Proline biosynthesis genes and their regulation under salinity stress in the euryhaline copepod Tigriopus californicus

Comp Biochem Physiol B Biochem Mol Biol. 2002 Aug;132(4):739-50. doi: 10.1016/s1096-4959(02)00091-x.


Diverse organisms regulate concentrations of intracellular organic osmolytes in response to changes in environmental salinity or desiccation. In marine crustaceans, accumulation of high concentrations of proline is a dominant component of response to hyperosmotic stress. In the euryhaline copepod Tigriopus californicus, synthesis of proline from its metabolic precursor glutamate is tightly regulated by changes in environmental salinity. Here, for the first time in a marine invertebrate, the genes responsible for this pathway have been cloned and characterized. The two proteins display the sequence features of homologous enzymes identified from other eukaryotes. One of the cloned genes, delta1-pyrroline-5-carboxylase reductase (P5CR), is demonstrated to have the reductase enzyme activity when expressed in proline-auxotroph bacteria, while the second, delta1-pyrroline-5-carboxylase synthase (P5CS), does not rescue proline-auxotroph bacteria. In contrast to results from higher plants, neither levels of P5CS nor P5CR mRNAs increase in response to salinity stress in T. californicus. Hence, regulation of proline synthesis during osmotic stress in T. californicus is likely mediated by some form of post-transcriptional regulation of either P5CS or P5CR. Understanding the regulation this pathway may elucidate the mechanisms limiting the salinity ranges of marine taxa.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Copepoda / enzymology
  • Copepoda / genetics
  • Copepoda / physiology*
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism
  • Fresh Water
  • Gene Expression Regulation*
  • Humans
  • Molecular Sequence Data
  • Ornithine-Oxo-Acid Transaminase / genetics
  • Ornithine-Oxo-Acid Transaminase / metabolism
  • Osmolar Concentration
  • Proline / biosynthesis*
  • Proline / genetics*
  • Pyrroline Carboxylate Reductases / genetics
  • Pyrroline Carboxylate Reductases / metabolism
  • RNA, Messenger / metabolism
  • Seawater
  • Sequence Alignment
  • Sequence Homology, Amino Acid


  • Drosophila Proteins
  • RNA, Messenger
  • Proline
  • Pyrroline Carboxylate Reductases
  • Ornithine-Oxo-Acid Transaminase