Experimental fossilization of early plant lipids — tracing incipient terrestrialization using a comparative approach with extant bryophytes and Cambrian-Silurian sediments

藻类到植物的转变以及随之而来的对大陆王国的征服是一个复杂的过程，这是由生物化学途径的进化创新实现的。其中包括萜类化合物和其他次生代谢物的生物合成的变化，这些变化在藻类和植物之间是不同的，这些变化可能已经记录在岩石记录中。追溯早期的陆地化进程，即它的时间、模式和范围对于理解横跨新元古代末期和早期古生代的更大的地球系统变化至关重要。碳埋藏率的提高、海洋氧化还原结构的变化、营养调节的初级生产力和动物的爆炸性辐射都可能受到最早的植物征服陆地的间接影响。利用化石记录追踪最古老的植物是很复杂的，因为在陆地环境中保存得很差，而早期的孢子非常罕见。化石脂质可以提供一个解决方案。然而，迄今为止，最早古生代沉积沉积物中早期分支植物的分子残余物尚未得到足够的重视，这可能部分是因为我们对这些跨越藻类到植物过渡的早期系统发育分支（即蕨、苔类和苔藓类）的分子特征的了解仍然很少。在这里，我提出了一种双重方法，其中将使用热解和催化氢化对上述物种的现代生物量进行“人工老化”，以便更好地了解早期植物的特征生物标志物，同时将系统地研究来自澳大利亚寒武纪和奥陶纪三个陆生影响序列的沉积岩，以找到藻类到植物过渡的任何痕迹。这项研究的结果不仅有可能揭示从藻类到植物的过渡过程中萜类生物合成的进化变化，而且还可能揭示陆地领域的早期殖民，从而对触发因素、促进因素和全球后果施加限制。

The algae-to-plant transition and associated conquest of the continental realm was a complex process, enabled by evolutionary innovation of biochemical pathways. Amongst these are changes in the biosynthesis of terpenoids and other secondary metabolites that differ between algae and plants, and which may have been recorded in the rock record. Tracing the incipient terrestrialization process—i.e. its timing, mode, and extent—is of paramount importance for understanding larger Earth system changes across the terminal Neoproterozoic and early Paleozoic. Enhanced rates of carbon burial, changes in the marine redox structure, nutrient-modulated primary productivity and the explosive radiation of animals may all have been indirectly affected as a consequence of the conquest of land by the earliest plants. Tracing the oldest plants using the fossil record is complicated due to generally poor preservation in terrestrial environments, whilst early spores are exceedingly rare. Fossil lipids can offer a solution. Yet the molecular remnants of early-branching plants in earliest Paleozoic sedimentary deposits have thus far received insufficient attention, which is likely partially due to the fact that our knowledge of molecular signatures of these early phylogenetic branches spanning the algae-to-plant transition (i.e. charophytes, liverworts and bryophytes) is still sparse. Here I propose a dual approach, in which modern biomass of said species will be ‘artificially aged’ using pyrolysis and catalytic hydrogenation in order to obtain a better understanding of characteristic early plant biomarkers, whilst sedimentary rocks from three terrigenous-influenced sequences from Australia, spanning the Cambrian and Ordovician will be systematically studied in order to find any traces of the algae-to-plant transition. The outcomes of this study not only carry the potential to reveal evolutionary changes in terpenoid biosynthesis across the algae-to-plant transition, but may also shed more light on the incipient colonization of the terrestrial realm, thereby placing constraints on triggers, facilitators and global consequences.