I have always been fascinated by the complexity of regulatory processes in organisms. It is amazing to see how organisms are able to sense small changes in the environment or in their own metabolism, and to respond by changing the expression of select genes. This can lead to tissue- and/or cell-specific responses such as those involved in protein reallocation and complex formation, or changes in activity spectra of enzymes. The complexity of these events is often increased as many reactions involve multi gene families encoding proteins that have highly similar but not identical sequences that mediate and fine-tune cellular responses.
To study regulatory events in plants we chose as a model system the arogenate dehydratase family (ADTs) in Arabidopsis thaliana. In Arabidopsis there are six members in the ADT family and these enzymes catalyze the last step in the synthesis of phenylalanine. We believe that these enzymes are catalyzing a key step in the production of phenylalanine and thereby co-ordinating the Shikimate pathway and the many branches of phenylpropanoid biosynthesis. We are interested to understand and characterizing as many of the molecular aspects which relate to this gene family inArabidopsisthaliana. The questions we are asking can be at times as simple as: why does Arabidopsisneed six versions of this enzyme? How do these enzymes differ? Are there post-translational modifications? Do these different members of the ADT family contribute to different protein complexes? Are the enzymes or the encoding genes regulated differentially in response to different internal and environmental cues? We already have found some answers. All six ADTs code for proteins which have similar but not identical enzymatic functions. All six ADTs are expressed in all tissues and developmental stages analyzed, but not at the same levels. The encoded proteins have unique subcellular localization patterns. And just to make it even more fun, the six ADTs form homo- and hetero dimers. We still need to investigate if these dimers are formed in all parts of the plant, if they result in unique compositions of protein complexes and what functional consequences these dimer and/or complex formations may have.
Degrees and Institutions
Ph.D. University of Manitoba - Microbiology, 1991
Diploma J.W. Goethe U. Frankfurt, Germany - Biology, 1985
Biology 4562b - Genes and Genomes II
Biology 2581b - Genetics
Saberianfar R, Sattaradeh A, Joensuu JJ, Kohalmi SE, Menassa R 2016. Protein bodies in leaves exchange contents through the endoplasmic reticulum. Frontiers in Plant Sciences 7 http://dx.doi.org/10.3389/fpls.2016.00693 art no 693
Li C, Gu L, Gao L, Chen C, Wei C-Q, Qiu Q, Chien C-W, Wang S, Jiang L, Ai L-F, Chen C-Y, Yang S, Nguyen V, Qi Y, Snyder MP, Burlingame AL, Kohalmi SE, Huang S, Cao X, Wang Z-Y, Wu K, Chen X, Cui Y 2016. Concerted actions of histone H3 lysine 27 demethylase REF6 and chromatin-remodeling ATPase BRM in Arabidopsis. Nature Genetics. 48 687-693.
Li C, Chen C, Gao L, Yang S, Nguyen V, Shi X, Siminovitch K, Kohalmi SE, Huang S, Wu K, Chen X, Cui Y 2015. The Arabidopsis SWI2/SNF2 chromatin remodeler BRAHMA regulates polycomb function during vegetative development and directly activates the flowering repressor gene SVP. PLoS Genetics 11, doi: 10.1371 e1004944.
Gutierrez SP, Saberianfar R, Kohalmi SE, Menassa R 2013. Protein body formation in stable transgenic tobacco expressing elastin-like polypeptide and hydrophobin fusion proteins. BMC Biotechnology, 13, art no 40.
Kaldis A, Ahmad A, Reid A, McGarvey B, Brandle J, Ma S, Jevnikar A, Kohalmi SE, Menassa R 2013. High level production of human interleukin-10 fusions in tobacco suspension cultures. Plant Biotechnology Journal 11, 535-545.
Wang X, Kohalmi SE, Svircev A, Wang A, Sanfaçon H, Tian L 2013. Silencing of host factor eIF(iso)4E gene confers Plum Pox Virus resistance in plum. PLoS ONE 8, art no e50627.
Tian G, Lu Q, Kohalmi SE, Rothstein SJ, Cui Y 2012. Evidence that Arabidopsis Ubiquitin C terminal Hydrolases 1 and 2 associate with the 26S proteasome and the TREX-2 complex. Plant Signaling and Behaviour.
Garrett JJ, Meents MJ, Blackshaw MT, Blackshaw LC, Hou H, Alexander V, Erickson JL, Styranko DM, Kohalmi SE, Schultz EA 2012. A novel semi-dominant allele of MONOPTEROS indicates that negative regulation of auxin response is required for auxin canalization during vein formation. Planta 236, 297-312.
Bross CD, Corea ORA, Kaldis A, Menassa R, Bernards MA, Kohalmi SE 2011. Complementation of the pha2 yeast mutant suggests functional differences for arogenate dehydratases from Arabidopsis thaliana. Plant Physiology and Biochemistry, 49, 882-890.
Brandsma M, Diao H, Wang X, Kohalmi SE, Jevnikar AM, Ma S 2010. Plant-derived recombinant human serum transferrin demonstrates multiple functions. Plant Biotechnology Journal, 8, 489-505.