A morte celular ocorre do mesmo modo em plantas e animais

quinta-feira, outubro 22, 2009

Cell Death Occurs In Same Way In Plants And Animals

ScienceDaily (Oct. 21, 2009) — Research has previously assumed that animals and plants developed different genetic programs for cell death. Now an international collaboration of research teams, including one at the Swedish University of Agricultural Sciences, has shown that parts of the genetic programs that determine programmed cell death in plants and animals are actually evolutionarily related and moreover function in a similar way.

The findings were published in Nature Cell Biology October 11.
For plants and animals, and for humans as well, it is important that cells both can develop and die under controlled forms. The process where cells die under such forms is called programmed cell death. Disruptions of this process can lead to various diseases such as cancer, when too few cells die, or neurological disorders such as Parkinson's, when too many cell die.

In both plant and animal cells that undergo programmed cell death, the protein TUDOR-SN is broken down. In pollen, from the model plant mouse-ear cress, a reduction in TUDOR-SN leads to fragmentation of DNA (red signal) and premature cell death. (Credit: Photo by Andrei P. Smertenko)

The findings are published jointly by research teams at SLU (Swedish University of Agricultural Sciences) and the Karolinska Institute, the universities of Durham (UK), Tampere (Finland), and Malaga (Spain) under the direction of Peter Bozhkov, who works at SLU in Uppsala, Sweden. The scientists have performed comparative studies of an evolutionarily conserved protein called TUDOR-SN in cell lines from mice and humans and in the plants norway spruce and mouse-ear cress. In both plant and animal cells that undergo programmed cell death, TUDOR-SN is degraded by specific proteins, so-called proteases.

The proteases in animal cells belong to a family of proteins called caspases, which are enzymes. Plants do not have caspases – instead TUDOR-SN is broken down by so-called meta-caspases, which are assumed to be ancestral to the caspases found in animal cells. For the first time, these scientists have been able to demonstrate that a protein, TUDOR-SN, is degraded by similar proteases in both plant and animal cells and that the cleavage of TUDOR-SN abrogate its pro-survival function. The scientists have thereby discovered a further connection between the plant and animal kingdoms. The results now in print will therefore play a major role in future studies of this important protein family.

Cells that lack TUDOR-SN often experience premature programmed cell death. Furthermore, functional studies at the organism level in the model plant mouse-ear cress show that TUDOR-SN is necessary for the development of embryos and pollen. The researchers interpret the results to mean that TUDOR-SN is important in preventing programmed cell death from being activated in cells that are to remain alive.

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Journal reference:

Jens F. Sundström, Alena Vaculova, Andrei P. Smertenko, Eugene I. Savenkov, Anna Golovko, Elena Minina, Budhi S. Tiwari, Salvador Rodriguez-Nieto, Andrey A. Zamyatnin, Jr, Tuuli Välineva, Juha Saarikettu, Mikko J. Frilander, Maria F. Suarez, Anton Zavialov, Ulf Ståhl, Patrick J. Hussey, Olli Silvennoinen, Eva Sundberg, Boris Zhivotovsky & Peter V. Bozhkov. Tudor staphylococcal nuclease is an evolutionarily conserved component of the programmed cell death degradome. Nature Cell Biology, 2009; DOI: 10.1038/ncb1979

Nature Cell Biology
Published online: 11 October 2009 | doi:10.1038/ncb1979

Tudor staphylococcal nuclease is an evolutionarily conserved component of the programmed cell death degradome

Jens F. Sundström1,9, Alena Vaculova2,9, Andrei P. Smertenko3,9, Eugene I. Savenkov1,9, Anna Golovko1,9, Elena Minina1,9, Budhi S. Tiwari1, Salvador Rodriguez-Nieto2, Andrey A. Zamyatnin, Jr1, Tuuli Välineva4, Juha Saarikettu4, Mikko J. Frilander5, Maria F. Suarez6, Anton Zavialov7, Ulf Ståhl1, Patrick J. Hussey3, Olli Silvennoinen4,8, Eva Sundberg1, Boris Zhivotovsky2 & Peter V. Bozhkov1

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Programmed cell death (PCD) is executed by proteases, which cleave diverse proteins thus modulating their biochemical and cellular functions. Proteases of the caspase family and hundreds of caspase substrates constitute a major part of the PCD degradome in animals1, 2. Plants lack close homologues of caspases, but instead possess an ancestral family of cysteine proteases, metacaspases3, 4. Although metacaspases are essential for PCD5, 6, 7, their natural substrates remain unknown4, 8. Here we show that metacaspase mcII-Pa cleaves a phylogenetically conserved protein, TSN (Tudor staphylococcal nuclease), during both developmental and stress-induced PCD. TSN knockdown leads to activation of ectopic cell death during reproduction, impairing plant fertility. Surprisingly, human TSN (also known as p100 or SND1), a multifunctional regulator of gene expression9, 10, 11, 12, 13, 14, 15, is cleaved by caspase-3 during apoptosis. This cleavage impairs the ability of TSN to activate mRNA splicing, inhibits its ribonuclease activity and is important for the execution of apoptosis. Our results establish TSN as the first biological substrate of metacaspase and demonstrate that despite the divergence of plants and animals from a common ancestor about one billion years ago and their use of distinct PCD pathways, both have retained a common mechanism to compromise cell viability through the cleavage of the same substrate, TSN.

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Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences, Box 7080, SE-75007 Uppsala, Sweden.
Institute of Environmental Medicine, Karolinska Institutet, Box 210, SE-17177, Stockholm, Sweden.
The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK.
Institute of Medical Technology, University of Tampere, FIN-33014 Tampere, Finland.
Institute of Biotechnology, University of Helsinki, FIN-00014 Helsinki, Finland.
Departamento de Biologia Molecular y Bioquimica, Facultad de Ciencias, Universidad de Malaga, Campus de Teatinos, 29071 Malaga, Spain.
Department of Molecular Biology, Biomedical Center, Swedish University of Agricultural Sciences, Box 590, SE-75124 Uppsala, Sweden.
Department of Clinical Microbiology, Tampere University Hospital, FIN-33520 Tampere, Finland.

These authors contributed equally to this work.

Correspondence to: Peter V. Bozhkov1 e-mail: peter.bozhkov@vbsg.slu.se

Correspondence to: Andrei P. Smertenko3,9 e-mail: andrei.smertenko@durham.ac.uk