Differential expression of duplicated LDH‐A genes during temperature acclimation of weatherfishMisgurnus fossilis

Abstract

Temperature acclimation in poikilotherms entails metabolic rearrangements provided by variations in enzyme properties. However, in most cases the underlying molecular mechanisms that result in structural changes in the enzymes are obscure. This study reports that acclimation to low (5 °C) and high (18 °C) temperatures leads to differential expression of alternative forms of the LDH‐A gene in white skeletal muscle of weatherfish, Misgurnus fossilis. Two isoforms of LDH‐A mRNA were isolated and characterized: a short isoform (= 1332 bp) and a long isoform ( = 1550 bp), which both have 5′‐UTRs and ORFs of the same length (333 amino acid residues), but differ in the length of the 3′‐UTR. In addition, these two mRNAs have 44 nucleotide point mismatches of an irregular pattern along the complete sequence, resulting in three amino acid mismatches (Gly214Val; Val304Ile and Asp312Glu) between protein products from the short and long mRNA forms, correspondingly LDH‐Aα and LDH‐Aβ subunits. It is expected that the β‐subunit is more aliphatic due to the properties of the mismatched amino acids and therefore sterically more restricted. According to molecular modelling of M. fossilis LDH‐A, the Val304Ile mismatch is located in the subunit contact area of the tetramer, whereas the remaining two mismatches surround the contact area; this is expected to manifest in the kinetic and thermodynamic properties of the assembled tetramer. In warm‐acclimated fish the relative expression between α and β isoforms of the LDH‐A mRNA is around 5 : 1, whereas in cold‐acclimated fish expression of is reduced almost to zero. This indicates that at low temperature the pool of total tetrameric LDH‐A is more homogeneous in terms of α/β‐subunit composition. The temperature acclimation pattern of proportional pooling of subunits with different kinetic and thermodynamic properties of the tetrameric enzyme may result in fine‐tuning of the properties of skeletal LDH‐A, which is in line with previously observed kinetic and thermodynamic differences between ‘cold’ and ‘warm’ LDH‐A purified from weatherfish. Also, an irregular pattern of nucleotide mismatches indicates that these mRNAs are the products of two independently evolving genes, i.e. paralogues. Karyotype analysis has confirmed that the experimental population of M. fossilis is tetraploid (2n = 100), therefore gene duplication, possibly through tetraploidy, may contribute to the adaptability towards temperature variation.

Isolation and molecular characterization of Rem2 isoforms in the rainbow trout (Oncorhynchus mykiss): Tissue and central nervous system expression

“…The presence of Rem2 isoforms in rainbow trout is not unexpected as salmonids are well-known to possess isoforms implicated as the result of gene duplication (Moore et al, 1999; Doyon et al, 2003; Englesma et al, 2003; Richards et al, 2003; Koskinen et al, 2004; Gabillard et al, 2006; Quezada et al, 2006; Gharbi et al, 2007; Negler et al, 2007; Ostbye et al, 2007; Saito et al, 2007; Zakhartsev et al, 2007; Chondrou et al, 2008; Hansson and Hahn, 2008; Guo et al, 2009; Østergaard et al, 2009; Morash et al, 2010). REM2 was first described in mammals (Finlin et al, 2000), and has since been isolated in fish (Edel et al 2010b).…”

Heat Shock Proteins and Whole Body Adaptation to Extreme Environments

“…Such isoforms were described for acetylcholine esterase, ferritin, choline esterase, LDH and many other enzymes (see Zakhartsev et al 2007 ). Such isoforms were described for acetylcholine esterase, ferritin, choline esterase, LDH and many other enzymes (see Zakhartsev et al 2007 ).…”

Ambient temperature as a factor contributing to the developmental divergence in sympatric salmonids

“…The ambient temperature strongly affects the level of metabolic activity and oxygen consumption of poikilothermic animals [21][22][23][24][25]. It regulates such vital biological processes as transcription and chromatin organization [26][27][28][29], catalytic activity and enzyme folding [30][31][32]. Hence, it largely orchestrates the process of adaptive specialization in the heterogeneous environment.…”