Salty Dog, an SLC5 Symporter, Modulates Drosophila Response to Salt Stress

Physiol Genomics. 2009 Mar 3;37(1):1-11. doi: 10.1152/physiolgenomics.90360.2008. Epub 2008 Nov 18.

Abstract

To regulate their internal environments, organisms must adapt to varying ion levels in their diet. Adult Drosophila were exposed to dietary salt stress, and their physiological, survival, and gene expression responses monitored. Insects continued to feed on NaCl-elevated diet, although levels >4% wt/vol ultimately proved fatal. Affymetrix microarray analysis of flies fed on diet containing elevated NaCl showed a phased response: the earliest response was widespread upregulation of immune genes, followed by upregulation of carbohydrate metabolism as the immune response was downregulated, then finally a switch to amino acid catabolism and inhibition of genes associated with the reproductive axis. Significantly, the online transcriptomic resource FlyAtlas reports that most of the modulated genes are predominantly expressed in hindgut or Malpighian (renal) tubule, implicating these excretory tissues as the major responders to salt stress. Three genes were selected for further study: the SLC5 symporter CG2196, the GLUT transporter CG6484, and the transcription factor sugarbabe (previously implicated in starvation and stress responses). Expression profiles predicted by microarray were validated by quantitative PCR (qPCR); expression was mapped to the alimentary canal by in situ hybridization. CG2196::eYFP overexpression constructs were localized to the basolateral membrane of the Malpighian (renal) tubules, and RNAi against CG2196 improved survival on high-salt diet, even when driven specifically to just principal cells of the Malpighian tubule, confirming both this tissue and this transporter as major determinants of survival upon salt stress. Accordingly, CG2196 was renamed salty dog (salt).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / metabolism
  • Carbohydrate Metabolism / drug effects
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Drosophila Proteins / metabolism*
  • Drosophila melanogaster / cytology
  • Drosophila melanogaster / drug effects*
  • Drosophila melanogaster / genetics
  • Drosophila melanogaster / physiology*
  • Feeding Behavior / drug effects
  • Gene Expression Regulation / drug effects
  • Genes, Insect
  • Humans
  • Ion Transport / drug effects
  • Luminescent Proteins / metabolism
  • Oligonucleotide Array Sequence Analysis
  • Organ Specificity / drug effects
  • Phylogeny
  • RNA Interference / drug effects
  • Reproducibility of Results
  • Sodium Chloride / pharmacology*
  • Sodium Chloride, Dietary / pharmacology
  • Stress, Physiological / drug effects*
  • Survival Analysis
  • Symporters / metabolism*
  • Time Factors

Substances

  • Bacterial Proteins
  • Drosophila Proteins
  • Luminescent Proteins
  • Sodium Chloride, Dietary
  • Symporters
  • yellow fluorescent protein, Bacteria
  • Sodium Chloride