Faculty of Agriculture, Princess of Naradhiwas University, Narathiwat, Thailand.
Laboratory of Genetics and Plant Breeding, Graduate School of Horticulture, Chiba University, Matsudo, Chiba, Japan.
PLoS One. 2018 Dec 6;13(12):e0208549. doi: 10.1371/journal.pone.0208549. eCollection 2018.
Jatropha (Jatropha curcas) is an oil-bearing plant used for biodiesel production. Construction of its standard karyotype and identification of the euchromatin/heterochromatin distribution associated with gene expression and meiotic recombination are essential to fully characterize its genome. Here, we developed a J. curcas karyotype based on meiotic pachytene chromosomes. In addition, a karyotype of J. integerrima, a useful species for jatropha breeding, was also constructed. Five out of eleven J. curcas chromosomes were metacentric, but only two were metacentric in J. integerrima. Almost all of the heterochromatin was distributed around the pericentric regions. The interstitial and distal regions were euchromatic without heterochromatic knobs, except for small heterochromatin regions associated with the subtelomeric repeat sequence JcSat1. These pericentric heterochromatin distribution patterns, together with chromosome structure data and the results of FISH probing with rDNA and JcSat1, allowed us to classify all chromosomes of both species. The two species had two 35S rDNA loci and one 5S rDNA locus; one 35S rDNA locus in J. integerrima was located on the interstitial region of the short arms. In addition, JcSat1 was found at only the heterochromatic ends of the J. curcas chromosome, not the J. integerrima chromosome. Despite the same chromosome number, the two pachytene chromosome-based karyotypes suggest variation in chromosome structure and distribution of repetitive DNAs in these two species.
麻疯树（Jatropha curcas）是一种用于生物柴油生产的含油植物。构建其标准核型并鉴定与基因表达和减数分裂重组相关的常染色质/异染色质分布，对于充分表征其基因组至关重要。在这里，我们基于减数分裂粗线期染色体构建了 J. curcas 的核型。此外，还构建了一种有用的麻疯树育种物种 J. integerrima 的核型。在 11 条 J. curcas 染色体中，有 5 条是中部着丝粒染色体，但在 J. integerrima 中只有 2 条是中部着丝粒染色体。几乎所有的异染色质都分布在着丝粒周围。间插和末端区域是常染色质，没有异染色质节，除了与端粒重复序列 JcSat1 相关的小异染色质区域。这些着丝粒异染色质分布模式，加上染色体结构数据和 rDNA 和 JcSat1 的 FISH 探测结果，使我们能够对两个物种的所有染色体进行分类。这两个物种都有两个 35S rDNA 基因座和一个 5S rDNA 基因座；J. integerrima 中的一个 35S rDNA 基因座位于短臂的间插区域。此外，JcSat1 仅存在于 J. curcas 染色体的异染色质末端，而不存在于 J. integerrima 染色体上。尽管染色体数目相同，但基于粗线期染色体的两个核型表明这两个物种的染色体结构和重复 DNA 分布存在差异。
