摘要
玉米S组细胞质雄性不育（CMS）可能与线粒体基因组中的R区域有关。对不同核背景下唐徐、双2种S胞质的线粒体DNA以R区特异探针的Southern分析发现均有6.7kb、4.5kb、1.8kb的3条谱带，分别对应于2种位于线粒体基因组中间的类型和1个线性末端，并且核背景对这3种不同形式的R区域的量有影响。对Mo17和77核背景下N、T、C_4种胞质17种材料的玉米线粒体基因组中R区的Southern分析发现在C组CMS中不存在R序列，T组中可能只存在R的部分片段，N、S组中都存在R区但有长度上的差别。还观察到了在Mo17和77核背景下不同来源的S胞质材料包括从国外引进的如CMS朣、Vg和在国内玉米品种中发现的CMS材料如唐徐等有着相同的R区结构。用R区域特异引物从S胞质材料唐徐、WB中扩增出了R区的1个1kb的片段并进行DNA序列测定，以此DNA片段为探针从Mo17 CMS朖线粒体基因文库中筛选出并亚克隆了6.7kb的完整的BamHI酶切片段。DNA序列分析表明在R区内有2个开放阅读框（orf），其中orf77中有3段序列与玉米线粒体atp9基因的编码区和3′侧翼有同源性。在6.7kb片段的R区上游的DNA序列包括有cox_II基因，这种结构不同于已报道的R区的结构。R区的特点可能与S组的CMS形成机理和育性不稳定性有关。
The S-type CMS of maize was reported to be caused by a DNA region designated R in mitochondrial genomes. Through PCR using artificial primers, 1kb DNA fragments were obtained from mitochondrial DNA of Tangxu and WB cytoplasm.The DNA sequences are almost the same as the sequence in R region of CMS-S. Using the DNA fragment from Tangxu cytoplasm as probe to scan the Mo17 CMS-J gene library, several positive clones appeared. The clone B39 contains a 6.7kb BamHI fragment with R region. Nucleotide sequence analysis found two orfs including the chimeric orf77. Seventeen lines of maize under Mo17 and 77 nuclear background including N, T, C, S four types of cytoplasm were used for RFLP. Three types of R were discovered in S-type CMS, but not in C group. The R in N group was different from that in S group. T group had only part of R region. The Southern blot of Tangx and Shuang cytoplasm in R regions showed different ratio of R in different nuclear backgrounds. The heterogeneity of R region suggests that the organization and rearrangement of R controlled by the nuclear background. R region seems to be involved in the mechanism of S group CMS. Varieties of structures of R, the ratio of three R types, different DNA sequences in R region of different CMS mightbe concerned with instability of S-type CMS.
基金
国家自然科学基金!(39670466)
国家高校博士点基金!(980404)
