Rani V, Singh K P, Shiran B, Nandy S, Goel S, Devarumath R M, Sreenath H L, Raina S N
Laboratory of Cellular and Molecular Cytogenetics, Department of Botany, University of Delhi, Delhi 110 007, India e-mail:
Plant Cell Rep. 2000 Oct;19(10):1013-1020. doi: 10.1007/s002990000228.
The most important commercial species of coffee, Coffea arabica, which produces 73% of the world's coffee crop and almost all of the coffee in Latin America, is the only tetraploid (allotetraploid, 2n=4x=44) species known in the genus. High-frequency somatic embryogenesis, plant regeneration and plant recovery were achieved from leaf explants of a mature, elite plant of C. arabica cv. Cauvery (S-4347) using a two-step culture method. To assess the genetic integrity of the nuclear, mitochondrial and chloroplast genomes among the hardened regenerants, we employed multiple DNA markers (RFLP, RAPD, ISSR) for sampling various regions of the genome. Although the nuclear and mitochondrial genomes of the mother plant and five ramets derived from the mother ortet were similar in organization, this was not so in the somatic embryo-derived plants where both nuclear and mitochondrial genomes changed in different, characteristic ways and produced novel genome organizations. A total of 480 genetic loci, based on the data obtained from a total of 16 nuclear, mitochondrial and chloroplast gene probes, in combination with nine restriction enzyme digests, 38 RAPD and 17 SSR primers, were scored in 27 somatic embryo-derived plants and the single control. Among these, 44 loci were observed to be polymorphic. A relatively low level of polymorphism (4.36%) was found in the nuclear genome, while polymorphism in the mitochondrial genome (41%) was much higher. No polymorphism was detected in the chloroplast genome. The polymorphism in the mitochondrial genome was found in only 4 plants. Such selective polymorphism was not true for the nuclear genome. Thus, this in-depth and comprehensive study demonstrates, for the first time, the presence of subtle genetic variability and novel genome organizations in the commercially well-established somatic embryogenesis-derived plants of this important coffee species.
最重要的商业咖啡品种阿拉伯咖啡（Coffea arabica），产出了全球73%的咖啡作物，并且几乎涵盖了拉丁美洲所有的咖啡，它是该属中已知的唯一四倍体（异源四倍体，2n = 4x = 44）物种。利用两步培养法，从一株成熟的、优良的阿拉伯咖啡品种Cauvery（S - 4347）植株的叶片外植体中实现了高频体细胞胚胎发生、植株再生和植株恢复。为了评估炼苗后的再生植株中核基因组、线粒体基因组和叶绿体基因组的遗传完整性，我们使用了多种DNA标记（RFLP、RAPD、ISSR）对基因组的各个区域进行采样。尽管母本植株及其从母系分株衍生出的五个分株的核基因组和线粒体基因组在组织上相似，但体细胞胚胎衍生植株并非如此，其核基因组和线粒体基因组均以不同的、独特的方式发生了变化，并产生了新的基因组组织。基于从总共16个核基因、线粒体基因和叶绿体基因探针获得的数据，结合9种限制性内切酶消化、38个RAPD引物和17个SSR引物，在27株体细胞胚胎衍生植株和单一对照中对总共480个遗传位点进行了评分。其中，观察到44个位点具有多态性。在核基因组中发现的多态性水平相对较低（4.36%），而线粒体基因组中的多态性（41%）要高得多。在叶绿体基因组中未检测到多态性。线粒体基因组中的多态性仅在4株植物中发现。这种选择性多态性在核基因组中并非如此。因此，这项深入而全面的研究首次证明，在这种重要咖啡品种的商业上成熟的体细胞胚胎发生衍生植株中存在细微的遗传变异性和新的基因组组织。
