Abstract
Although lipids are rich in reproductive organ in plant, physiological roles of each lipid species have not yet well understood. We have studied the role of sterols on the development of reproductive organs by reverse-genetic strategy using Arabidopsis.
HMG-CoA reductase, the key enzyme of sterol biosynthesis, is encoded by HMG1 and HMG2 in the Arabidopsis genome. hmg1 shows dwarfing, early senescence and male sterility, and hmg1 hmg2 were male gametphyte lethal. Microscopic analyses showed pollen-coat was absent in hmg1 and hmg1 hmg2 microspores were stunted.
Next, we focused the steroidal backbone synthetic step. Oxidosqualene is cyclized to cycloartenol by CAS1 and lanosterol by LAS1. The knockout allele of CAS1, cas1-2, was male gametophyte lethal. However, the microspores of cas1-2 were less damaged than those of hmg1 hmg2. These results suggest that metabolites from mevalonate to oxidosqualene and/or sterol biosynthetic pathway via lanosterol are important for the development of microspores.
