Mazer Susan J, Gorchov David L
Department of Biological Sciences, University of California, Santa Barbara, California, 93106.
Department of Botany, Miami University, Oxford, Ohio, 45056.
Evolution. 1996 Feb;50(1):44-53. doi: 10.1111/j.1558-5646.1996.tb04471.x.
The experimental measurement of additive genetic variation in plant populations is complicated by the potential for non-Mendelian inheritance. Maternal influences on progeny phenotype resulting from the cytoplasmic inheritance of plastids or RNA transcripts and effects of the maternal environment have consequently been the focus of much research. To exclude or to control for these sources of variation, breeding designs (e.g., cross-factored, nested, or diallel) in which genetically unrelated pollen donors are mated to maternal genotypes have been adopted. Using these designs, some empirical studies have detected statistically significant differences among pollen donors in the mean performance of their pollen (the mature male gametophytes) or in the mean phenotype of their progeny. These statistical effects of pollen-donor identity on pollen performance or progeny phenotype have frequently been interpreted as evidence for additive genetic variance among pollen donors, although patrilineal cytoplasmic inheritance or effects of the paternal environment on pollen performance or gene expression are recognized as alternative explanations. We note that environment-specific selection among developing gametophytes-in which the environment experienced by developing pollen grains (or ovules) provides a selective force causing the differential survival of gametophyte genotypes (analagous to meiotic drive)-is an additional process that may cause genetically based paternal (or maternal) effects on gametophyte performance. If genes selected during this process are expressed in the sporophyte (postfertilization), this process could also influence the phenotype of the diploid progeny. Here, we review the potential causes of statistically significant differences in mean phenotype among the gametophytes or progeny of maternal (seed-bearing) or paternal (pollen-donating) parental plants. We suggest an experimental approach that permits the detection or elimination of selection among developing gametophytes as one such cause. Specifically, the replication of homozygous parental genotypes within and across environments allows the detection and measurement of paternal and maternal environmentally induced effects on gametophyte or offspring phenotype, while eliminating meiotic drive as a source of the phenotypic variation.
植物种群中加性遗传变异的实验测量因非孟德尔遗传的可能性而变得复杂。质体或RNA转录本的细胞质遗传以及母体环境对后代表型的影响因此成为众多研究的焦点。为了排除或控制这些变异来源，人们采用了一些育种设计（例如交叉因子设计、嵌套设计或双列杂交设计），即将遗传上不相关的花粉供体与母体基因型进行交配。利用这些设计，一些实证研究在花粉供体花粉的平均表现（成熟雄配子体）或其后代的平均表型中检测到了统计学上的显著差异。花粉供体身份对花粉表现或后代表型的这些统计效应常常被解释为花粉供体之间存在加性遗传方差的证据，尽管父系细胞质遗传或父本环境对花粉表现或基因表达的影响也被认为是其他解释。我们注意到，发育中的配子体之间的环境特异性选择——即发育中的花粉粒（或胚珠）所经历的环境提供一种选择力，导致配子体基因型的差异存活（类似于减数分裂驱动）——是另一个可能导致基于基因的父本（或母本）对配子体表现产生影响的过程。如果在此过程中选择的基因在孢子体中（受精后）表达，这个过程也可能影响二倍体后代的表型。在这里，我们回顾了母本（产种子的）或父本（提供花粉的）亲本植物的配子体或后代之间平均表型存在统计学显著差异的潜在原因。我们提出一种实验方法，该方法能够检测或消除发育中的配子体之间的选择作为一个此类原因。具体而言，在不同环境中对纯合亲本基因型进行复制，能够检测和测量父本和母本环境诱导对配子体或后代表型的影响，同时消除减数分裂驱动作为表型变异的一个来源。
