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  • Functional analysis of phos...
    Pejchar, Přemysl; Sekereš, Juraj; Novotný, Ondřej; Žárský, Viktor; Potocký, Martin

    The Plant journal : for cell and molecular biology, July 2020, 2020-07-00, 20200701, Letnik: 103, Številka: 1
    Journal Article

    Summary Phosphatidic acid (PA), an important signalling and metabolic phospholipid, is predominantly localized in the subapical plasma membrane (PM) of growing pollen tubes. PA can be produced from structural phospholipids by phospholipase D (PLD), but the isoforms responsible for production of PM PA were not identified yet and their functional roles remain unknown. Following genome‐wide bioinformatic analysis of the PLD family in tobacco, we focused on the pollen‐overrepresented PLDδ class. Combining live‐cell imaging, gene overexpression, lipid‐binding and structural bioinformatics, we characterized five NtPLDδ isoforms. Distinct PLDδ isoforms preferentially localize to the cytoplasm or subapical PM. Using fluorescence recovery after photobleaching, domain deletion and swapping analyses we show that membrane‐bound PLDδs are tightly bound to PM, primarily via the central catalytic domain. Overexpression analyses suggested isoform PLDδ3 as the most important member of the PLDδ subfamily active in pollen tubes. Moreover, only PLDδ3 shows significant constitutive PLD activity in vivo and, in turn, PA promotes binding of PLDδ3 to the PM. This forms a positive feedback loop leading to PA accumulation and the formation of massive PM invaginations. Tightly controlled production of PA generated by PLDδ3 at the PM is important for maintaining the balance between various membrane trafficking processes that are crucial for plant cell tip growth. Significance Statement Phosphatidic acid has been demonstrated as an important molecule defining the identity of plasma membrane, but its production from structural phospholipids by phospholipase D is still not completely understood. This study describes a comprehensive bioinformatic, localization and functional analysis of phospholipase Dδ subfamily in tobacco pollen tubes, showing that distinct isoforms have different membrane targeting mechanisms, dynamics, in vivo activity and the effect on cell membrane traffic.