Heterologous Expression and Biochemical Characterization of Two Lipoxygenases in Oriental Melon, Cucumis melo var. makuwa Makino

PLoS One. 2016 Apr 21;11(4):e0153801. doi: 10.1371/journal.pone.0153801. eCollection 2016.

Abstract

Lipoxygenases (LOXs) are a class of non-heme iron-containing dioxygenases that catalyse oxidation of polyunsaturated fatty acids to produce hydroperoxidation that are in turn converted to oxylipins. Although multiple isoforms of LOXs have been detected in several plants, LOXs in oriental melon have not attracted much attention. Two full-length LOX cDNA clones, CmLOX10 and CmLOX13 which have been isolated from oriental melon (Cucumis melo var. makuwa Makino) cultivar "Yumeiren", encode 902 and 906 amino acids, respectively. Bioinformatics analysis showed that CmLOX10 and CmLOX13 included all of the typical LOX domains and shared 58.11% identity at the amino acid level with each other. The phylogenetic analysis revealed that CmLOX10 and CmLOX13 were members of the type 2 13-LOX subgroup which are known to be involved in biotic and abiotic stress. Heterologous expression of the full-length CmLOX10 and truncated CmLOX13 in Escherichia coli revealed that the encoded exogenous proteins were identical to the predicted molecular weights and possessed the lipoxygenase activities. The purified CmLOX10 and CmLOX13 recombinant enzymes exhibited maximum activity at different temperature and pH and both had higher affinity for linoleic acid than linolenic acid. Chromatogram analysis of reaction products from the CmLOX10 and CmLOX13 enzyme reaction revealed that both enzymes produced 13S-hydroperoxides when linoleic acid was used as substrate. Furthermore, the subcellular localization analysis by transient expression of the two LOX fusion proteins in tobacco leaves showed that CmLOX10 and CmLOX13 proteins were located in plasma membrane and chloroplasts respectively. We propose that the two lipoxygenases may play different functions in oriental melon during plant growth and development.

Publication types

  • Clinical Trial, Phase II
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Cucumis / enzymology*
  • DNA, Complementary
  • Lipoxygenase / chemistry
  • Lipoxygenase / genetics
  • Lipoxygenase / metabolism*
  • Sequence Homology, Amino Acid
  • Subcellular Fractions / enzymology

Substances

  • DNA, Complementary
  • Lipoxygenase

Grant support

This study was financially supported by the National Natural Science Foundation of China (31471868). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.