Experimental hybridization reveals biased inheritance of the internal transcribed spacer of the nuclear ribosomal DNA in Begonia x taipieiensis
Experimental hybridization reveals biased inheritance of the internal transcribed spacer of the nuclear ribosomal DNA in Begonia x taipieiensis
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DOI：
10.1007/pl00013996
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发表时间：
2001-09-01
影响因子：
2.8
通讯作者：
Peng, CI
中科院分区：
文献类型：
--
作者：
Chiang, TY;Hong, KH;Peng, CI
台湾海棠（Begonia x taipeiensis c . i Peng）是台湾海棠与无翅海棠的天然杂交品种。为了了解核糖体DNA在单向杂交中的遗传情况，以台湾双歧杆菌和无翅双歧杆菌分别作为胚珠和花粉供体进行了实验。对人工杂交种、亲本种和天然杂交种的核糖体DNA进行了内部转录间隔区（ITS）扩增。与亲本种ITS的单一类型不同，从天然和人工杂交种中克隆出多个ITS序列。显然，在这种单向杂交中，母系DNA提供了大部分的系统发育信息。在杂交序列中，除了遗传自母本（38.1%）和父本（30.1%）的加性多态性外，还检测到一种新的核苷酸组成（31.8%）。在系统发育推断中，“新”字被视为杂音。它们可能是通过分子内重组获得的，因为没有检测到基因转换。基因重组的发生具有非随机性，在ITS1区（3.14%）和ITS2区（3.42%）的发生频率高于5.8S RNA基因区（2.22%）。考虑到台北白蚁性别重组较少且时间跨度短，不均匀的杂交可能导致了其核基因组ITS组成的异质性。虽然不育杂交种还没有形成独立于亲本物种的谱系，但在这些植物中，高水平的遗传多样性是无性传播并保持的。
Unidirectional hybridization was previously confirmed in Begonia x taipeiensis C.-I Peng, a naturally occurring hybrid resulting from B. formosana x B. aptera, in Taiwan. To understand the inheritance of ribosomal DNA in unidirectional hybridization, experiments were conducted using B. formosana and B. aptera as ovule and pollen donors, respectively. The internal transcribed spacer region (ITS) of nuclear ribosomal DNA was amplified from the artificial hybrids, parental species, and natural hybrids. In contrast to the single type of ITS in the parental species, multiple sequences were cloned from both natural and artificial hybrids. A split decomposition network based on ITS nucleotide variation revealed that all but one (clone B14) of the hybrid sequences were "phylogenetically" closely related to B. formosana. Apparently, in such unidirectional hybridization, maternal DNA provided most of phylogenetic information. In the hybrid sequences, in addition to additive polymorphisms inherited from maternal (38.1%) and paternal (30.1%) plants, a novel nucleotide composition (31.8%) was also detected. The "new" characters are seen as noise in phylogenetic inference. They were probably obtained via intramolecular recombination, as gene conversion was not detected. The occurrence of genetic recombination appeared to be nonrandom, with a higher frequency in the ITS1 (3.14%) and ITS2 (3.42%) regions than in the 5.8S RNA gene (2.22%). Given the lack of sexual recombination in B. X taipeiensis and short time span, unequal crossing-over likely contributed to the heterogeneity of the ITS composition in the nuclear genome. Although the sterile hybrids have not attained their own lineage independent from the parental species, a high level of genetic diversity is transmitted asexually and maintained in these plants.