Williams Elizabeth A, Degnan Sandie M
School of Biological Sciences, The University of Queensland, St Lucia 4072, Brisbane, Qld, Australia.
Mol Ecol. 2009 Nov;18(21):4434-49. doi: 10.1111/j.1365-294X.2009.04371.x. Epub 2009 Sep 28.
The drastic shift from pelagic larvae to benthic adult form that occurs during marine invertebrate metamorphosis is often induced by intimate interactions between settling larvae and their benthic environment. Larval experience prior to and during metamorphosis can significantly affect adult fitness, but it is presently unknown whether the exact nature of the inductive cue is an experience that matters, or by what mechanism such carry-over effects are mediated. Here we test for carry-over effects of the specific nature of inductive cues on gene expression in metamorphosing postlarvae of the tropical abalone, Haliotis asinina. Postlarvae induced by three different species of coralline algae all successfully undergo metamorphosis, yet the expression profiles of 11 of 17 metamorphosis-related genes differ according to which species of algae the larvae settled upon. Significantly, several genes continue to be differentially expressed for at least 40 h after removal of the algae from the postlarvae, clearly demonstrating a carry-over effect of inductive cue on gene expression. We observe a carryover effect in several genes with varying functions and spatial expression patterns, indicating that each algal species impacts global gene expression in a unique manner. These data unexpectedly reveal that transcriptional modulation of metamorphosis-related genes is contingent upon the precise composition of the benthic microenvironment experienced directly at induction of settlement, and highlight transcription as a mechanism that can mediate between larval and postlarval experiences. For new recruits into an abalone population, metamorphosis clearly does not represent a new transcriptional beginning.
海洋无脊椎动物变态过程中从浮游幼虫到底栖成虫形态的剧烈转变，通常是由附着的幼虫与其底栖环境之间的密切相互作用所引发的。变态之前及期间幼虫的经历会显著影响成虫的适应性，但目前尚不清楚诱导线索的确切性质是否是一种重要的经历，以及这种延续效应是通过何种机制介导的。在此，我们测试了诱导线索的特定性质对热带鲍鱼（Haliotis asinina）变态后期幼虫基因表达的延续效应。由三种不同的珊瑚藻诱导的后期幼虫均成功完成变态，然而，17个与变态相关的基因中有11个的表达谱因幼虫附着的藻类种类不同而有所差异。值得注意的是，从后期幼虫中移除藻类后，有几个基因在至少40小时内仍存在差异表达，这清楚地证明了诱导线索对基因表达的延续效应。我们在几个具有不同功能和空间表达模式的基因中观察到了延续效应，表明每种藻类以独特的方式影响整体基因表达。这些数据意外地揭示，与变态相关基因的转录调控取决于附着诱导时直接经历的底栖微环境的精确组成，并突出了转录作为一种可在幼虫和后期幼虫经历之间起介导作用的机制。对于新加入鲍鱼种群的个体而言，变态显然并不代表一个新的转录起点。
