玉米S型CMS线粒体DNA中R区转录的组织特异性

Tissue Transcription Specificity of R Region in Mitochondrial DNA of S-type CMS Maize

玉米S型CMS为配子体雄性不育类型 ,其线粒体DNA上的R区被证明与胞质育性密切相关。R区含有orf35 5和orf77两个开放阅读框 ,被认为是玉米S CMS重要的胞质育性候选基因。本研究通过对一组同质异核的S型CMS材料R区转录产物的Northern分析和RT PCR检测 ,揭示了线粒体DNA中R区的双链转录模式及其中orf35 5 orf77mRNA链转录长度的组织特异性 ,并发现核基因rf3和Rf3特异性地导致雄配子中R区转录或加工情形的变化 ,而对黄化苗和单核花粉期叶片中R区的转录无影响。R区的这种转录模式及调控机制可能是玉米S CMS的重要成因。

S type CMS in maize is gametophyte male sterility different from other CMS types in maize and it is proved that the recombination region R in the mitochondria DNA is tightly associated with cytoplasmic sterility phenotype. Two open reading frames-orf355 and orf77 in R region is regarded as candidate cytoplasmic gene for CMS. Northern and RT-PCR analysis in this research demonstrated a double-strand-transcribing-model of R region and its tissue transcription specificity. In addition, nuclear sterile gene rf3 and nuclear fertile restore gene Rf3 were found to lead typically to the changes of the method of transcription or post-transcription process of R region in tassel, but not in etiolated shoot or leaf in the stage of monocaryon-pollen. The transcribing model of R region and the regulation mechanism for the transcription of R region maybe the causes of S type CMS in maize.