Homeostasis is essential for muscle repair and regeneration after skeletal muscle exercise. This study investigated the role of methyltransferase-like 21C (METTL21C) in skeletal muscle of mice after exercise and the potential mechanism. First, muscle samples were collected at 2, 4, and 6 weeks after exercise, liver glycogen, muscle glycogen, blood lactic acid (BLA) and triglyceride (TG) were assessed. Moreover, the expression levels of autophagy markers and METTL21C in skeletal muscle were analyzed. The results showed that the expressions of METTL21C and MYH7 in the gastrocnemius muscle of mice in the exercise group were significantly higher than that in the control group after exercise, which suggested that long-term exercise promoted the formation of slow-twitch muscle fibers in mouse skeletal muscle. Likewise, the autophagy capacity is enhanced with the extension of exercise in muscles. The findings were further verified in mouse C2C12 cells. We discovered that knockdown of Mettl21c reduced the expression of MYH7 and autophagy level in mouse myoblasts. These findings indicate that METTL21C promotes skeletal muscle homeostasis after exercise by enhancing autophagy, while METTL21C also contributes to differentiation of myogenic and formation of slow muscle fiber.

Primula secundiflora is an insect-pollinated, perennial herb belonging to section Proliferae (Primulaceae) and exhibits considerable variation in mating system with predominantly outcrossing populations comprising long-styled and short-styled floral morphs and selfing populations comprising only homostyles. To facilitate future investigations of the population genetics and mating patterns of this species, we developed 25 microsatellite markers from P. secundiflora using next-generation sequencing and measured polymorphism and genetic diversity in a sample of 30 individuals from three natural populations. The markers displayed relatively high polymorphism, with the number of observed alleles per locus ranging from three to 16 (mean = 8.36). The observed and expected heterozygosities ranged from 0.100 to 1.000 and 0.145 to 0.843, respectively. Twenty-one of the loci were also successfully amplified in P. denticulata. These microsatellite markers could provide powerful tools for investigating patterns of population genetic diversity and the evolutionary relationships between distyly and homostyly in this species.