Abstract
Phosphatidylserine (PS) is a very minor lipid (1.7%) in photosynthetic tissues of in A. thaliana. However, it is relatively enriched in roots and flowers, comprising ~5.9% and ~20.6% of extraplastidial membrane phospholipids, respectively. Arabidopsis contains a base-exchange-type PS synthase (AtPSS1) that synthesizes PS from phosphatidylethanolamine (PE) and serine. AtPSS1 is relatively highly expressed in the ER and nuclear membranes of root and anther cells. atpss1 mutation causes partial inhibition of pollen development, suggesting that PS biosynthesis is required for normal pollen development.
To evaluate the physiological functions of PS in anther, we herein constructed the PS biosensor LactC2-eGFP that is a fusion protein between eGFP and the C2 domain of lactadherin (Yeung et al., 2008). LactC2-eGFP was localized in the nuclear membranes of tetrads. However, it was localized in mitochondria in microspores. These results suggest that translocalization of PS from the nuclear membranes to mitochondria could play an important in pollen development.
