Wade Michael J, McCauley David E
Department of Biology, Indiana University, Bloomington, Indiana 47405, USA.
Am Nat. 2005 Nov;166(5):592-602. doi: 10.1086/491660. Epub 2005 Aug 30.
Cytoplasmic male sterility (CMS) in plants often results in gynodioecious populations, composed of hermaphrodites and male-sterile females. All models of gynodioecy assume maternal inheritance of the cytoplasmic alleles and postulate a variety of negatively frequency-dependent mechanisms to maintain the cytoplasmic polymorphisms observed in many natural populations. However, in some plant species, mitochondria are transmitted at least occasionally by pollen, a process called paternal leakage. We show that even a small amount of paternal leakage is sufficient to sustain a permanent, stable cytoplasmic polymorphism. Because only hermaphrodites provide pollen in gynodioecious species, the effects of paternal leakage are biased and occur more often from the non-CMS male-fertile haplotype to the CMS male-sterile haplotype. We also show that a nuclear restorer disrupts the polymorphic cytoplasmic equilibrium, leading to fixation of both the CMS allele and the restorer. Although a dominant nuclear restorer fixes, it fixes much more slowly than in the standard CMS models. Although a stable cytonuclear polymorphism is possible with "matching alleles" nuclear restoration, oscillations to low frequencies present a risk of loss by drift. Paternal leakage enhances the stability of joint cytonuclear polymorphism by reducing the chance that a CMS allele is lost by drift.
植物中的细胞质雄性不育（CMS）通常会导致雌全异株种群的形成，该种群由雌雄同株和雄性不育的雌性组成。所有关于雌全异株的模型都假定细胞质等位基因是母系遗传的，并假定存在多种负频率依赖机制来维持在许多自然种群中观察到的细胞质多态性。然而，在一些植物物种中，线粒体至少偶尔会通过花粉进行传递，这一过程称为父系渗漏。我们表明，即使少量的父系渗漏也足以维持一种永久、稳定的细胞质多态性。由于在雌全异株物种中只有雌雄同株提供花粉，父系渗漏的影响是有偏差的，并且更多地发生在从非CMS雄性可育单倍型到CMS雄性不育单倍型的过程中。我们还表明，一个核恢复基因会破坏多态性的细胞质平衡，导致CMS等位基因和恢复基因都固定下来。虽然显性核恢复基因会固定下来，但它的固定速度比标准CMS模型中的要慢得多。虽然通过“匹配等位基因”核恢复可能实现稳定的细胞核-细胞质多态性，但低频振荡存在因漂变而丢失的风险。父系渗漏通过减少CMS等位基因因漂变而丢失的机会，增强了联合细胞核-细胞质多态性的稳定性。
