Hypoxia up-regulates mitochondrial genome-encoded transcripts in Arabidopsis roots

Plants are frequently exposed to limitations in oxygen availability during their lifetime. During evolution, they have developed a number of physiological and morphological adaptations to tolerate oxygen and other stress conditions. These include regulation of growth by gene expression and ATP generation. The regulation of nuclear genes after hypoxia and anoxia is well studied; however, the regulation of mitochondrial genes in response to oxygen stress has not been characterized to date. Therefore, we have established an Arabidopsis mitochondrial genome-specific microarray that accommodates probes for all mitochondrial DNA-encoded genes and conserved open reading frames. Our analysis showed an up-regulation of mitochondrial transcripts in Arabidopsis roots after 48 h of hypoxia. Since no significant difference was detected in the expression of mitochondrial RNA polymerases or the mitochondrial DNA content per cell, we propose a transcriptional mode of induction of mitochondrial gene expression under hypoxia.