Strigolactones (SLs) are carotenoid-derived phytohormones and rhizosphere signaling molecules for arbuscular mycorrhizal fungi and root parasitic weeds. Why and how plants produce diverse SLs are unknown. Here, cytochrome P450 CYP722C is identified as a key enzyme that catalyzes the reaction of BC-ring closure leading to orobanchol, the most prevalent canonical SL. The direct conversion of carlactonoic acid to orobanchol without passing through 4-deoxyorobanchol is catalyzed by the recombinant enzyme. By knocking out the gene in tomato plants, orobanchol was undetectable in the root exudates, whereas the architecture of the knockout and wild-type plants was comparable. These findings add to our understanding of the function of the diverse SLs in plants and suggest the potential of these compounds to generate crops with greater resistance to infection by noxious root parasitic weeds.
An increase in red blood cells (RBCs) is believed to improve exercise performance, because RBCs transport O 2 from the lungs to the tissues and deliver metabolically produced CO 2 to the lungs for expiration. In this study, we examined the effects of increased or decreased RBCs on exercise performance in mice. In order to vary the volume percentage of RBCs in blood (hematocrit levels), trained FVB mice were administered darbepoetin alfa (DPA), a long-acting erythropoiesis-stimulating agent, or phenylhydrazine (PHZ), a reagent inducing hemolytic anemia. The exercise performance was evaluated using a forced swimming pool. The administration of DPA or PHZ caused a significant increase or decrease in hematoctit levels, respectively. However, the partial improvement in exercise performance due to increased RBCs was observed only when higher intensity exercise was applied to mice whose hematocrit levels exceeded 70%. In addition, the decrease in exercise performance due to decreased RBCs was limited, even when the hematocrit levels was about 35%. These results suggested that the increase or decrease in RBCs had little effect on exercise performance in mice.
Background: There is growing demand for evaluation of the effects of supplements on endurance capacity or physical fatigue. In many cases, this has been conducted by the treadmill test or forced swimming test for rodents, in which the time until fatigue is recorded. However, there are some problems, including the large variation of data, the excessive stress on experimental animals and the unpredictable finish time of each test. In this study, we attempted to establish a new evaluation method for endurance capacity in mice. Methods: Seven-week-old FVB mice were subjected either to a sedentary existence or forced wheel-running (1h/day) with and without a doping drug, including darbepoetin alfa (DPO: 10 μg/kg/week) and clenbuterol (CLE: 2 mg/kg/day), for 4 weeks. At 2 and 4 weeks treatment, we subjected mice to a forced swimming test, using a counter current swimming pool, in which the number of times that mice passed at a distance 35 cm from nozzle was counted every 10 min for 30 min. Results: FVB mice showed high compliance to the forced exercises, which was associated with the small variation of data. In all tested groups, the number of times at a distance 35 cm was most frequently in the first 10 min and decreased timedependently. Exercise training significantly prevented weight gain, but had no effect on endurance capacity. DPO treatment significantly increased hematocrit, but did not affect endurance performance. On the other hand, CLE treatment markedly decreased endurance capacity. Conclusions: We could evaluate the physical fatigue by counting the number of times at a distance 35 cm. The fixed duration of each test alleviated a burden on experimental animals and researchers. The results of DPO and CLE on endurance capacity were unexpected, but not inconsistent with previous reports. Therefore, our new method was considered to be useful for the evaluation of endurance capacity of mice.
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