Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2006
Publication Date: 12/28/2005
Citation: Chen, M., Han, G., Dietrich, C.R., Dunn, T.M., Cahoon, E.B. 2005. The essential nature of sphingolipids in plants as revealed by the identification and functional characterization of the arabidopsis LCB1 subunit of serine palmitoyltransferase. The Plant Cell. 18:3576-3593. Interpretive Summary: The lipid composition of the membranes of plant cells plays an important role in the ability of crops to respond to and mitigate environmental stresses such as drought and frost. In the reported studies, a gene for a key enzyme in the formation of sphingolipids was identified in plants. Sphingolipids are major structural components of the plasma membrane or outer membrane of plant cells and may play a role in regulating the plant’s response to environmental stimuli. This research demonstrated that sphingolipids are essential in plants and reduced biosynthesis of these lipids has profound effects on the growth and development of plants. This research provides useful information for biologists and plant breeders who study drought and freeze tolerance in crop plants such as soybean. It is anticipated that this research will contribute to the development of crops for US farmers that are more resistant to environmental extremes.
Technical Abstract: Serine palmitoyltransferase (SPT) catalyzes the first step of sphingolipid biosynthesis. In yeast and mammalian cells, SPT is a heterodimer that consists of LCB1 and LCB2 subunits, which together form the active site of this enzyme. By contrast, the subunit composition of SPT has not been fully demonstrated in plants. Lacking in our understanding of the plant SPT is the functional identification of the LCB1 subunit. Here we show that the predicted gene for the Arabidopsis LCB1 (AtLCB1; At4g36480) encodes a genuine subunit of SPT that is able to complement the sphingolipid long-chain base auxotrophy of Saccharomyces cerevisiae SPT mutants when co-expressed with the Arabidopsis LCB2 (AtLCB2). In addition, homozygous T-DNA mutants for the AtLCB1 gene were not recoverable, and analyses of heterozygous T-DNA lines indicated that the loss of viability results from embryo lethality. Furthermore, partial RNAi suppression of AtLCB1 expression was accompanied by a marked reduction in plant size that resulted primarily from reduced cell expansion. Interestingly, sphingolipid content on a weight basis was not significantly changed in the RNAi suppression plants, suggesting that plants compensate for down-regulation of sphingolipid synthesis by reduced growth. AtLCB1-RNAi suppression plants also displayed altered leaf morphology and a three- to four-fold increase in the relative content of the sphingolipid long-chain base phytosphingosine. Overall, functional characterization of AtLCB1 revealed that sphingolipids are essential components of plant cells and contribute to the growth and development of plants.