Arabidopsis mtHSC70-1 plays important roles in the establishment of COX-dependent respiration and redox homeostasis

Abstract

The 70 kDa heat shock proteins function as molecular chaperones and are involved in diverse cellular processes. However, the functions of the plant mitochondrial HSP70s (mtHSC70s) remain unclear. Severe growth defects were observed in the Arabidopsis thaliana mtHSC70-1 knockout lines, mthsc70-1a and mthsc70-1b. Conversely, the introduction of the mtHSC70-1 gene into the mthsc70-1a background fully reversed the phenotypes, indicating that mtHSC70-1 is essential for plant growth. The loss of mtHSC70-1 functions resulted in abnormal mitochondria and alterations to respiration because of an inhibition of the cytochrome c oxidase (COX) pathway and the activation of the alternative respiratory pathway. Defects in COX assembly were observed in the mtHSC70-1 knockout lines, leading to decreased COX activity. The mtHSC70-1 knockout plants have increased levels of reactive oxygen species (ROS). The introduction of the Mn-superoxide dismutase 1 (MSD1) or the catalase 1 (CAT1) gene into the mthsc70-1a plants decreased ROS levels, reduced the expression of alternative oxidase, and partially rescued growth. Taken together, our data suggest that mtHSC70-1 plays important roles in the establishment of COX-dependent respiration.

Molecular and physiological responses during thermal acclimation of leaf photosynthesis and respiration in rice

“…Alternatively, a reduction in COX might be a consequence of heat directly interfering with its synthesis. In support of this, a recent report shows that COX abundance and capacity in Arabidopsis is significantly reduced by knocking out an HSP70 isoform, suggesting that heat in some way interacts with COX formation (Wei et al, ).…”

Responses of leaf respiration to heatwaves

“…HSPs also appear to provide protection from ROS damage. Arabidopsis mitochondrial HSP70 knockout lines have severely reduced growth, increased ROS and impaired COX assembly and activity (Wei et al, 2019), emphasizing the importance of HSP70 in maintaining COX and limiting ROS production. Supplementation of apple ( Pyrus pumila [Mill.]…”

Arabidopsis mtHSC70-1 physically interacts with the Cox2 subunit of cytochrome c oxidase

“…2 In our first paper on mtHSC70-1, we demonstrated that Arabidopsis mtHSC70-1 plays important roles in the establishment of COX-dependent respiration and redox homeostasis. Using blue native-polyacrylamide gel electrophoresis and a polyclonal anti-Cox2 antibody, we found that the abundance of complex IV/COX was markedly lower in the mtHSC70-1 mutants compared to WT plants, 14 indicating that the Cox2 level in COX was reduced by the mtHSC70-1 knockout. Using real-time PCR and immunoblotting, we found that the levels of Cox2 mRNA and total Cox2 protein were not obviously downregulated by the mtHSC70-1 knockout, 14 suggesting that the stability of COX or the availability of Cox2 was impaired in the mtHSC70-1 mutants.…”

“…Using blue native-polyacrylamide gel electrophoresis and a polyclonal anti-Cox2 antibody, we found that the abundance of complex IV/COX was markedly lower in the mtHSC70-1 mutants compared to WT plants, 14 indicating that the Cox2 level in COX was reduced by the mtHSC70-1 knockout. Using real-time PCR and immunoblotting, we found that the levels of Cox2 mRNA and total Cox2 protein were not obviously downregulated by the mtHSC70-1 knockout, 14 suggesting that the stability of COX or the availability of Cox2 was impaired in the mtHSC70-1 mutants. To address the role of mtHSC70-1 in the assembly of Cox2 into COX, we tested the interaction between mtHSC70-1 and Cox2 using the following three techniques.…”

“…It has been reported that the expression patterns of these two genes are markedly different from each other. 14 We asked what causes functional divergence of these two mtHSC70 proteinsthe differences in amino acid sequences or the differences in gene expression patterns. This is a question that we are very interested in, and it is one of the questions we will study in the future.…”