The crucial role of mitochondrial regulation in adaptive aluminium resistance in Rhodotorula glutinis

Abstract

Rhodotorula glutinis IFO1125 was found to acquire increased aluminium (Al) resistance from 50 mM to more than 5 mM by repetitive culturing with stepwise increases in Al concentration at pH 4.0. To investigate the mechanism underlying this novel phenomenon, wild-type and Alresistant cells were compared. Neither cell type accumulated the free form of Al (Al 3+ ) added to the medium. Transmission electron microscopic analyses revealed a greater number of mitochondria in resistant cells. The formation of small mitochondria with simplified cristae structures was observed in the wild-type strain grown in the presence of Al and in resistant cells grown in the absence of Al. Addition of Al to cells resulted in high mitochondrial membrane potential and concomitant generation of reactive oxygen species (ROS). Exposure to Al also resulted in elevated levels of oxidized proteins and oxidized lipids. Addition of the antioxidants a-tocopherol and ascorbic acid alleviated the Al toxicity, suggesting that ROS generation is the main cause of Al toxicity. Differential display analysis indicated upregulation of mitochondrial genes in the resistant cells. Resistant cells were found to have 2.5-to 3-fold more mitochondrial DNA (mtDNA) than the wild-type strain. Analysis of tricarboxylic acid cycle and respiratory-chain enzyme activities in wild-type and resistant cells revealed significantly reduced cytochrome c oxidase activity and resultant high ROS production in the latter cells. Taken together, these data suggest that the adaptive increased resistance to Al stress in resistant cells resulted from an increased number of mitochondria and increased mtDNA content, as a compensatory response to reduced respiratory activity caused by a deficiency in complex IV function.

Bioanalysis of Eukaryotic Organelles

“…The effects of aluminum exposure on mitochondrial activity was determined in R. glutinis aluminum-sensitive and aluminum-insensitive cells. 543 Aluminum insensitive cells were developed with constant aluminum treatment. Transmission electron microscopy demonstrated that aluminum-insensitivity was associated w ith increased the number of mitochondria, which were smaller and had simplified cristae.…”

Molecular Basis of Aluminium Toxicity in Plants: A Review

“…A recent study demonstrated that Rhodotorulaglutinis has 2.5 to 3 folds more mitochondria in Al-resistant yeast strain than the wild-type strain [68]. The Mg 2+ ions are essential for normal functioning of mitochondria as their deficiency often results in mitochondrial disintegration [69], reactive oxygen species (ROS) production, and photo-oxidative damage in many plant species [70].…”

Characterization of calcineurin from Cryptococcus humicola and the application of calcineurin in aluminum tolerance

“…Several studies have demonstrated that signal pathways are involved in Al tolerance in S. cerevisiae and R. glutinis , including the SLT2 mitogen-activated protein kinase signal transduction pathway, the calmodulin-dependent protein phosphatase (calcineurin) signaling pathways and the calmodulin-dependent protein kinase [30, 33, 34]. Cyclosporin A is an inhibitor of calcineurin.…”