Abstract
Phosphatidylserine (PS) is a minor phospholipid in plant cells, representing <2% of total lipids. In flowers, however, its content amounts to 10% of total lipids, suggestive of its uncharacterized function. PS is synthesized via a CDP-diacylglycerol pathway in Escherichia coli and yeast, whereas it is synthesized via a base-exchange pathway from phosphatidylcholine or phosphatidylethanolamine in mammals. Arabidopsis thaliana has a putative PS synthase gene for the base-exchange pathway (PSS1; At1g15110), whose gene product remains to be described. To understandPSS1 function in plants, especially in flowers, we herein characterized a T-DNA insertion mutant, designated pss1-1. Homozygous pss1-1 caused recessive embryonic lethality at the four-cell stage. Heterozygotic plants produced abnormal male gametophytes, representing 40% of pss1-1 gametophytes. Transgenic Arabidopsis expressing a PSS1-Enhanced Yellow Fluorescence Protein (EYFP) fusion showed reticular fluorescent images within pollen, suggesting that PSS1 plays an important role in male gametogenesis in A. thaliana.
