No abstract

No abstract

The innate immune system of plants is crucial in defining the fate of a plant cell during plant–pathogen interactions. This response is often accompanied by a hypersensitive reaction leading to the death of a plant cell and restricted pathogen growth. Plant mitochondria, in this case, play a key role by maintaining a balance between cell respiration and reactive oxygen species formation. One of the key features of the hypersensitive response is the shift of the normal plant respiratory pathway to a special ‘alternative’ pathway. Plants contain an enzyme, alternative oxidase, for maintaining metabolic homeostasis of the cell. This energy dissipating respiration provides a branch in normal respiration by using ubiquinone to form water and heat, thus maintaining the energy status of the cell. Alternative oxidase is thought to minimize production of reactive oxygen species and can also function in ‘anti‐apoptotic’ machinery in plant cells. In this mini review, we briefly describe the alternative respiratory pathway and explain the role of alternative oxidase in important cellular processes, such as programmed cell death and the hypersensitive response.

Cyanide-resistant respiration in potato mitochondria is an important pathway for energy dissipation. It can be activated by high light; however, it is unclear what roles cyanide-resistant respiration plays in the response to high light stress in potato.• We designed a CRISPR vector for the functional gene StAOX of the potato cyanide-resistant respiratory pathway. Agrobacterium tumefaciens GV3101 was transformed into potato. Hydrogen peroxide level, MDA content, antioxidant activity and cyanide-resistant respiratory capacity of potato leaves under high light stress were determined. Photosynthetic efficiency and chlorophyll content were determined. In addition, the operation of the malate-oxaloacetate shuttle route and transcription level of photorespiration-related enzymes were also examined.• The results showed that two base substitutions occurred at the sequencing target site on leaves of the transformed potato. Accumulation of ROS and increased membrane lipid peroxidation were detected in the transformed potato leaves and lower photosynthetic efficiency was observed. The transcription level of the malate-oxaloacetate shuttle route and photorespiration-related enzymes also significantly increased.• These results indicate that the cyanide-resistant respiration is an important physiological pathway in potato in response to high light stress. It also suggests that plant cyanide-resistant respiration is closely related to photosynthesis. This implies the unexplored importance of plant cyanide-resistant respiration in plant photosynthesis, energy conversion and carbon skeleton formation.Plant Biology 22 (2020) 425-432

HM-3, an integrin antagonist, exhibits anti-tumor biological responses and therefore has potential as a therapeutic polypeptide. However, the clinical applications of HM-3 are limited by its short half-life. In this study, we genetically fused human serum albumin (HSA) to the N or C-terminus of HM-3 to improve HM-3 pharmacokinetics. HM-3/HSA proteins were successfully expressed in Pichia pastoris and displayed improved pharmacokinetic properties and stability. Among them, the half-life of HM-3-HSA was longer than HSA-HM-3. In vitro, the IC50 values of HSA-HM-3 and HM-3-HSA were 0.38 ± 0.14 μM and 0.25 ± 0.08 μM in B16F10 cells, respectively. In vivo, the inhibition rates of B16F10 tumor growth were 36% (HSA-HM-3) and 56% (HM-3-HSA), respectively, indicating antitumor activity of HM-3-HSA was higher than HSA-HM-3. In conclusion, these results suggested that the HM-3/HSA fusion protein might be potential candidate HM-3 agent for treatment of melanoma and when HSA was fused at the C-terminus of HM-3, the fusion protein had a higher stability and activity.

The significance of alternative respiratory pathway (AOXs) during the interaction between soft rot bacteria (Pectobacterium carotovorum subsp. carotovorum, (Pcc.)) and potato tubers is well-defined. However, the role of the AOXs in impaired mitochondrial respiratory chain function during the Pcc. infection is yet to be studied. In this study, the results show that with the aggravation of infection of Pcc., the capacity for alternative respiration in mitochondria of potato tubers increased gradually. The mitochondrial membrane potential increased more significantly after infection with Pcc. when the AOXs in potato tubers was partially blocked using salicylhydroxamic acid (SHAM) beforehand. In addition, the activity of complex III decreased more drastically while the activity of complex IV increased more significantly in the partial absence of the AOXs in the mitochondria. Furthermore, the mitochondrial endogenous respiration, mitochondrial respiratory state 3 and respiratory control rate (RCR) decreased more significantly and the value of RCR reached around 1.0 with the aggravation of infection of Pcc. in the partially absence of AOXs in the mitochondria.