Corn Spots Know the Meaning of Self-Sacrifice

Corn spots, it seems, know the meaning of self-sacrifice. When under attack from a pathogen, these plants commit "cell suicide" to prevent any further damage, a new study describes, and scientists are just beginning to understand how this defense mechanism works.

During this cell suicide, corn plants kill their own cells near the site of attack to thwart the attacker's efforts. This cell sacrifice can cause very small, often microscopic, spots or lesions on the plant.

Researchers from North Carolina (NC) State University who wanted to learn more about this "spotty" defense identified a number of candidate genes and cellular processes that control this so-called hypersensitive defense response (HR) in corn. The findings, published in the journal PLOS Genetics, could lead to better defense responses in corn and other plants like trees.

NC researchers, in collaboration with a team from Purdue University, examined more than 3,300 maize plants that contained a similar mutation - that is, they all had exaggerated HR because one particular resistance gene, Rp1-D21, doesn't turn off.

"It's similar to a human having an auto-immune response that never stops," corresponding author Dr. Peter Balint-Kurti said in a statement. "This mutation causes a corn plant to inappropriately trigger this hypersensitive defense response, causing spots on the corn plant as well as stunted growth."

After sifting through some 26.5 million points in the two to three billion base pair genome, the researchers found 44 candidate genes that appear to be involved in defense response, programmed cell death, cell wall modification and a few other responses linked to the self-sacrificing behavior.

"All of the processes associated with the top candidate genes have been previously associated with HR," Balint-Kurti added. "Hopefully this work provides an opening to really characterize this important defense response and learn more about it in other plants."