华南鲤昼夜摄食节律与agrp基因表达水平相关性研究

Relationship between diurnal feeding rhythm and agrp gene expression level in Cyprinus carpio rubrofuscus

鱼类的摄食节律表现出种间甚至种内差异。为阐明华南鲤(Cyprinus carpio rubrofuscus)的昼夜摄食节律,为其室内标准化养殖方法的建立提供科学依据,研究了在自然光照下华南鲤的昼夜摄食节律以及刺鼠相关蛋白(Agouti-related protein,AgRP)基因表达水平与摄食昼夜节律的关系。采用分段连续投喂的方法对春分和秋分时节广州地区华南鲤的昼夜摄食量进行测定,运用实时荧光定量PCR(Quantitative real-time PCR,qRT-PCR)技术检测agrp基因在华南鲤脑、前肠、中肠和后肠中的昼夜表达节律特点。结果显示,春分和秋分时节华南鲤摄食量有相似的昼夜节律。春分时华南鲤的摄食量在8:00最低,分别在12:00和24:00出现摄食高峰;秋分时华南鲤的摄食量也在8:00最低,分别在12:00和20:00出现摄食高峰。qRT-PCR结果表明,agrp1和agrp2基因的表达量都具有昼夜节律。agrp1和agrp2在脑中的表达量分别在8:00和20:00最高,24:00和4:00最低。agrp1基因在前肠、中肠和后肠的表达量分别在16:00、20:00和24:00最高,8:00最低;agrp2基因在前、中、后肠的表达量分别在16:00、24:00、24:00最高,在12:00、4:00、20:00最低。综上,华南鲤摄食量最低时agrp1基因在脑中的表达量最高以促进后续摄食行为,在2次摄食高峰之间(12:00—20:00)agrp1基因在前、中、后肠的表达量依次出现最高点,其变化趋势与食物在肠道中的运动过程一致,推测agrp1基因可能参与了华南鲤摄食昼夜节律的调控;而agrp2基因的表达水平与摄食节律无相关的变化趋势,推测agrp2基因在进化过程中可能出现了功能分化。

Feeding rhythms in fish show inter-and even intra-species variation.In order to detect the circadian feeding rhythm of Cyprinus carpio rubrofuscus and to provide a scientific basis for the establishment of standardized indoor aquaculture me-thods,we investigated the circadian feeding rhythm of C.carpio rubrofuscus and the relationship between the expression level of Agouti-related protein(AgRP)gene and circadian feeding rhythm under natural light.Besides,we measured the food intake of C.carpio rubrofuscus during the spring and autumn equinoxes in Guangzhou by segmented continuous feeding.We applied quantitative real-time PCR(qRT-PCR)to characterize the circadian expression profile of agrp genes in its brain,foregut,midgut and hindgut.The results show that the food intake of C.carpio rubrofuscus had a similar circadian rhythm,lowest at 8:00 in both spring and autumn equinoxes.Two feeding peaks appeared at 12:00 and 24:00 in spring equinox,and appeared at 12:00 and 20:00 in the autumn equinox.The qRT-PCR results show that the expressions of agrp1 and agrp2 genes had circadian rhythms,highest at 8:00 and 20:00 but lowest at 24:00 and 4:00 in brain.In foregut,midgut and hindgut,the highest agrp1 expression levels were observed at 16:00,20:00 and 24:00,respectively,but the lowest level was observed at 8:00.The highest agrp2 expres-sion levels were observed at 16:00,24:00 and 24:00,but the lowest levels were observed at 12:00,4:00 and 20:00.In conclusion,when the feeding intake level of C.carpio rubrofuscus was the lowest,the agrp1 gene had the highest expression level in brain to promote subsequent feeding behavior.Between the two feeding peaks(12:00-20:00),the expression levels of agrp1 reached the maximum in foregut,midgut and hindgut in turn.This trend was consistent with the movement of food in intestines.Therefore,the results suggest that agrp1 might be involved in the regulation of circadian feeding rhythm in C.carpio rubrofuscus.However,there was no correlation between expression level of agrp2 and feeding rhythm.It is indicated that agrp2 might have different functions in the evolutionary process.