Mitochondria from the salt-tolerant yeast Debaryomyces hansenii (halophilic organelles?)

Abstract

The yeast Debaryomyces hansenii is considered a marine organism. Sea water contains 0.6 M Na(+) and 10 mM K(+); these cations permeate into the cytoplasm of D. hansenii where proteins and organelles have to adapt to high salt concentrations. The effect of high concentrations of monovalent and divalent cations on isolated mitochondria from D. hansenii was explored. As in S. cerevisiae, these mitochondria underwent a phosphate-sensitive permeability transition (PT) which was inhibited by Ca(2+) or Mg(2+). However, D. hansenii mitochondria require higher phosphate concentrations to inhibit PT. In regard to K(+) and Na(+), and at variance with mitochondria from all other sources known, these monovalent cations promoted closure of the putative mitochondrial unspecific channel. This was evidenced by the K(+)/Na(+)-promoted increase in: respiratory control, transmembrane potential and synthesis of ATP. PT was equally sensitive to either Na(+) or K(+). In the presence of propyl-gallate PT was still observed while in the presence of cyanide the alternative pathway was not active enough to generate a Delta Psi due to a low AOX activity. In D. hansenii mitochondria K(+) and Na(+) optimize oxidative phosphorylation, providing an explanation for the higher growth efficiency in saline environments exhibited by this yeast.

The role of mitochondria in plant development and stress tolerance

“…Studies in other yeast species also demonstrate the importance of mitochondria in adaptation to the environment. For example, in contrast to non-marine yeast species, Debaryomyces hansenii (halophilic marine yeast) MUCs close in response to Na + and K + under high salinity conditions therefore increasing transmembrane potential and ATP synthesis (CABRERA-OREFICE et al 2010). Consequently, we can infer that this shift in MUC function drove the adaptation of D. hansenii to saline environments.…”

High Osmolarity Environments Activate the Mitochondrial Alternative Oxidase in Debaryomyces Hansenii

“…A RCR of 4–5 using pyruvate/malate/citrate was usually obtained using this isolation protocol. Alternatively, mitochondria were isolated after cell lysis with glass beads in a bead beater at a constant rheostat level as in [10], with similar results in quality.…”

“…In addition, the membrane potential in isolated mitochondria was also determined as in [10] using 10 mM pyruvate/malate/citrate as substrates. Where indicated, 100 μM KCN, 1 μM propyl gallate, 100 μM SHAM or 10 μM carbonyl cyanide m-chlorophenyl hydrazone (CCCP) was added to the incubation media.…”

The mitochondrial permeability transition from yeast to mammals

“…Most classical studies of the PT were carried out in mitochondria obtained from mammals, although permeability changes, most notably those caused by ATP and substrates, have also been studied in yeast [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. In recent years, the growing interest on the PT in cell death has prompted an increasing number of studies in mitochondria from other organisms including plants [56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71], fish [72,73], amphibians [74,75], and the brine shrimp Artemia franciscana, a salt-and anoxia-tolerant organism that may represent an exception in that it apparently lacks a PT [76].…”