Kalisz S, Kramer E M
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Heredity (Edinb). 2008 Feb;100(2):171-7. doi: 10.1038/sj.hdy.6800939. Epub 2007 Jan 31.
The goal of this short review is to consider the interrelated phenomena of phenotypic variation and genetic constraint with respect to plant diversity. The unique aspects of plants, including sessile habit, modular growth and diverse developmental programs expressed at the phytomer level, merit a specific examination of the genetic basis of their phenotypic variation, and how they experience and escape genetic constraint. Numerous QTL studies with wild and domesticated plants reveal that most phenotypic traits are polygenic but vary in the number and effect of the loci contributing, from a few loci of large effects to many with small effects. Further, somatic mutations, developmental plasticity and epigenetic variation, especially gene methylation, can contribute to increases in phenotypic variation. The flip side of these processes, genetic constraint, can similarly be the result of many factors, including pleiotropy, canalization and genetic redundancy. Genetic constraint is not only a mechanism to prevent change, however, it can also serve to direct evolution along certain paths. Ultimately, genetic constraint often comes full circle and is released through events such as hybridization, genome duplication and epigenetic remodeling. We are just beginning to understand how these processes can operate simultaneously during the evolution of ecologically important traits in plants.
这篇简短综述的目的是探讨植物多样性方面表型变异和遗传限制的相关现象。植物的独特之处，包括固着习性、模块化生长以及在叶元水平上表现出的多样发育程序，值得对其表型变异的遗传基础以及它们如何经历和摆脱遗传限制进行专门研究。对野生和驯化植物进行的大量数量性状基因座（QTL）研究表明，大多数表型性状是多基因的，但在起作用的基因座数量和效应方面存在差异，从少数具有大效应的基因座到许多具有小效应的基因座。此外，体细胞突变、发育可塑性和表观遗传变异，尤其是基因甲基化，可导致表型变异增加。这些过程的另一面，即遗传限制，同样可能是多种因素的结果，包括多效性、发育稳态和遗传冗余。然而，遗传限制不仅是防止变化的一种机制，它还可以引导进化沿着某些路径发展。最终，遗传限制常常循环往复，并通过杂交、基因组加倍和表观遗传重塑等事件得以解除。我们才刚刚开始了解这些过程在植物生态重要性状进化过程中是如何同时发挥作用的。
