Zuckerkandl E
Institute of Molecular Medical Sciences, Palo Alto, CA 94306.
J Mol Evol. 1994 Dec;39(6):661-78. doi: 10.1007/BF00160412.
Aspects of the regulatory interactions among genes are probably as old as most genes are themselves. Correspondingly, similar predispositions to changes in such interactions must have existed for long evolutionary periods. Features of the structure and the evolution of the system of gene regulation furnish the background necessary for a molecular understanding of parallel evolution. Patently "unrelated" organs, such as the fat body of a fly and the liver of a mammal, can exhibit fractional homology, a fraction expected to become subject to quantitation. This also seems to hold for different organs in the same organism, such as wings and legs of a fly. In informational macromolecules, on the other hand, homology is indeed all or none. In the quite different case of organs, analogy is expected usually to represent attenuated homology. Many instances of putative convergence are likely to turn out to be predominantly parallel evolution, presumably including the case of the vertebrate and cephalopod eyes. Homology in morphological features reflects a similarity in networks of active genes. Similar nexuses of active genes can be established in cells of different embryological origins. Thus, parallel development can be considered a counterpart to parallel evolution. Specific macromolecular interactions leading to the regulation of the c-fos gene are given as an example of a "controller node" defined as a regulatory unit. Quantitative changes in gene control are distinguished from relational changes, and frequent parallelism in quantitative changes is noted in Drosophila enzymes. Evolutionary reversions in quantitative gene expression are also expected. The evolution of relational patterns is attributed to several distinct mechanisms, notably the shuffling of protein domains. The growth of such patterns may in part be brought about by a particular process of compensation for "controller gene diseases," a process that would spontaneously tend to lead to increased regulatory and organismal complexity. Despite the inferred increase in gene interaction complexity, whose course over evolutionary time is unknown, the number of homology groups for the functional and structural protein units designated as domains has probably remained rather constant, even as, in some of its branches, evolution moved toward "higher" organisms. In connection with this process, the question is raised of parallel evolution within the purview of activating and repressing master switches and in regard to the number of levels into which the hierarchies of genic master switches will eventually be resolved.
基因之间调控相互作用的各个方面可能与大多数基因本身一样古老。相应地，在如此漫长的进化时期里，这种相互作用发生变化的相似倾向必定一直存在。基因调控系统的结构特征与进化为从分子层面理解平行进化提供了必要背景。明显“不相关”的器官，比如果蝇的脂肪体和哺乳动物的肝脏，可能呈现出部分同源性，这种部分同源性有望进行量化。这似乎也适用于同一生物体中的不同器官，例如果蝇的翅膀和腿。另一方面，在信息大分子中，同源性确实是全有或全无的。在器官这种截然不同的情况中，类比通常被认为代表着减弱的同源性。许多推测的趋同实例很可能最终被证明主要是平行进化，大概包括脊椎动物和头足类动物眼睛的情况。形态特征的同源性反映了活跃基因网络的相似性。在不同胚胎起源的细胞中可以建立起相似的活跃基因连接。因此，平行发育可被视为平行进化的对应物。导致c - fos基因调控的特定大分子相互作用被作为一个被定义为调控单元的“控制节点”的例子给出。基因控制中的定量变化与关系变化有所不同，并且在果蝇的酶中可以观察到定量变化中频繁出现的平行现象。也预期会出现基因表达定量方面的进化逆转。关系模式的进化归因于几种不同的机制，尤其是蛋白质结构域的重排。这种模式的发展部分可能是由针对“控制基因疾病”的一种特殊补偿过程导致的，这个过程会自发地倾向于导致调控和生物体复杂性的增加。尽管推断基因相互作用的复杂性在增加，但其在进化时间上的进程尚不清楚，即使在进化朝着“高等”生物发展的一些分支中，被指定为结构域的功能和结构蛋白质单元的同源组数量可能仍相当稳定。与此过程相关，人们提出了在激活和抑制主开关的范围内以及关于基因主开关层次最终会分解成的层次数量方面的平行进化问题。
