Research - Institute of Plant Biology - Laboratory of Functional Cell Biology

Attila FEHÉR
Head, Principal Investigator

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Mónika DOMOKI Staff Scientist
Dalma MÉNESI Staff Scientist
Judit BÍRÓ Staff Scientist
Gyöngyvér KATONA Technician
Róza NAGY Technician

FUNCTIONAL CELL BIOLOGY

Plants exhibit a remarkable developmental plasticity as a consequence of their sessile way of life. During plant ontogenesis, exogenous (environmental) and endogenous (developmental) signals converge on interlinked signaling pathways having dynamic impacts on plant form and function. We use molecular, biochemical and cellular approaches to reveal and characterize plant-specific pathways of cellular signaling that underlie this developmental plasticity.


Signaling through ROP GTPases

RHO GTPases constitute a major branch of the Ras superfamily of small GTP-binding proteins and function as GDP/GTP switches that are activated by diverse extracellular stimuli. Once activated, each RHO GTPase interacts with a wide spectrum of functionally diverse downstream effectors to initiate signaling pathways. In plants, a specific class of RHO GTPases exists forming the ROP subfamily. Their involvement in various cellular processes (e.g. cell elongation, tip growth, pathogen defence, hormone signaling etc.) has been demonstrated, but the signaling cascades they are involved in are hardly explored. It is more and more obvious, however, that plants have evolved specific RHO (ROP) GTPase effectors as compared to other eukaryotes. Especially their links to upstream receptor and downstream effector kinases seem to be unique and largely unknown.

In our laboratory we identified a specific group of plant kinases exhibiting GTP-bound ROP GTPase-dependent in vitro activity. These kinases can be considered therefore the first potential ROP GTPase effector kinases in plants. Our aim is to identify further elements of this signaling pathway and to verify its biological significance using transgenic and mutant plants. Moreover, the structure of the plant ROP-interacting kinases (RRKs) predicts a novel, specific way for their functional interaction with ROP GTPases, as they do not have any GTPase-binding motif. Therefore we also aim to reveal the structural and biochemical background of this molecular interaction. Furthermore, we are interested in the characterization of the link of upstream receptor kinases to ROP GTPase signaling. In this field we collaborate with the group of Dr. Antje Berken (Max Planck Institute of Molecular Physiology, Dortmund).




Figure 1. Potential ways for the regulation of ROP GTPase activity by phosphorylation. The three indicated pathways are still hypothetical as supported only by in direct or in vitro data. Further regulatory steps based on the phosphorylation of ROP regulators and effectors can also be hypothesized but are presently unknown. Red arrows indicate activation, blue arrows inhibition/inactivation, violet arrows both. ROP – „Rho of plants” GTPase; GEF – guanine nucleotide exchange factor; GAP – GTPaseactivating protein; GDI – guanine nucleotide dissociation inhibitor;




Figure 2. In vitro activation of the Medicago RRK1 kinase by the constitutive active (CA) Rop6 GTPase. (For details: Dorjgotov et al. (2009) FEBS Letters 583:1175)


Nucleosome assembly-related proteins (NRPs) and plant development

Nucleosome assembly proteins (NAPs) and their close relatives, the NAP-related proteins (NRPs) are multifunctional proteins having roles, in addition to nucleosome assembly, in gene transcription, cell division, apoptosis and in various signaling pathways. We demonstrated that Arabidopsis NRPs have in vitro and in vivo histone phosphatase inhibitor activity and that this activity may be associated with the improved heat shock survival of NRP-overexpressing transgenic Arabidopsis plants. We also identified NRP-containing protein complexes associated with cell cycle and transcriptional regulation. Furthermore, it was also established, in collaboration with CropDesign NV, Ghent, Belgium, that NRP-overexpressing rice plants gain a considerable yield increase. Our further aim is to identify the components of the NRP-related protein complexes and to define their biological functions in association with plant development and stress tolerance.




