Similar to humans, plants have an immune system to help defend against parasites and other deleterious infections. The human body is interconnected with cell-to-cell communication to orchestrate an effective immune response. Plant cells are organized in a rigid, static order resembling a brick wall due to their immobility. Plant immunity is very similar to the human innate immune system, which is the first round of defense against infection. Although plants share similar cellular pathways as humans, plants evolved to only have one type of immune response. Specifically, plants do not have adaptive immunity, which establishes immune memory and elicits a stronger immune response in mammals.
Plant cells have markers on their surface to detect infections and other potentially pathogenic invaders. The detected signals from cell sensing markers travel throughout the plant to trigger systemic acquired resistance. Specific immune responses based on infection are launched with specific resistance proteins to fight off pathogens. Plant immunity allows the infection to be contained and avoid infectious spread to the entire plant. The study of plant immunity has implications related to human health. Insights into plant immune biology can provide a better understanding of disease mechanisms and provide potentially new therapeutic targets. Scientists are working to learn more about plant immunology and how they respond to infection.
A recent article in Nature, by Dr. Joseph Ecker and others, demonstrated that plant cells switch biological functions to protect themselves against invading pathogens. Ecker is a Professor and Director of the Genomic Analysis Laboratory at the Salk Institute in California. He is also a Howard Hughes Medical Institute Investigator, which provides funds to conduct groundbreaking research. Ecker’s research focuses on the cellular process that dictates which genes are expressed or not – also referred to as epigenetics. His work has demonstrated the complexity and dynamic versatility of the epigenome as humans age, specifically in brain cells. His work has led to major advances in understanding brain disorders.
Ecker and his team found that when an infection is present, plant cells go into an immune state to respond to disease. The cells become a specialized cell known as Primary Immune Responder (PRIMER) cells. The discovery of PRIMER cells is a major advance to plant biology and further explains the process of plant cell host defense. The PRIMER cell population acts as a source to elicit immunity in cells. Additionally, PRIMER cells were found to be surrounded by ‘bystander’ cells which Ecker and his team conclude relay pathogen detection to the rest of the plant.
The discovery of both cell populations and their role in plant immunity is paradigm shifting and demonstrates how plants actively fight disease. These discoveries have major implications in the field of human health and have the potential to aid in research to combat antimicrobial resistance and climate change. Importantly, the growing threat of antimicrobial resistance leads to escalation of infectious disease. Understanding basic processes of plant immunity can help scientists develop more effective therapies against microorganisms and improve human health.