PHOSPHATIDYLSERINE SYNTHASE1 is required for microspore development in Arabidopsis thaliana

Abstract

SUMMARYPhosphatidylserine (PS) has many important biological roles, but little is known about its role in plants, partly because of its low abundance. We show here that PS is enriched in Arabidopsis floral tissues and that genetic disruption of PS biosynthesis decreased heterozygote fertility due to inhibition of pollen maturation. At1g15110, designated PSS1, encodes a base-exchange-type PS synthase. Escherichia coli cells expressing PSS1 accumulated PS in the presence of L-serine at 23°C. Promoter-GUS assays showed PSS1 expression in developing anther pollen and tapetum. A few seeds with pss1-1 and pss1-2 knockout alleles escaped embryonic lethality but developed into sterile dwarf mutant plants. These plants contained no PS, verifying that PSS1 is essential for PS biosynthesis. Reciprocal crossing revealed reduced pss1 transmission via male gametophytes, predicting a rate of 61.6% pss1-1 pollen defects in PSS1/pss1-1 plants. Alexander's staining of inseparable qrt1-1 PSS1/pss1-1 quartets revealed a rate of 42% having three or four dead pollen grains, suggesting sporophytic pss1-1 cell death effects. Analysis with the nuclear stain 4¢,6-diamidino-2-phenylindole (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. However, among unicellular microspores from PSS1/pss1-2 GFP-LactC2 plants, all anucleate microspores showed little GFP-LactC2 fluorescence, suggesting that pss1-2 microspores are more sensitive to sporophytic defects or show partial gametophytic defects.

The Phosphorylated Pathway of Serine Biosynthesis Is Essential Both for Male Gametophyte and Embryo Development and for Root Growth in Arabidopsis

“…Michard et al (2011) showed that D-Ser is involved in a plant signaling mechanism between male gametophyte and pistil, affecting pollen tube growth and morphogenesis. Yamaoka et al (2011) showed that mutants of phosphatidylserine synthase (PSS1), an enzyme involved in phosphatidylserine biosynthesis, exhibit similar phenotypes as psp1.1/psp1.1 mutants, that is, diminished fertility due to inhibition of pollen maturation and to a high embryo abortion rate. However, we discovered differences between the mutants.…”

“…The role of Ser and/or Ser derivatives in plant reproduction has been recently demonstrated (Michard et al, 2011;Yamaoka et al, 2011). Michard et al (2011) showed that D-Ser is involved in a plant signaling mechanism between male gametophyte and pistil, affecting pollen tube growth and morphogenesis.…”

Role of Aminoalcoholphosphotransferases 1 and 2 in Phospholipid Homeostasis in Arabidopsis

“…On the other hand, we observed an increase in PE species with long-chain fatty acids in AAPT KO/RNAi lines, and PS contains a higher percentage of long-chain FAs than other species. In addition, one PS synthase (PSS1) was found in the Arabidopsis genome, which is of base-exchange type and uses PE and serine as substrates (Yamaoka et al, 2011). The small increase of PE with long-chained fatty acids could mean that some PS is converted to PE via the CDP-DAG pathway and/or the baseexchange pathway (Figure 12).…”

ArabidopsisPhosphoglycerate Dehydrogenase1 of the Phosphoserine Pathway Is Essential for Development and Required for Ammonium Assimilation and Tryptophan Biosynthesis

“…PHOSPHATIDYLSERINE SYNTHASE1 led to embryo lethality and affected microspore development (Yamaoka et al, 2011). The lack of Ser normally synthesized via the PS pathway might result in reduced phosphatidylserine synthesis and lead to the abortion of embryos homozygous for pgdh1 or psp mutations.…”