Uneven distribution of expressed sequence tag loci on maize pachytene chromosomes
Uneven distribution of expressed sequence tag loci on maize pachytene chromosomes
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DOI：
10.1101/gr4249906
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发表时间：
2006-01-01
期刊：
影响因子：
7
通讯作者：
Gaut, BS
中科院分区：
文献类型：
--
作者：
Anderson, LK;Lai, A;Gaut, BS
在全基因组范围内研究DNA序列、减数分裂重组以及染色体结构之间的关系一直很困难，因为只有少数标记能将遗传连锁图谱与物理图谱联系起来。在此，我们利用一种新开发的资源——RN - cM图谱，将1195个基因定位的表达序列标签（EST）标记定位到玉米的10条粗线期染色体上。RN - cM图谱描绘了沿着联会复合体（SCs，粗线期染色体）以重组结（RNs）形式存在的交换分布，并能将遗传厘摩（cM）距离转换为染色体上的物理微米距离。进行这种转换后，研究中使用的大多数EST标记位于染色体远端的常染色质区域。即使只考虑常染色质染色体片段，EST在染色体上也明显成簇分布。基因密度和重组率（分别通过EST和RN频率测量）密切相关。然而，端粒区间的交换频率比根据其EST频率所预期的要高得多。对于粗线期染色体，常染色质中的EST密度比异染色质高约4倍，而异染色质中的DNA密度比常染色质高1.4倍。根据DNA密度值以及粗线期染色体中常染色质所占的长度比例，我们估计玉米基因组中约有1500 Mbp处于常染色质区域。这种对玉米基因组结构的概述将有助于研究植物的基因组和染色体进化。
Examining the relationships among DNA sequence, meiotic recombination, and chromosome structure at a genome-wide scale has been difficult because only a few markers connect genetic linkage maps with physical maps. Here, we have positioned 1195 genetically mapped expressed sequence tag (EST) markers onto the 10 pachytene chromosomes of maize by using a newly developed resource, the RN-cM map. The RN-cM map charts the distribution of crossing over ill the form of recombination nodules (RNs) along synaptonemal complexes (SCs, pachytene chromosomes) and allows genetic cM distances to be converted into physical micrometer distances on chromosomes. When this conversion is made, most of the EST markers Used in the study are located distally oil the chromosomes ill euchromatin. ESTs are significantly clustered on chromosomes, even when only euchromatic chromosomal segments are considered. Gene density and recombination rate (as measured by EST and RN frequencies, respectively) are strongly correlated. However, crossover frequencies for telomeric intervals are much higher than was expected from their EST frequencies. For pachytene chromosomes, EST density is about fourfold higher in euchromatin compared with heterochromatin, while DNA density is 1.4 times higher in heterochromatin than ill euchcromatin. Based oil DNA density values and the fraction of pachytene chromosome length that is euchromatic, we estimate that similar to 1500 Mbp of the maize genome is in euchromatin. This overview of the organization of the maize genome will be useful in examining genome and chromosome evolution in plants.