Díaz Noelia, Ribas Laia, Piferrer Francesc
Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), Barcelona, Spain.
PLoS One. 2014 Oct 23;9(10):e111304. doi: 10.1371/journal.pone.0111304. eCollection 2014.
Food supply is a major factor influencing growth rates in animals. This has important implications for both natural and farmed fish populations, since food restriction may difficult reproduction. However, a study on the effects of food supply on the development of juvenile gonads has never been transcriptionally described in fish.
This study investigated the consequences of growth on gonadal transcriptome of European sea bass in: 1) 4-month-old sexually undifferentiated fish, comparing the gonads of fish with the highest vs. the lowest growth, to explore a possible link between transcriptome and future sex, and 2) testis from 11-month-old juveniles where growth had been manipulated through changes in food supply. The four groups used were: i) sustained fast growth, ii) sustained slow growth, iii) accelerated growth, iv) decelerated growth. The transcriptome of undifferentiated gonads was not drastically affected by initial natural differences in growth. Further, changes in the expression of genes associated with protein turnover were seen, favoring catabolism in slow-growing fish and anabolism in fast-growing fish. Moreover, while fast-growing fish took energy from glucose, as deduced from the pathways affected and the analysis of protein-protein interactions examined, in slow-growing fish lipid metabolism and gluconeogenesis was favored. Interestingly, the highest transcriptomic differences were found when forcing initially fast-growing fish to decelerate their growth, while accelerating growth of initially slow-growing fish resulted in full transcriptomic convergence with sustained fast-growing fish.
Food availability during sex differentiation shapes the juvenile testis transcriptome, as evidenced by adaptations to different energy balances. Remarkably, this occurs in absence of major histological changes in the testis. Thus, fish are able to recover transcriptionally their testes if they are provided with enough food supply during sex differentiation; however, an initial fast growth does not represent any advantage in terms of transcriptional fitness if later food becomes scarce.
食物供应是影响动物生长速度的主要因素。这对野生和养殖鱼类种群都具有重要意义，因为食物限制可能会影响繁殖。然而，关于食物供应对幼鱼性腺发育影响的研究，尚未有在转录水平上对鱼类进行描述的报道。
本研究调查了生长对欧洲海鲈性腺转录组的影响，具体如下：1）对4月龄性未分化的鱼类，比较生长最快和最慢的鱼的性腺，以探索转录组与未来性别的可能联系；2）对11月龄幼鱼的睾丸进行研究，通过改变食物供应来控制生长。使用的四组分别为：i）持续快速生长组，ii）持续缓慢生长组，iii）加速生长组，iv）减速生长组。性未分化性腺的转录组并未受到初始生长自然差异的显著影响。此外，还观察到与蛋白质周转相关基因表达的变化，慢生长鱼中分解代谢占优，而快生长鱼中合成代谢占优。而且，从受影响的代谢途径以及蛋白质 - 蛋白质相互作用分析推断，快生长鱼从葡萄糖获取能量，而慢生长鱼则有利于脂质代谢和糖异生。有趣的是，当迫使最初快速生长的鱼减速生长时，发现了最大的转录组差异，而加速最初缓慢生长鱼的生长则导致转录组与持续快速生长鱼完全趋同。
性别分化期间的食物可利用性塑造了幼鱼睾丸转录组，不同能量平衡下的适应性变化即为证据。值得注意的是，这一过程发生时睾丸并无明显的组织学变化。因此，如果在性别分化期间为鱼类提供充足的食物供应，它们能够在转录水平上恢复其睾丸；然而，如果后期食物变得稀缺，初始的快速生长在转录适应性方面并不具有任何优势。
