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First published online May 22, 2003; 10.1104/pp.103.020875 Plant Physiology 132:1249-1259 (2003) © 2003 American Society of Plant Biologists Localization of Nonspecific Lipid Transfer Proteins Correlate with Programmed Cell Death Responses during Endosperm Degradation in Euphorbia lagascae Seedlings1Department of Plant Biology and Forest Genetics, Swedish University of Agricultural Sciences, Box 7080, 750 07 Uppsala, Sweden
When the storage materials have been depleted, the endosperm cells undergo programmed cell death. Very little is known about how the components of the dying cells are recycled and used by the growing seedling. To learn more about endosperm degradation and nutrient recycling, we isolated soluble proteins from the endosperm of Euphorbia lagascae seedlings collected 2, 4, and 6 d after sowing. The protein extracts were subjected to two-dimensional gel electrophoresis. Proteins that increased in amount in the endosperm with time were selected for further analysis with mass spectrometry. We successfully identified 17 proteins, which became more abundant by time during germination. Among these proteins were three E. lagascae lipid transfer proteins (ElLTPs), ElLTP1, ElLTP2, and ElLTP3. Detailed expressional studies were performed on ElLTP1 and ElLTP2. ElLTP1 transcripts were detected in endosperm and cotyledons, whereas ElLTP2 transcripts were only detected in endosperm. Western blots confirmed that ElLTP1 and ElLTP2 accumulate during germination. Immunolocalization experiments showed that ElLTP1 was present in the vessels of the developing cotyledons, and also in the alloplastic space in the endosperm. ElLTP2 formed a concentration gradient in the endosperm, with higher amounts in the inner regions close to the cotyledons, and lesser amounts in the outer regions of the endosperm. On the basis of these data, we propose that ElLTP1 and ElLTP2 are involved in recycling of endosperm lipids, or that they act as protease inhibitors protecting the growing cotyledons from proteases released during programmed cell death.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.020875. 1 This work was supported by the Carl Trygger Foundation, by the Magnus Bergvall Foundation, and by the AgriFunGen Research Program in Functional Genomics at Swedish University of Agricultural Sciences. * Corresponding author; e-mail Johan.Edqvist{at}vbsg.slu.se; fax 46–18–673279. Received January 27, 2003; returned for revision February 28, 2003; accepted March 10, 2003. This article has been cited by other articles:
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