Department of Biology, Indiana University, Bloomington, Indiana 47405.
Department of Biology, Indiana University, Bloomington, Indiana 47405
G3 (Bethesda). 2017 Jul 5;7(7):2151-2159. doi: 10.1534/g3.117.041673.
Recognition and rejection of heterospecific male gametes occurs in a broad range of taxa, although the complexity of mechanisms underlying these components of postmating cryptic female choice is poorly understood. In plants, the arena for postmating interactions is the female reproductive tract (pistil), within which heterospecific pollen tube growth can be arrested via active molecular recognition and rejection. Unilateral incompatibility (UI) is one such postmating barrier in which pollen arrest occurs in only one direction of an interspecific cross. We investigated the genetic basis of pistil-side UI between species, with the specific goal of understanding the role and magnitude of epistasis between UI QTL. Using heterospecific introgression lines (ILs) between and , we assessed the individual and pairwise effects of three chromosomal regions (, , and ) previously associated with interspecific UI among species. Specifically, we generated double introgression ('pyramided') genotypes that combined with each of and , and assessed the strength of UI pollen rejection in the pyramided lines, compared to single introgression genotypes. We found that none of the three QTL individually showed UI rejection phenotypes, but lines combining and showed significant pistil-side pollen rejection. Furthermore, double ILs (DILs) that combined different chromosomal regions overlapping differed significantly in their rate of UI, consistent with at least two genetic factors on chromosome three contributing quantitatively to interspecific pollen rejection. Together, our data indicate that loci on both chromosomes 3 and 12 are jointly required for the expression of UI between and , suggesting that coordinated molecular interactions among a relatively few loci underlie the expression of this postmating prezygotic barrier. In addition, in conjunction with previous data, at least one of these loci appears to also contribute to conspecific self-incompatibility (SI), consistent with a partially shared genetic basis between inter- and intraspecific mechanisms of postmating prezygotic female choice.
在广泛的分类群中，都会发生同种异体雄配子的识别和排斥，尽管对这些交配后隐蔽雌性选择成分背后的机制的复杂性了解甚少。在植物中，交配后相互作用的场所是雌性生殖器官（雌蕊），在这个器官内，异源花粉管的生长可以通过主动的分子识别和排斥来阻止。单向不亲和性（UI）就是这样一种交配后障碍，其中只有在种间杂交的一个方向上才会发生花粉阻滞。我们研究了种间 和 之间雌蕊侧 UI 的遗传基础，具体目标是了解 UI QTL 之间的上位性的作用和大小。使用 和 之间的异源渐渗系（IL），我们评估了先前与 种间 UI 相关的三个染色体区域（ 、 和 ）的个体和成对效应。具体来说，我们生成了结合了 和 中的每一个的双渐渗（“金字塔”）基因型，并在金字塔系中评估了 UI 花粉排斥的强度，与单渐渗基因型相比。我们发现，这三个 QTL 中没有一个单独表现出 UI 排斥表型，但结合了 和 的线表现出明显的雌蕊侧花粉排斥。此外，结合了重叠 的不同染色体区域的双 IL（DIL）在 UI 率上有显著差异，这与三个染色体上至少有两个遗传因素对种间花粉排斥有定量贡献一致。总的来说，我们的数据表明，染色体 3 和 12 上的基因座都共同需要 和 之间的 UI 表达，这表明相对较少的几个基因座之间的协调分子相互作用是表达这种交配前合子前屏障的基础。此外，结合以前的数据，这些基因座中的至少一个似乎也有助于同种自交不亲和性（SI），这与交配后合子前雌性选择的种间和种内机制之间存在部分共同遗传基础一致。
