Identification of two phosphatidylinositol/phosphatidylcholine transfer protein genes that are predominately transcribed in the flowers of Arabidopsis thaliana.

The Sec14 protein (Sec14p) and its homologs are involved in the transfer of phosphatidylinositol/phosphatidylcholine phospholipids in eukaryotic cells. In the completely sequenced genome of Arabidopsis thaliana, multiple genes encoding putative Sec14p homologs have been predicted based on bioinformatic analysis. Here we report the identification of two yeast Sec14-like genes (designated as AtSFH3 and AtSFH12, respectively) that are predominately transcribed in Arabidopsis flowers. The deduced amino acid sequences of AtSfh3p and AtSfh12p exhibited high similarity to that of Sec14p. Ectopic expression of AtSfh3p or AtSfh12p corrected the high temperature sensitive phenotype caused by Sec14p functional deficiency in Saccharomyces cerevisiae, indicating that the two plant homologs are functional in the intracellular environment. AtSFH3 transcripts were detected in flowers, stems and immature siliques but not roots and leaves, with a relatively higher transcript level in the flowers. In contrast, AtSFH12 transcripts were only detectable in the flowers. Based on histochemical staining of beta-glucuronidase (GUS) activities in the transgenic Arabidopsis plants harboring promoter::GUS constructs, AtSFH3 transcription was first detected in the stigma papillae of the flowers at stage 11, and then in the pollen grains before and after fertilization. On the other hand, AtSFH12 transcription was only found in the mature and germinating pollen grains. The information from this study may provide useful clue for further analysis of the function of plant Sec14p homologs in the development of the male gametic cells and/or the fertilization process in higher plants.

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