Genome. 1996 Feb;39(1):77-82. doi: 10.1139/g96-011.
Lycopersicon esculentum (tomato) has a small genome (2C = 1.90 pg of DNA) packaged in 2n = 2x = 24 small acrocentric to metacentric chromosomes. Like the chromosomes of other members of the family Solanaceae, tomato chromosomes have pericentromeric heterochromatin. To determine the fraction of the tomato genome found in euchromatin versus heterochromatin, we stained pachytene chromosomes from primary microsporocytes with Feulgen and analyzed them by densitometry and image analysis. In association with previously published synaptonemal complex karyotype data for tomato, our results indicate that 77% of the tomato microsporocyte genome is located in heterochromatin and 23% is found in euchromatin. If heterochromatin is assumed to contain few active genes, then the functional genes of the tomato must be concentrated in an effective genome of only 0.22 pg of DNA (1C = 0.95 pg x 0.23 = 0.22 pg). The physical segregation of euchromatin and heterochromatin in tomato chromosomes coupled with the small effective genome size suggests that tomato may be a more useful subject for chromosome walking and gene mapping studies than would be predicted based on its genome size alone. Key words : tomato, Lycopersicon esculentum, genome size, heterochromatin, euchromatin, pachytene chromosomes, synaptonemal complex.
番茄（西红柿）具有小基因组（2C = 1.90pg 的 DNA），其 2n = 2x = 24 条小近端着丝粒到中间着丝粒染色体被包装在一起。与茄科其他成员的染色体一样，番茄染色体具有着丝粒异染色质。为了确定番茄基因组中存在于常染色质和异染色质中的部分，我们使用 Feulgen 对来自初级小孢子母细胞的粗线期染色体进行染色，并通过密度测定法和图像分析进行分析。结合之前发表的番茄联会复合体核型数据，我们的结果表明，番茄小孢子母细胞基因组的 77％位于异染色质中，23％位于常染色质中。如果假设异染色质中包含很少的活性基因，那么番茄的功能基因必须集中在仅有 0.22pgDNA 的有效基因组中（1C = 0.95pgx0.23=0.22pg）。番茄染色体中常染色质和异染色质的物理分离以及有效基因组的小尺寸表明，番茄可能比仅根据其基因组大小预测的更适合用于染色体步行和基因图谱研究。关键词：番茄，Lycopersicon esculentum，基因组大小，异染色质，常染色质，粗线期染色体，联会复合体。
