THE GENOME OF ZEA-MAYS, ITS ORGANIZATION AND HOMOLOGY TO RELATED GRASSES
THE GENOME OF ZEA-MAYS, ITS ORGANIZATION AND HOMOLOGY TO RELATED GRASSES
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DOI：
10.1007/bf00327318
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发表时间：
1980-01-01
期刊：
影响因子：
1.6
通讯作者：
WALBOT, V
中科院分区：
文献类型：
--
作者：
HAKE, S;WALBOT, V
分析了玉米的基因组组织模式，并通过DNA：DNA杂交分析了玉米与可能的祖先种的亲缘关系。将玉米DNA的470和1350个碱基对片段重新结合到不同的COT[DNA的初始浓度为每升核苷酸的摩尔。值表明基因组由3个主要的动力学类别组成：高度重复、中等重复和独特。短片段长度重复序列的Mini-cot曲线表明，高度重复序列类占基因组的20%，平均重复频率为80万个拷贝；中等重复序列类为基因组的40%，平均重复频率为1000个拷贝。热变性研究表明，高重复序列有12%的发散，中重复序列有6%的发散。基因组的大部分以两种散布模式组织。一个约占基因组的1/3，由平均长度为2100个碱基的独特序列组成，其间穿插着中等重复序列；另一个，也占基因组的1/3，是穿插着高度重复序列的中等重复序列。经EM测定，重复序列为500-1000bp。基因组的其余三分之一是距离回文或重复序列5000个碱基对以上的独特序列。从中西部登特到爆米花和相关牧草的玉米DNA杂交表明，独特的和重复的序列元件都发生了分化。Teosinte和爆米花与中西部Dent的差异大致相同，而Tripsaum的差异要大得多。从异源双链中熔点的降低计算出的发散时间表明，玉米内部以及玉米与近亲之间的发散至少比预期的大一个数量级。这种高度的分化可能反映了玉米驯化的压力。
The pattern of genome organization of Z. mays was analyzed, and the relationship of maize to possible progenitor species assessed by DNA:DNA hybridization. Reassociation of 470 and 1350 bp [base pair] fragments of maize DNA to various COt [initial concentration of DNA in moles of nucleotides per liter .times. time in seconds] values demonstrates that the genome is composed of 3 major kinetic classes: highly repetitive, mid-repetitive, and unique. Mini-COt curves of the repetitive sequences at short fragment length indicate that the highly repetitive sequence class is 20% of the genome and is present at an average reiteration frequency of 800,000 copies; the mid-repetitive sequence class is 40% of the genome and is present at an average reiteration frequency of 1000 copies. Thermal denaturation studies show that the highly repetitive sequences are 12% divergent and mid-repetitive sequences are 6% divergent. Most of the genome is organized in 2 interspersion patterns. One, approximately 1/3 of the genome, is composed of unique sequences of average length 2100 bp interspersed with mid-repetitive sequences; the other, also 1/3 of the genome, is mid-repetitive sequences interspersed with highly repetitive sequences. The repetitive sequences are 500-1000 bp by EM measurement. The remaining third of the genome is unique sequences farther than 5000 bp from a palindromic or repetitive sequence. Hybridization of maize DNA from Midwestern Dent to popcorn and related grasses indicates that both the unique and repetitive sequence elements have diverged. Teosinte and popcorn are approximately equally divergent from Midwestern Dent whereas Tripsacum is much more divergent. The divergence times calculated from the depression of Tm [melting point] in heterologous duplexes indicate that the divergence within Z. mays and between maize and near relatives is at least an order of magnitude greater than expected. This high degree of divergence may reflect the pressures of domestication of maize.