Hypersensitive Defense Response Identifies Genes That Cluster in Related Pathways. PLoS Genetics DOI: 10.1371/journal.pgen.1004562
Below that is a picture of a genetic chimera showing strong HR in the lower area of the leaf and a sharp border with no response in the upper area- which indicates that HR is cell-autonomous. For more details see Karre, et al. (2021) Maize Plants Chimeric for an Autoactive Resistance Gene Display a Cell Autonomous Hypersensitive Response but Non-Cell Autonomous Defense Signaling. Mol. Plant-Microbe Interact., https://doi.org/10.1094/MPMI-04-20-0091-R
In other cases variation in disease resistance is caused by variation in genes associated with biochemical pathways that produce chemicals required for suppressing pathogen growth. We identified a gene that was associated with resistance to multiple diseases and with the production of the structural polymer lignin
See Yang et al (2017) A gene encoding maize caffeoyl-CoA O-methyltransferase confers quantitative resistance to multiple pathogens. Nature Genetics 49:1364–1372 doi:10.1038/ng.3919
The picture to the right shows lignin stained in a susceptible (left) and resistant (right) leaf
Using a combination of molecular biology, plant pathology, quantitative genetics and field research we have mapped and identified a number of other genes controlling variation in disease resistance and the defense response.
We are particularly interested in the connection between variation in disease resistance and the defense response and in genes that confer resistance to multiple diseases.
Picture on the left shows the correlations between resistance to three foliar maize diseases ( Southern leaf blight-SLB, Grey Leaf SPot-GLS, and Northern Leaf Blight-NLB) among a set of 300 diverse lines. See- Wisser, et al. (2011) : Multivariate analysis of maize disease resistances suggests a pleiotropic genetic basis and implicates a GST gene. PNAS 108:7339-7344
We are also interested in the effects of disease resistance on yield and on interactions with beneficial microbes.
The best way to find out about our current interests is to look at our publications on google scholar or to email me at pjbalint@ncsu.edu.