Changes in lipid composition during somatic embryogenesis in leaves of Cichorium

The present studies were conducted to investigate the changes in lipid and fatty acid composition during the earliest stages of somatic embryogenesis in leaf tissues of the Cichorium hybrid '474'. The presence of glycerol in the culture medium during the induction step allowed to separate two phases in the embryogenic process. Firstly, cells are induced for morphogenetic competence (induction phase) and secondly, they express an embryogenic competence (expression phase). The analysis of fatty acid composition of total lipids showed that the percentage of linolenic acid (18:3) decreased while that of linoleic acid (18:2) increased throughout the culture period. A comparison with a non-embryogenic genotype of Cichorium indicated a higher increase of linoleate content in embryogenic genotype. The incorporation of [C-14] glycerol into lipid classes was studied in leaf tissues. During the induction step, label was confined almost exclusively in polar lipids, particularly in phosphatidylcholine (PC). An important increase of labeled triacylglycerols (TAG) amounts was noted during the expression step. The accumulation of 18:2 was observed in PC and also in TAG. These results show that the early stages of somatic embryogenesis are associated with the increase of PC and TAG which are mainly enriched in 18:2. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.