Ken Ko - Professor

Research: My research is focused on plant rhomboid proteins. Rhomboid proteins modulate many important cellular processes such as protein transport, development, stress adaptation and cancer.  The most complex and least understood group of rhomboid proteins (rhomboids) is found in plants.  In Arabidopsis, there are at least 13 different rhomboid-encoding genes at work in any given individual plant.  Arabidopsis rhomboids can be divided into 4 different sub-groups - 2 for proteolytically “active” forms and 2 for proteolytically “inactive” forms that function through interactions only.  The various rhomboids function in different parts of the plant cell, from the cell surface to the internal membranes of plastids and mitochondria.  In the plastids alone, there are at least 4 forms in play, both active and inactive types.  There are also other forms that arise from alternative splicing, leading to a very complex network of rhomboids in the plastids.  The purpose of the plastid rhomboid network remains a mystery.  Some of the early observations point to roles for plastid rhomboids in development, growth productivity and stress adaptation.

Our current research plan is to characterize all rhomboid forms that function in the plastids of Arabidopsis, a popular model organism for plant researchers.  We are also investigating the recently-discovered links between plastid rhomboids and processes like cell cycle, tissue development and stress adaptation.

Some Recent Publications: 

• Sedivy-Haley, K., Powles, J., Ko, K. 2012. Characterization of two alternative splice variants associated with the Arabidopsis rhomboid protein gene At1g25290.  Botany.  In press.
• Sedivy-Haley, K,, Powles, J., Newcomb, W., Ko, K.  2011. Molecular characterization of organellar rhomboid proteins in Arabidopsis.  Botany 89: 873-885.
• Powles, J., Savage, P., Wu ,E., Karakasis, K., Ko, K. 2011. Motif-based evidence that a plastid translocon component acts like a rhomboid protease substrate in yeast mitochondria. Botany 89: 499-511.
• Karakasis, K., Taylor, D., Ko, K. 2007. Uncovering a link between a plastid translocon component and rhomboid proteases using yeast mitochondria-based assays.  Plant and Cell Physiology 48: 655-661.
• Ko, K., Chan, K., Karakasis, K., Pedram, B. 2006. Plastid protein transport: Coping with diversity. Canadian Journal of Botany 84: 543-550. 
• Ko, K., Taylor, D., Argenton, P., Innes, J., Pedram, B., Siebert, F., Granell, A., Ko, Z. 2005. Evidence that the plastid translocon Tic40 components possess modulating capabilities. Journal of Biological Chemistry 280: 215-224.