Physaria fendleri and Ricinus communis LCAT-like phospholipases selectively cleave hydroxy acyl chains from phosphatidylcholine

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  • Producing hydroxy fatty acids (HFAs) in transgenic crops represents a promising strategy to meet our
    demands for specialized plant oils with industrial applications. The expression of Ricinus communis
    (castor) OLEATE 12-HYDROXYLASE (RcFAH12) in Arabidopsis has resulted in only limited
    accumulation of HFA in seeds, which likely results from inefficient transfer of HFAs from their site
    of synthesis (phosphatidylcholine; PC) to triacylglycerol (TAG), especially at the sn-1/3 positions of
    TAG. Phospholipase As (PLAs) may be directly involved in the liberation of HFAs from PC, but the
    functions of their over-expression in HFA accumulation and distribution at TAG in transgenic plants
    have not been well-studied. In this study, the functions of lecithin:cholesterol acyltransferase-like
    PLAs (LCAT-PLAs) in HFA biosynthesis were characterized. LCAT-PLAs were shown to exhibit
    homology to LCAT and mammalian lysosomal PLA2, and to contain a conserved and functional
    Ser/His/Asp catalytic triad. In-vitro assays revealed that LCAT-PLAs from HFA-accumulating plant
    species Physaria fendleri (PfLCAT-PLA) and castor (RcLCAT-PLA) could cleave acyl chains at both
    the sn-1 and sn-2 positions of PC, and displayed substrate selectivity towards sn-2-ricinoleoyl-PC
    over sn-2-oleoyl-PC. Furthermore,co-expression of RcFAH12 with PfLCAT-PLA or RcLCAT-PLA,
    but not Arabidopsis AtLCAT-PLA, resulted in increased HFA occupation at the sn-1/3 positions of
    TAG as well as small but insignificant increases in HFA levels in Arabidopsis seeds compared to
    RcFAH12 expression alone. Therefore, PfLCAT-PLA and RcLCAT-PLA may contribute to HFA
    turnover on PC, and represent potential candidates for engineering unusual fatty acid production in

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    Article (Draft / Submitted)
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    Attribution-NonCommercial 4.0 International
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    • Xu, Y., Caldo, K. M. P., Singer, S. D., Mietkiewska, E., Greer, M. S., Tian, B., ... & Weselake, R. J. (2020). Physaria fendleri and Ricinus communis LCAT‐like phospholipases selectively cleave hydroxy acyl chains from phosphatidylcholine. The Plant Journal.