Scientists at North Carolina State University have discovered a phenomenon never seen before in plants while studying molecular changes inside tree cells as wood is formed.
In research published online in Proceedings of the National Academy of Sciences the week of Aug. 20, the team found that one member of a family of proteins called transcription factors took control of a cascade of genes involved in forming wood, which includes a substance called lignin that binds fibers together and gives wood its strength.
The controller protein regulated gene expression on multiple levels, preventing abnormal or stunted plant growth. And it did so in a novel way.
The controller, a spliced variant of the SND1 family, was found in the cytoplasm outside the cell nucleus. This is abnormal, because transcription factor proteins are always in the nucleus. But when one of the four other proteins in its family group was present, the spliced variant was carried into the nucleus, where it bound to the family member, creating a new type of molecule that suppressed the expression of a cascade of genes.
“This is nothing that’s been observed before in plants,” says Dr. Vincent Chiang, co-director of NC State’s Forest Biotechnology Group with Dr. Ron Sederoff. Chiang’s research team was the first to produce a transgenic tree with reduced lignin. High lignin levels are desirable for lumber, but lignin is removed during the process of making paper or manufacturing biofuels.
Chiang, a professor in the College of Natural Resources, described the team’s finding as the long-sought path to understanding the hierarchy of gene regulation for wood formation.
Lead authors are Dr. Quanzi Li, senior research associate, who discovered the controller protein, and doctoral student Ying-Chung Lin, who carried out extensive experimental work, demonstrating with Li that the controller protein was carried into the nucleus.
The research was funded with a grant from the U.S. Department of Energy’s Office of Biological and Environmental Research.
Splice variant of the SND1 transcription factor is a dominant negative of SND1 members and their regulation in Populus trichocarpa. Quanzi Li, Ying-Chung Lin, Ying-Hsuan Sun, Jian Song, Hao Chen, Xing-Hai Zhang, Ronald R. Sederoff, and Vincent L. Chiang. Proceedings of the National Academy of Sciences, Aug. 20, 2012. doi:10.1073/pnas.1212977109
North Carolina State University