水稻抗稻瘟病、绿叶蝉和黄萎病基因BAC克隆的物理定位

植物单拷贝短序列的染色体原位杂交的检出率一直很低．水稻ＢＡＣ克隆作为一种大容量载体的基因组克隆因其独特的优点已被应用于水稻基因组研究．用生物素标记了两个水稻ＢＡＣ克隆，这两个克隆分别含与抗稻瘟病基因Ｐｉ－５（ｔ）、抗稻绿叶蝉基因Ｇｌｈ和抗稻黄萎病基因ＲＴＳＶ在连锁图中等位的ｃＤＮＡ标记ＲＺ５６５和ＲＺ２６２，并用其进行了水稻染色体原位杂交．它们分别被定位在水稻第四染色体长臂距着丝粒百分距离４０％和短臂１００％处．由于供杂交ＢＡＣ克隆含与３种抗病基因等位的标记，因此这些克隆的位置也就是供测抗病基因的位置．杂交检出率由迄今沿用的质粒克隆探针杂交的１０％以下提高到了４６．８％和５９．２％．检出染色体的号数与遗传图确定的染色体相符，证实了用ＢＡＣ克隆进行染色体原位杂交的优越性，为广泛利用水稻ＢＡＣ克隆进行单拷贝小片段基因的定位打下了基础．

PHYSICAL LOCATION OF THE RICE Pi 5(t),Glh AND RTSV LOCI BY ISH OF BAC CLONES

Mapping of low or single copy sequences on plant chromosomes has proven difficult because of very low frequency of signal detection. Rice BAC library is being used widely in rice genome research due to its distinctive advantages over other library systems. In this study, two biotin labeled rice BAC clones closely linked to a rice blast resistance, green leafhopper resistance and tungro spherical virus resistance loci, Pi 5(t),Glh, RTSV, were in situ hybridized to rice chromosomes. They were located on the long arm and short arm of chromosome 4 with FL value of 40% and 100% respectively. The frequency of signal detection reached 46.8% and 59.2%. The signal location were consistent with the selective marker on rice saturated molecular map. The results demonstrated the advantages to locate BAC clones to chromosomes by in situ hybridization and will facilitate the rice low or single copy gene location by using the BAC library.