Encyclopedia of Lipidomics

Living Edition
| Editors: Markus R. Wenk

Monoacylglycerol (MAG) in Plants: Functional Diversity of

  • Ellen HornungEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-94-007-7864-1_138-1

Keywords

Neutral Lipid Glycerol Backbone Ionization Tandem Mass Spectrometry Electrospray Ionization Tandem Mass Spectrometry Saturated Acyl 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Synonyms

Definitions

Suberin

lipophilic polymer found in specialized cell to insulate cells or tissue from surrounding cells

Structure and Occurrence

Monoacylglycerols (MAGs) are neutral lipids. They are comprised of one fatty acid (FA) connected to a glycerol backbone via ester bond (Fig. 1). The fatty acid can be either in sn1−/sn-3 or sn2-position, also referred to as α-MAG or β-MAG, respectively.
Fig. 1

Monoacylglyerol with one acyl chain (R) at sn1-position

The composition of MAG is quite diverse depending on their occurrence. Like other neutral lipids, MAG can be found in the seed oil, but only in minor amounts (Hirayama and Hujii 1965; Panekina et al. 1978). MAG is also detected in developing seeds. In maturing soybean seeds, MAG comprised the major neutral lipid 20 days after flowering although the amount decreased rapidly in further developmental stages (Hirayama and Hujii 1965). MAGs are also a substantial part of surface wax of leaves and fruits, and here preferentially an ω-hydroxy acid is esterified to the glycerol backbone (Graça et al. 2002; Simpson and Ohlrogge 2016). MAGs are also a part of suberin and were detected, for example, in suberin of cork, containing α,ω-dicarbolic acids (Graça and Santos 2006) as well as in suberin of root wax in Arabidopsis thaliana, where the esterified component was identified as saturated acyl chains of C22 – C30 (Li et al. 2007).

Biosynthesis

MAG can be synthesized in different ways. One possibility is the degradation of di- and triacylglycerol (DAG and TAG) by lipases to MAG (Perry and Harwood 1993). In a second pathway (Fig. 2) lysophosphatidic acid (LPA) is dephosphorylated by LPA phosphatase to MAG (Shekar et al. 2002; Reddy et al. 2010). MAG can also be produced by specific acyl-CoA/glycerol-3-phosphate (G3P) acyltransferases (GPAT) that are bifunctional (Li et al. 2007). These GPAT transfer acyl-CoAs preferentially to the sn2-position of G3P (Fig. 2), and a phosphatase domain produces MAG instead of LPA (Yang et al. 2010).
Fig. 2

Biosynthesis pathways of monoacylglyerol in plants (Adapted and modified from Reddy et al. 2010)

Functions

MAG functions predominantly as the precursor in the TAG biosynthesis via different pathways. It was shown that in developing peanut cotyledons (Tumaney et al. 2001, Parthibane et al. 2012), DAG is produced from MAG by acyl-CoA/monoacylglycerol acyltransferase (MGAT), similar to DAG synthesis in mammalians. MAG also takes part in transacylating reactions producing DAG or lysophosphatidylcholine in developing seeds (Stobart et al. 1997) or in surface wax of fruits (Simpson and Ohlrogge 2016). Besides the function in TAG biosynthesis, MAG also plays a role in cutin biosynthesis (Petit et al. 2016). It was suggested that sn2-MAG or β-MAG is acting as precursor in cutin and surface wax assembly, as it can be exported by epidermal cells (Yang et al. 2010; Simpson and Ohlrogge 2016).

Detection of MAG in Plant Lipid Extracts

MAGs may be analyzed in similar way to other neutral lipids via thin-layer chromatography (TLC), followed by gas chromatography (GC) to determine their fatty acid composition. Additionally MAG can be analyzed in lipidomic studies via electrospray ionization tandem mass spectrometry (ESI-MS).

