A new study identifies 111 peroxisomal proteins, including six newly identified ones, in dark-treated plants. It is part of an effort to fully map the functions of plant peroxisomes.
The protein, which helps to construct peroxisomes, also interacts with chloroplasts and mitochondria. The organelles are important for generating and managing plant energy supplies.
Understanding how the plant cell's food processors are built might help us breed better plants and even benefit human medicine.
The Hu lab has deepened our understanding of how cells build up internal parts responsible for producing and breaking down energy, with an eye towards agricultural and medical solutions.
Looking deeper into peroxisome proliferation
The Hu lab has identified a new protein that helps with the division and proliferation of little cellular factories, called peroxisomes. The study is published in the Journal of Integrative Plant Biology.
"Peroxisomes are found in plants and animals, and they perform a variety of functions,” says Dr. Jianping Hu, Professor at the PRL. “They are like food processors that break down fatty acids (fats) into smaller pieces so they can be used by their hosts to produce energy. They also help protect their hosts from environmental stresses."
Over time, researchers have identified a family of proteins that helps these important organelles develop, but they are still trying to understand how they properly divide and proliferate.
“In this study, we specifically identified a protein, called Forkhead-Associated Domain Protein 3 (FHA3), that is found in the cell’s nucleus. We suspected that it plays a role in controlling the genes responsible for dividing the peroxisomes.”
The team found that FHA3 directly represses the expression of a peroxisome division gene, called PEX11b, preventing it from dividing the peroxisome.
In other words, if DNA is like a book, and genes the words, expressing a gene is like speaking the words aloud, bringing their magic to life. FHA3’s work prevents the genes responsible for division from being spoken at the wrong time.
“Indeed, when we identified a mutant plant without FHA3, the level of PEX11b gene expression was higher. We also created a plant with an overabundance of the FHA3 protein, and we found that plant to display deficiencies in peroxisomal division, further suggesting FHA3 is a repressor of peroxisome division.”
A complex web
Hu also found that it is possible that the FHA3 protein interacts with another nuclear protein that controls peroxisome division.
“We previously found that another nuclear protein, HYH, induces peroxisome proliferation by directly promoting the expression of PEX11b. In this study, we discovered that HYH may directly repress the expression of FHA3, thus promoting PEX11b activity indirectly. Therefore, HYH can induce peroxisome proliferation through at least two pathways.”
“Our results lead us to suspect that FHA3 may affect other division factors and physiological processes that remain unknown.”
Research into peroxisomes is particularly of interest in the agricultural and medical fields, as these organelles play a large role in metabolism and defense against diseases.
Future pie-in-the-sky applications could include engineering crops with better metabolism or improved defenses, or cures for devastating human peroxisomal disorders that lead to poor growth, neurological dysfunctions, hearing/visual problems, and liver disease, among other symptoms.
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