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Research article - Peer-reviewed, 2003

Localization of nonspecific lipid transfer proteins correlate with programmed cell death responses during endosperm degradation in Euphorbia lagascae seedlings

Eklund DM, Edqvist J


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 (EILTPs), EILTP1, EILTP2, and EILTP3. Detailed expressional studies were performed on EILTP1 and EILTP2. EILTP1 transcripts were detected in endosperm and cotyledons, whereas EILTP2 transcripts were only detected in endosperm. Western blots confirmed that ElLTP1 and EILTP2 accumulate during germination. Immunolocalization experiments showed that EILTP1 was present in the vessels of the developing cotyledons, and also in the alloplastic space in the endosperm. EILTP2 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 EILTP1 and EILTP2 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

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Plant Physiology
2003, Volume: 132, number: 3, pages: 1249-1259

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