Cross-References

References

  1. Graça J, Schreiber L, Rodrigues J, Pereira H. Glycerol and glyceryl esters of ω-hydroxyacids in cutins. Phytochemistry. 2002;61:205–15.CrossRefPubMedGoogle Scholar
  2. Graça J, Santos S. Glycerol-derived ester oligomers from cork suberin. Chem Phys Lipids. 2006;144:96–107.CrossRefPubMedGoogle Scholar
  3. Hirayama O, Hujii K. Glyceride structure and biosynthesis of natural fats part III. Biosynthetic process of tryglycerides in maturing soybean seed. Agr Biol Chem. 1965;29:1–6.Google Scholar
  4. Li Y, Beisson F, Ohlrogge J, Pollard M. Monoacylglycerols are components of root waxes and can be produced in the aerial cuticle by ectopic expression of a suberin-associated acyltransferase. Plant Physiol. 2007;144:1267–77.CrossRefPubMedPubMedCentralGoogle Scholar
  5. Panekina TV, Gusakova SD, Tabak MY, Umarov AU. Neutral lipids of the seeds of Eremostachys moluccelloides. Chem Nat Compd. 1978;14:33–6.CrossRefGoogle Scholar
  6. Parthibane V, Rajakumari S, Venkateshwari V, Iyappan R, Rajasekharan R. Oleosin is bifunctional enzyme that has both monoacylglycerol acyltransferase and phospholipase activities. J Biol Chem. 2012;287:1946–54.CrossRefPubMedGoogle Scholar
  7. Perry HJ, Harwood JL. Radiolabelling studies of acyl lipids in developing seeds of Brassica napus: use of [1-14C]-acetate precursor. Phytochemistry. 1993;33:329–33.CrossRefGoogle Scholar
  8. Petit J, Bres C, Mauxion JP, Tai FWJ, Martin LBB, Fich EA, Joubès J, Rose JKC, Domergue F, Rothan C. The glycerol-3-phosphate acyltransferase GPAT6 from tomato plays a central role in fruit cutin biosynthesis. Plant Physiol. 2016;171:894–913.PubMedPubMedCentralGoogle Scholar
  9. Reddy VS, Rao V, Rajasekharan R. Functional characterization of lysophosphatidic acid phosphatase from Arabidopsis thaliana. Biochim Biophys Acta. 2010;1801:455–61.CrossRefPubMedGoogle Scholar
  10. Shekar S, Tumaney AW, Rao TJVS, Rajasekharan R. Isolation of lysophosphatidic acid phosphatase from developing peanut cotyledons. Plant Physiol. 2002;128:988–96.CrossRefPubMedPubMedCentralGoogle Scholar
  11. Simpson JP, Ohlrogge JB. A novel pathway for triacylglycerol biosynthesis is responsible for the accumulation of massive quantities of glycerolipids in the surface wax of bayberry (Myrica pensylvanica) fruit. Plant Cell. 2016;28:248–64.PubMedPubMedCentralGoogle Scholar
  12. Stobart K, Mancha M, Lenman M, Dahlqvist A, Stymne S. Triacylglycerols are synthesised and utilized by transacylation reactions in microsomal preparations of developing safflower (Carthamus tinctorius L.) seeds. Planta. 1997;203:58–66.Google Scholar
  13. Tumaney AW, Shekar S, Rajasekharan R. Identification, purification and characterization of monoacylglycerol acyltransferase from developing peanut cotyledons. J Biol Chem. 2001;276:10847–52.PubMedGoogle Scholar
  14. Yang W, Pollard M, Li-Beisson Y, Beisson F, Feig M, Ohlrogge J. A distinct type of glycerol-3-phosphate acyltransferase with sn2- preference and phosphatase activity producing 2-monoacylglycerol. PNAS. 2010;107:12040–5.CrossRefPubMedPubMedCentralGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2017

Authors and Affiliations

  1. 1.Albrecht-von-Haller-Institute for Plant Sciences, Dept. of Plant BiochemistryGeorg-August-University GoettingenGoettingenGermany