Programmed cell death during the transition from multicellular structures to globular embryos in barley androgenesis |
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Authors: | Email author" target="_blank">Simone?de?F?MaraschinEmail author Gwéna?l?Gaussand Amada?Pulido Adela?Olmedilla Gerda?E?M?Lamers Henrie?Korthout Herman?P?Spaink Mei?Wang |
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Institution: | (1) Center for Phytotechnology LU/TNO, Leiden University, Wassenaarseweg 64, 2333 AL Leiden, The Netherlands;(2) Departamento de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain;(3) TNO Department of Applied Plant Sciences, Zernikedreef 9, P.O. Box 2215, 2301 CE Leiden, The Netherlands;(4) Institute of Biology Leiden, Leiden University, Wassenaarseweg 64, P.O. Box 9505, 2300 RA Leiden, The Netherlands |
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Abstract: | Androgenesis represents one of the most fascinating examples of cell differentiation in plants. In barley, the conversion of stressed uninucleate microspores into embryo-like structures is highly efficient. One of the bottlenecks in this process is the successful release of embryo-like structures out of the exine wall of microspores. In the present work, morphological and biochemical studies were performed during the transition from multicellular structures to globular embryos. Exine wall rupture and subsequent globular embryo formation were observed only in microspores that divided asymmetrically. Independent divisions of the generative and the vegetative nuclei gave rise to heterogeneous multicellular structures, which were composed of two different cellular domains: small cells with condensed chromatin structure and large cells with normal chromatin structure. During exine wall rupture, the small cells died and their death marked the site of exine wall rupture. Cell death in the small cell domain showed typical features of plant programmed cell death. Chromatin condensation and DNA degradation preceded cell detachment and cytoplasm dismantling, a process that was characterized by the formation of vesicles and vacuoles that contained cytoplasmic material. This morphotype of programmed cell death was accompanied by an increase in the activity of caspase-3-like proteases. The orchestration of such a death program culminated in the elimination of the small generative domain, and further embryogenesis was carried out by the large vegetative domain. To date, this is the first report to show evidence that programmed cell death takes part in the development of microspore-derived embryos. |
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Keywords: | Androgenesis Barley Caspase-3 like proteases Exine wall Programmed cell death TUNEL |
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