We recently described lasting changes in the cardiac proteome of American alligators (Alligator mississippiensis) reared under hypoxic conditions, that resemble what embryos encounter in natural nests. While these changes were consistent with functional differences in cardiac performance induced by developmental hypoxia, the magnitude of this response was dwarfed by a much greater effect of development alone (76% of the total differentially abundant proteins). This means that substantial differences in relative steady-state protein expression occur in the hearts of alligators as they mature from egg-bound embryos to 2-year-old juveniles, and this developmental program is largely resistant to variation in nest conditions. We therefore performed functional enrichment analysis of the 412 DA proteins that were altered by development but not hypoxia, to gain insight into the mechanisms of cardiac maturation in this ectotherm. We found that the cardiac proteome of alligators at 90% of embryonic development retained a considerable capacity for transcription and translation, suggesting the heart was still primarily invested in growth even as the animal approached hatching. By contrast, the cardiac proteome of 2-year-old juveniles was weighted towards structural and energetic processes typical of a working heart. We discuss our results in the context of differences in cardiac development between ectothermic and endothermic oviparous vertebrates, and argue that the robust developmental program of the alligator heart reflects a slow-paced ontogeny, unburdened by the requirement to support the elevated peripheral oxygen demand typical of endothermic animals from a young age.

中文翻译：

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成长中的鳄鱼：卵生爬行动物美洲短吻鳄（密西西比鳄鱼）心脏成熟的蛋白质组学观点

我们最近描述了在缺氧条件下饲养的美洲短吻鳄 (Alligator Mississippiensis) 心脏蛋白质组的持久变化，类似于胚胎在天然巢中遇到的情况。虽然这些变化与发育性缺氧引起的心脏功能的功能差异一致，但这种反应的幅度与单独发育的更大影响相形见绌（占总差异丰度蛋白质的 76%）。这意味着，当鳄鱼从受卵胚胎发育成 2 岁的幼体时，它们的心脏中相对稳态蛋白质表达存在显着差异，而且这种发育程序在很大程度上抵抗巢穴条件的变化。因此，我们对 412 种 DA 蛋白进行了功能富集分析，这些蛋白因发育而不是缺氧而改变，深入了解这种变温期心脏成熟的机制。我们发现，在胚胎发育 90% 时，鳄鱼的心脏蛋白质组保留了相当大的转录和翻译能力，这表明即使在动物接近孵化时，心脏仍然主要投资于生长。相比之下，2 岁幼鱼的心脏蛋白质组更侧重于工作心脏典型的结构和能量过程。我们在变温和吸热卵生脊椎动物心脏发育差异的背景下讨论了我们的结果，并认为鳄鱼心脏的稳健发育程序反映了慢节奏的个体发育，不受支持典型的外周氧需求升高的要求的负担。从小就喜欢吸热的动物。