Hydroxy fatty acid synthesis and lipid gene expression during seed development in Lesquerella fendleri

Lesquerella fendleri is a developing oilseed crop in the U.S. The seed oil of L. fendleri is rich in lesquerolic acid (14-hydroxy-eicos-cis-11-enoic acid: 20:1OH), a hydroxy fatty acid (HFA) with potential uses in industrial materials. Although the synthesis pathway of HFA is extensively studied, the regulatory mechanism underlying synthesis and accumulation of 20:1OH is largely unknown. In this study, we investigated the fatty acid composition and lipid gene expression pattern in developing seeds of L. fendleri, from 7 days after pollination (DAP) to desiccation (49 DAP). The results showed that accumulation of 20:1OH started at 21 DAP, increased quickly between 21 and 35 DAP and reached a plateau, about 50–55% of total lipids, at 35–49 DAP. In addition, two other HFAs, ricinoleic (12-hydroxy-octadec-cis-9-enoic acid: 18:1OH) and auricolic (14-hydroxy-eicos-cis-11,17-enoic acid: 20:2OH) acids were present at low levels during various stages of seed development. Ricinoleic acid could be detected as early as 14 DAP whereas 20:2OH began to accumulate at 21 DAP or later. Using real-time polymerase chain reaction, we quantified the transcript level of three lipid genes, LFAH12 (bifunctional oleate 12-hydroxylase:desaturase), LfKCS3 (3-ketoacyl-CoA synthase) and LfFen1 (oleate 12-desaturase). While all of these genes displayed a bell-shaped expression pattern with a peak at 35 DAP and a sharp decline at 42–49 DAP, they had different expression levels during early seed development and maximum inductions. Based on the defined time course of seed development, the relationship between gene expression and HFA accumulation is discussed.