Functional Characterization of Plant Patatin-like Phospholipase A III in Transgenic Arabidopsis thaliana Producing 18 Carbon Hydroxy Fatty Acids

• Author / Creator

  Lin, Yingyu

• Hydroxy fatty acid (HFA)-enriched oils are valuable in many oleo-chemical industries. The major natural source of HFA, however, is castor (Ricinus communis) seed, which is poisonous to human beings and animals. Although over-expressing a castor OLEATE 12-HYDROXYLASE (RcFAH12) in Arabiodpsis thaliana has been shown to lead to the synthesis of HFAs, a high proportion remained within the membrane phospholipid, phosphatidylcholine. Plant phospholipases A (PLAs) can catalyze the release of fatty acyl chains from the sn-1 and/or sn-2 positions of PC. These free fatty acids are subsequently channeled into the acyl-CoA pool, which provides substrates for TAG synthesis. Thus, it seems that the release of HFA from PC is a critical step for obtaining HFA enriched seed oils. To determine whether the heterologous expression of pPLAIII from HFA-producing plants can enhance the removal of HFA from PC, two pPLAIII genes (pPLAIIIβ and pPLAIIIδ) from castor (Ricinus communis) or Lesquerella fendleri, naturally accumulating >60% of C20-HFA in their seed oils, were expressed in a transgenic line of Arabidopsis producing C18-HFA. In addition, over-expression lines bearing Arabidopsis orthologs, AtpPLAIIIα or AtpPLAIIIδ, respectively, were also generated as controls. Expression of RcpPLAIIIβ resulted in a significant reduction in the HFA content in the seed oil and in PC compared with the control, whereas expressions of other pPLAIII genes did not alter HFA content in the seed oil. These results suggested that pPLAIIIβ may participate in catalyzing the removal of HFA from PC in developing castor seeds. L. fendleri pPLAIII did not appear to participate in the release of C18-HFAs from PC although a possible mechanism of release involving cooperation with elongation of C18 HFA in the acyl-CoA pool could not be ruled out.

• Subjects / Keywords

  • Acyl editing
  • Ricinus communis
  • Lesquerella fendleri
  • Hydroxy fatty acid
  • Arabidopsis-thaliana
  • Patatin-like phospholipase A
  • Castor oil
  • Phosphatidylcholine

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3RR1PS26

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.