Department of Biology, Faculty of Science, Chiba University, Yayoi, Inage, Chiba 263-8522, Japan;
Am J Bot. 2004 Jan;91(1):65-72. doi: 10.3732/ajb.91.1.65.
Pinus species have three differently inherited genomes: paternal chloroplast, maternal mitochondrial, and biparental nuclear. Our previous study on the hybrid zones between alpine Pinus pumila and montane to subalpine P. parviflora var. pentaphylla demonstrated contrasting patterns of introgression of two cytoplasmic genomes, i.e., the paternal cpDNA flowed from P. parviflora var. pentaphylla to P. pumila, and the maternal mtDNA flowed in the reverse direction. In the present study, we developed codominant nuclear DNA markers diagnostic or mostly diagnostic for each parental species by single-strand conformation polymorphism (SSCP) of polymerase chain reaction (PCR) products, using expressed sequence tag (EST) primers of Pinus taeda. To describe the introgressive patterns of the nuclear genes, the molecular hybrid index (MHI) showing the overall proportion of alleles inferred to be derived from P. pumila was determined for each plant collected in hybrid zones on Mt. Asahidake and Mt. Higashiazuma, Japan. At Mt. Asahidake, the MHI values changed clinally according to the altitudes at which the plants were collected. However, at Mt. Higashiazuma, there was a gap in the MHI values between the plants above and below the Abies and Tsuga forest zone (alt. 1800-1900 m). This suggested that the zone plays a role in creating an effective barrier to gene flow in the hybrid zone.
父本叶绿体、母本线粒体和双亲核基因组。我们之前对高山松和亚高山至低山的华山松变种五针松杂交区的研究表明，两种细胞质基因组的基因渗入存在相反的模式，即父本 cpDNA 从华山松变种五针松流向高山松，而母本 mtDNA 则流向相反的方向。在本研究中，我们利用火炬松的表达序列标签（EST）引物，通过聚合酶链反应（PCR）产物的单链构象多态性（SSCP），开发了每个亲本种的共显性核 DNA 标记，这些标记对每个亲本种具有诊断或大部分诊断能力。为了描述核基因的渗入模式，我们对在日本旭岳和东藻琴山的杂交区采集的每株植物，用分子杂种指数（MHI）来确定其来自高山松的等位基因的总体比例。在旭岳，MHI 值根据植物采集的海拔高度呈明显的梯度变化。然而，在东藻琴山，在海拔 1800-1900 米的冷杉和云杉林带以上和以下的植物之间，MHI 值存在一个缺口。这表明该带在杂交区的基因流中起到了有效的屏障作用。
