Differential Expressions Of Energy Metabolism-related Genes Among Different Periods In Bufo Gargarizans

Life history strategies reflect variation in the allocation of individual’s resources(i.e.,time,energy expenditure)to individual’s life activity(i.e.,growth,survival and reproduction).Life history theory is concerned with variation in investment in different components of the life cycle within species.It is a challenging issue for animals to weigh the benefits of growth and survival,wintering and survival,survival and reproduction,and to quantitatively quantify energy intake,storage and distribution.The study of energy allocation strategies helps understanding the life history of animals.Most of researches on animal energy allocation strategies have been mostly focused on mammals,and birds.There are few studies on amphibians.The Asiatic toad,Bufo gargarizans,is an amphibian species widely distributed in China.B.gargarisans has a yearly seasonal activity that has an active period before hibernation,hibernating period during cold months,after which the species become active with body awakening,and begins reproducing after emergence,and re-entry into active period after the mating period.Research on B.gargarzizans mainly focuses on the species’ medicinal value,hormone regulation,embryo development,etc.There are less research on life history and energy allocation strategy.This study analyzes the energy allocation strategies of B.gargarizans among different periods.Animals’ adaptation to the environment is achieved by changing the expression pattern of genes.Through the study of the differences in animal and energy metabolism related gene expression patterns,the changes in energy input and expenditure are obtained.The study on the difference of expression levels of genes related to animal and energy metabolism in different periods is an important method for energy allocation strategy research.AMPK signaling pathway is the main way to regulate energy homeostasis.We used the differences in the transcription levels of energy metabolism-related genes in AMPK signaling pathway to explore the energy allocation strategies of each activity period in B.gargarizans.The obtained results can be summarized as the following:(1)FOXO1,PEPCK,PGC1α,CREB1,GSK3a,GSK3b,GP,ACL,DGAT1,FAS,GPAT3,GPD1,LPL,FAE were the genes associated with energy reserves,which revealed significant differences in expression levels among different activity periods of B.gargarizans(P<0.05).We considered that these energy-related genes participate in the energy reserve of B.gargarizans’ periodical behaviors.ENO1,LDHA,PGK1,PK,TPI,PFKL,ACADM,ACOX1,HADHA,HSL,SCP2,UCP2,AMPK2 were the genes associated with energy consumption,which exhibited significant differences in expression levels across diffrent activity periods of B.gargarizans(P<0.05).We considered that these energy-related genes participate in the energy allocation of B.gargarizans’s seasonal activities.(2)There were differences in the expression levels of energy-reserving and energy-consuming genes between males and females in different activity periods(P<0.05).It was speculated that the difference in physiological functions between the two sexes is one of the reasons for the difference in energy reserve and energy distribution between males and females in B.gargarizans.(3)Compared with the active phase,the expression level of energy metabolism-related genes in the AMPK signaling pathway of B.gargarizans in the hibernation period showed a decreasing trend but have no significant differences(P>0.05).Metabolism has down-regulation in B.gargarizans during hibernation.It was speculated that the wintering energy distribution strategy of B.gargarizans is a reduction in metabolism and energy consumption.(4)Compared with the hibernation phase,there was no significant difference in the expression levels of energy metabolism-related genes in the AMPK signaling pathway of B.gargarizans in the expiration period(P>0.05).B.gargarizans may have similar activities and energy intake during the hibernation period.It is speculated that B.gargarizans have awakening,habitat replacement,and energy supplementation during hibernation.(5)Compared with the expiration phase,significantly increased expression levels of energy metabolism-related genes in the AMPK signaling pathway of B.gargarizans in the before breeding period(P<0.05).Energy reserve and energy consumption has up-regulation in B.gargarizans before breeding.There was a significantly negative correlation between the number of eggs for the mating pairs and the weight of the corresponding offspring(R2=0.2322,P=0.001).It is speculated that the energy reserve of B.gargarizans before breeding can’t guarantee the number of eggs and the quality of the offspring at the same time,and may add a small amount of energy to improve the reproductive success rate before breeding.(6)Compared with the before-breeding phase,there were significantly decreased expression levels of energy metabolism-related genes in the AMPK signaling pathway of B.gargarizans in the after mating period(P<0.05).It was speculated that there is no energy intake and a lot of energy consumption during the breeding period of B.gargarizans.Generally,our results showed that:(1)Physiological strategy during wintering for B.gargarizans is reducing metabolism level and energy consumption,with wintering energy coming from a large amount of energy reserves untaken before hibernation,and a small amount of energy supplement.(2)Higher energy consumption and no energy intake during the breeding period,with reproductive energy coming from the body’s reserves and energy supplement accumulated before the breeding period.Our research provides information on the understanding of amphibian seasonal energy allocation strategies,and provides novel scientific methods for the study of life history of amphibians.