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Physaria fendleri and Ricinus communis lecithin:cholesterol acyltransferase‐like phospholipases selectively cleave hydroxy acyl chains from phosphatidylcholine
Author(s) -
Xu Yang,
Caldo Kristian Mark P.,
Singer Stacy D.,
Mietkiewska Elzbieta,
Greer Michael S.,
Tian Bo,
Dyer John M.,
Smith Mark,
Zhou XueRong,
Qiu Xiao,
Weselake Randall J.,
Chen Guanqun
Publication year - 2021
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.15050
Subject(s) - phosphatidylcholine , arabidopsis , acyltransferase , biochemistry , ricinus , catalytic triad , phospholipase , transgene , lecithin , biology , arabidopsis thaliana , chemistry , phospholipid , mutant , gene , enzyme , active site , membrane
SUMMARY Production of 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 HFAs in seeds, which probably 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 work, the functions of lecithin:cholesterol acyltransferase‐like PLAs (LCAT‐PLAs) in HFA biosynthesis were characterized. The LCAT‐PLAs were shown to exhibit homology to LCAT and mammalian lysosomal PLA 2 , and to contain a conserved and functional Ser/His/Asp catalytic triad. In vitro assays revealed that LCAT‐PLAs from the 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 occupation of HFA at the sn ‐1/3 positions of TAG as well as small but insignificant increases in HFA levels in Arabidopsis seeds compared with RcFAH12 expression alone. Therefore, PfLCAT‐PLA and RcLCAT‐PLA may contribute to HFA turnover on PC, and represent potential candidates for engineering the production of unusual fatty acids in crops.