Feng Hanqing

The expression, function and regulation of mitochondrial alternative oxidase under biotic stresses.

To survive, plants possess elaborate defence mechanisms to protect themselves against virus or pathogen invasion. Recent studies have suggested that plant mitochondria may play an important role in host defence responses to biotic stresses. In contrast with animal mitochondria, plant mitochondria possess a unique respiratory pathway, the cyanide-insensitive alternative pathway, which is catalysed by the alternative oxidase (AOX). Much work has revealed that the genes encoding AOX, AOX protein and the alternative respiratory pathway are frequently induced during plant-pathogen (or virus) interaction. This raises the possibility that AOX is involved in host defence responses to biotic stresses. Thus, a key to the understanding of the role of mitochondrial respiration under biotic stresses is to learn the function and regulation of AOX. In this article, we focus on the theoretical and experimental progress made in the current understanding of the function and regulation of AOX under biotic stresses. We also address some speculative aspects to aid further research in this area.

Revisiting the Mesosome as a Novel Site of Hydrogen Peroxide Accumulation in Escherichia coli

The major source of endogenous hydrogen peroxide is generally thought to be the respiratory chain of bacteria and mitochondria. In our previous works, mesosome structure was induced in cells during rifampicin effect, and the mesosome formation is always accompanied by excess hydrogen peroxide accumulation in bacterial cells. However, the underlying mechanisms of hydrogen peroxide production and the rationale behind it remain still unknown. Here we report that hydrogen peroxide can specifically accumulate in the mesosome in vitro. Mesosomes were interpreted earlier as artifacts of specific cells under stress through TEM preparation, while, in the current study, mesosomes were shown as intracellular compartments with specific roles and features by using quickly freezing preparation of TEM. Formation of hydrogen peroxide was observed in suspension of mesosomal vesicles by using either a fluorescence-based reporter assay or a histochemical method, respectively. Our investigation provides experimental evidence that mesosomes can be a novel site of hydrogen peroxide accumulation.

Erratum to: Revisiting the Mesosome as a Novel Site of Hydrogen Peroxide Accumulation in Escherichia coli

The major source of endogenous hydrogen peroxide is generally thought to be the respiratory chain of bacteria and mitochondria. In our previous works, mesosome structure was induced in cells during rifampicin effect, and the mesosome formation is always accompanied by excess hydrogen peroxide accumulation in bacterial cells. However, the underlying mechanisms of hydrogen peroxide production and the rationale behind it remain still unknown. Here we report that hydrogen peroxide can specifically accumulate in the mesosome in vitro. Mesosomes were interpreted earlier as artifacts of specific cells under stress through TEM preparation, while, in the current study, mesosomes were shown as intracellular compartments with specific roles and features by using quickly freezing preparation of TEM. Formation of hydrogen peroxide was observed in suspension of mesosomal vesicles by using either a fluorescence-based reporter assay or a histochemical method, respectively. Our investigation provides experimental evidence that mesosomes can be a novel site of hydrogen peroxide accumulation.

Effects of extracellular ATP on the characteristics of photochemical reaction in bean (Phaseolus vulgaris) leaves under different light intensities

Aims Although adenosine 5′-triphosphate (ATP) is usually considered to be localized in intracellular spaces, plant and animal cells can secrete ATP from the cytosol into the extracellular matrix. This extracellular ATP (eATP) is an important signal molecule for many physiological responses in plants. However, whether eATP could also have effects on photosynthesis in plants has not been extensively studied. Methods With bean (Phaseolus vulgaris) leaves as experiment material, the effects of eATP on the chlorophyll fluorescence characteristics and photosynthetic O2 evolution rate were studied under different light intensities. Important findings The maximal photosystem II (PSII) quantum yield in light adaptation (Fv′/Fm′), effective photochemical quantum yield of PSII (Y(II)), and photochemical quenching coefficient (qP) gradually decreased, and the electron transport rate (ETR), non-photochemical quenching coefficient (qN), and the quantum yield of regulated energy dissipation (Y(NPQ)) increased, with increases in light intensity. Treatment of leaves with eATP significantly increased the values of the potential maximal photochemical efficiency of PSII (Fv/Fm), Fv′/Fm′, Y(II), qP, ETR, and photosynthetic O2 evolution rate, but did not affect the values of qN and Y(NPQ). In contrast, treatment of leaves with β,γ-methyleneadenosine triphosphate (AMP-PCP, an inhibitor of eATP receptors) significantly reduced the values of Fv/Fm, Fv′/Fm′, Y(II), ETR, and photosynthetic O2 evolution rate, but increased the values of qN and Y(NPQ). These results show that the levels of eATP exert important influences on the photochemical reaction in photosynthesis.