Changes in fatty acid composition of Neurospora crassa accompany sexual development and ascospore germination

Fatty acid composition was determined during several stages of sexual development in Neurospora crassa. Triacylglycerol was the predominant acyl lipid in cultures undergoing sexual development. The absolute amounts of triacylglycerol in fertilized cultures varied over time, in contrast to control (unfertilized or mock-fertilized) cultures, in which the amount of triacylglycerol decreased linearly with age. In cultures competent to undergo sexual development, alpha-linoleate was the predominant fatty acid, ranging from 53 to 65% of the total fatty acid mass. alpha-Linolenate was 3% or less of the total fatty acid, in marked contrast to the much higher levels (10-35%) typically reported for vegetative cultures. In fertilized cultures, a slightly higher mass ratio of oleate was also observed. This difference was due to the developing asci: in developing asci and mature ascospores, oleate replaced alpha-linoleate as the predominant fatty acid (45 to 50% of the total). In germinating ascospores, the fatty acid composition approached that of vegetative cultures 6 h after inducing germination by heat activation. These results show that the fatty acid composition of sexual tissues of Neurospora differs substantially from the composition of asexual tissues, and that extensive changes in fatty acid composition correlate with several events in the sexual stage of development.