Figure 3. Comparison of the gene exprerssion pattern of young seeds from drought (D) or drought and heat (DH) treated Capelle Desprez (CA) and Plainsman V (PL) wheat cultivars using a custome microarray. (blue decreased, red increased relative expression)



Genomic approaches to reveal gene expression networks associated with plant developmental and stress tolerance pathways

We use microarray technology, EST sequencing and real-time quantitative PCR (RT-QPCR) to identify gene expression patterns associated with plant-specific developmental pathways such as somatic embryogenesis, fertilization and seed development. Related to these studies, a custom oligonucleotide microarray representing 15,000 wheat genes related to seed-development has been set up based on previous in silico gene expression analysis. The microarray was successfully used to identify the effect of drought and heat on early seed development. This work is in collaboration with Dr. Beáta Barnabás (Agricultural Research Institute, HAS, Martonvásár, Hungary).


Selected publications

Pasternak, T. P., Prinsen, E., Ayaydin, F., Potters, G., Asard, H., Onckelen, H. A. and Fehér, A. (2002). The role of auxin, pH, and stress in the activation of embryogenic cell division in leaf protoplast-derived cells of alfalfa. Plant Physiology 129: 1807-1819.

Fehér, A., Pasternak, T.P. and Dudits, D. (2003). Transition of somatic plant cells to an embryogenic state. Plant Cell, Tissue, and Organ Culture 74:201-228.

Ötvös, K., Pasternak, T. P., Miskolczi, P., Domoki, M., Dorjgotov, D., Szűcs, A., Bottka, S., Dudits, D. and Fehér, A. (2005). Nitric oxide is required for, and promotes auxin-mediated activation of, cell division and embryogenic cell formation but does not influence cell cycle progression in alfalfa cell cultures. The Plant Journal 43: 849-860.

Domoki, M., Györgyey, J., Biro, J., Pasternak, T.P., Zvara, A., Bottka, S., Puskás., L.G., Dudits, D. and Fehér, A. (2006). Identification and characterization of genes associated with the induction of embryogenic competence in leaf-protoplast-derived alfalfa cells. BBA-Gene Structure and Expression 1759: 543-551.

Zhiponova, M.K., Pettkó-Szandtner, A., Stelkovics, É., Neer, Z., Bottka, S., Krenács, T., Dudits, D., Fehér, A. and Szilák, L. (2006). Mitosis-specific promoter of the alfalfa cyclin-dependent kinase gene (Medsa;CDKB2;1) is activated by wounding and ethylene in a non-cell division-dependent manner. Plant Physiology 140: 693-703.

Szűcs, A., Dorjgotov, D., Ötvös, K., Fodor, C., Domoki, M., Györgyey, J., Kaló, P., Kiss, G.B., Dudits, D. and Fehér, A. (2006). Characterization of three Rop GTPase genes of alfalfa (Medicago sativa L.). BBA Gene Structure and Expression 1759: 108-115.

Fehér, A. (2006). Why somatic plant cells start to form embryos? In: A. Mujib and J. Samaj eds., Somatic Embryogenesis, Plant Cell Monographs, Vol. 2., Springer-Verlag, Berlin Heidelberg, pp. 85-101.

Pasternak, T., Ötvös, K., Domoki, M. and Fehér, A. (2007). Linked activation of cell division and oxidative stress defense in alfalfa leaf protoplast-derived cells is dependent on exogenous auxin. Plant Growth Regulation 51: 109-117.

Fehér, A., Ötvös, K., Pasternak, T. and Pettkó-Szandtner, A. (2008). The involvement of reactive oxygen species (ROS) in the cell cycle activation (G0-to-G1 transition) of plant cells. Plant Signaling & Behavior 3: 823-826.

Fehér, A., Jurca, M.E., Fodor-Dunai, C. and Dorjgotov, D. (2008). Regulation of ROP GTPase signaling at the gene expression level. The Open Plant Science Journal 2: 21-30.

Barnabás, B., Jäger, K. and Fehér, A. (2008). The effect of drought and heat stress on reproductive processes in cereals. Plant, Cell & Environment 31: 11-38.

Jurca, M.E., Bottka, S. and Fehér, A. (2008). Characterization of a family of Arabidopsis receptor-like cytoplasmic kinases (RLCK class VI). Plant Cell Reports 27: 739-748.

Dorjgotov, D., Jurca, M.E., Fodor-Dunai, C., Szűcs, A., Ötvös, K., Klement, É., Bíró, J. and Fehér, A. (2009). Plant Rho-Type (Rop) GTPase-Dependent activation of receptor-like cytoplasmic kinases in vitro. FEBS Letters 583: 1175-1182.