Abstract
Phosphatidylserine (PS) has many important biological roles, but little is known in plants. At1g15110, designated PSS1, encodes a base-exchange-type PS synthase. Reciprocal crossing revealed reduced pss1 transmission via male gametophytes, predicting a rate of 61.6% pss1-1 pollen death in PSS1/pss1-1 plants. However, Alexander's staining indicated 79.9% dead pss1-1 pollen, suggesting that pss1-1 and PSS1 pollen must undergo sporophytic cell death. Analysis with the nuclear stain DAPI showed that all tetrads from PSS1/pss1-1 anthers retain their nuclei, whereas unicellular microspores were sometimes anucleate. Transgenic Arabidopsis expressing a GFP-LactC2 construct that binds PS revealed vesicular staining in tetrads and bicellular microspores and nuclear membrane staining in unicellular microspores. Hence, distribution and/or transport of PS across membranes were dynamically regulated in pollen microspores, and nuclear localization of PS seems to be important for maturation of Arabidopsis microspores.
