All species of plants, wild and cultivated alike, are subject to disease — a fact that can be devastating to an economy, wildlife and humans.
|Biology Assistant Professor Karolina Mukhtar, right, and biology graduate student Lucas Boatwright study the possibilities of providing adequate, sustainable food resources and disease-resistant crops using genetic engineering.|
Plant diseases lead to reduced crop yields, decreased nutritional value and sometimes contaminated food and feed with toxic compounds. The result is millions of dollars in annual economic losses in the United States and tens of billions in losses worldwide.
But genetically modifying crop plants to be disease-resistant by adding one extra gene could yield plants that are better equipped to fight stressors and diseases, especially bacterial ones.
Karolina Mukhtar, Ph.D., assistant professor of biology, says it could be possible.
“And it could save millions of dollars that are lost every year in the United States because of pests and pathogens,” she says. “Even more in Third World countries. Today’s global population of nearly 7 billion is expected to jump to 10 billion by 2050, and 1 billion people worldwide already are suffering from malnutrition.
“Engineering plants to create a better product under stress conditions is the way to feed the world and ease the burden on poor, underdeveloped nations.”
Mukhtar, who came to the biology department in fall 2010, is UAB’s only plant researcher studying the possibilities of providing adequate, sustainable food resources and disease-resistant crops using genetic engineering. Her lab does not develop new crop varieties; rather, she focuses her genetic research on Arabidopsis thaliana, a small plant in the mustard family. Its genome was sequenced 11 years ago.
“In our laboratory, we are using cutting-edge technologies, like microarrays, proteomics, next-generation sequencing and robotic-assisted screens,” she says. “We also use systems-level and genomic approaches to answer important questions in plant immunity.”
That research has proved the important role that analysis of plant genomes can play in understanding basic principles of biology — both its direct application in agriculture and also relevance to humans, she says.
“There is a need for substantial basic research in labs like mine using Arabidopsis,” Muhktar says. “We have all the genetic tools we need. We can make transgenics. We can make mutants. We have collections of molecular tools and markers. The availability of molecular tools for Arabidopsis is equivalent to any animal model. Once you know what gene causes certain trait in Arabidopsis, you can go to any other plant you want and you’ll be able to find an equivalent gene in that plant. Instead of looking for a needle in a haystack, you already know where to look.”
To understand the molecular basis of disease resistance in plants, Mukhtar’s lab studies two major groups of plant pathogens —biotrophs and necrotrophs.
One of her projects is the transcriptional and post-transcriptional regulation of plant immunity and cellular stresses. Endoplasmic reticulum stress (also known as Unfolded Protein Response or UPR) is a ubiquitous mechanism observed in all eukaryotic organisms from yeast to humans to plants that fine-tunes the folding capacity of the endoplasmic reticulum proteins during stress.
“Our laboratory is a pioneer in unraveling at least two out of three major branches of plant UPR in connection with pathogen and biotic stresses such as bacterial infection,” Mukhtar says.
In Mukhtar’s previous work at Duke University, she identified a transcription factor that acts as a master molecular switch for activation of pathogen-induced endoplasmic reticulum-centered defense response.
“Basically, we have master switches in the cells that can turn genes on or off,” Mukhtar says. “If you can find a master switch like that, you can control hundreds of genes at the same time. I identified one of those master switches earlier. Now, we’re trying to find nodes that control small players beneath the master switch, so when it’s off, those genes stay down.”
By knowing these few key regulatory genes needed to create broad-spectrum resistance, the potential is there to genetically modify a crop plant by putting one extra gene in to it.
“That could give it a great many options,” Mukhtar says. “With different pathogens, it will be able to fight off stressors better in the field. It will help with diseases, mostly bacterial diseases.”
Resistance to necrotrophic pathogens
Mukhtar also studies necrotrophic fungal pathogens, which affect many agronomically important plant species including grapes and berries and cruciferous crops such as canola. These pathogens cause millions of dollars in losses in the United States each year.
These fungal pathogens actively kill host tissue prior to colonization, usually through the secretion of a cocktail of mycotoxins.
“We are generating mutants that are either insensitive or hypersensitive to one of the major toxins and correlate this phenotype with disease resistance,” Muhktar says. “Hundreds of mutants are in the pipeline and at least in one case we can demonstrate that mutant that is insensitive to toxin is also fully resistant to this deadly pathogen.”
Muhktar says this is the first example where a morphologically normal Arabidopsis mutant is resistant to this deadly necrotrophic pathogen.
“We are very confident that we will have a great resource of novel, resistant mutants,” she says. “Obtaining this information can be extrapolated to the crop plants in order to breed more resistant varieties.”