The Identification Of The Citrus Specific Genes And Their Origin Pattern Analysis

Citrus includes more than dozens species, sweet orange(Citrus sinensis) is one of the most important cultivated species. As the accomplishment of the draft of the sweet orange genome, more and more citrus genomes are sequencing, such as C.clemetina, Severinia buxifolia, C.medica, C. ichangenisis and Citrus maxima. These vast databases will make a huge contribution to the study of the comparative genomics analysis, functional comparative genomics and the evolution genomics. The study of the origin and evolution of the Citrus specific genes in the sibling species will give us a hand to reveal the molecular mechanisms the phenotype difference and the different adaptability. With some specific genes identified, it is possible to establish the linkage between the specific characters and the specific genes. In order to use these databases to study the most interesting and the most specific characters in the Citrus,this research aimed at the origin of the specific genes in the sweet orange. Our work included three main parts: The identification and the feature analysis of the specific genes in the sweet orange; The study of the origin of the Citrus specific genes; The research of the origin of the Citrus specific mi RNA. The main results are as follows:(1) The identification and the feature analysis of the specific genes in the sweet orange. By analysing 41 plant species whose genomes have been sequenced and the published EST database, 296 CCSG and 1039 CSG are identified in the sweet orange genome through the comparative genomics analysis. Unlike the CEC, the specific genes have the unique features, such as short sequence, less exons, high GC content, few supporting transcripts, and few functional annotations.(2) The study of the origin of the Citrus specific genes. The molecular mechanisms of the origin of the new genes are mainly summarized as GD, EDS, TE, and so on. Taking these molecular mechanisms as a reference, we analysis the origin of the Citrus specific genes. There are 45 CCSG and 162 CSG in the 102 LSG where the comparative genomics analysis was conducted, we infer that GD might be the origin mechanisms of those 45 CCSG and 162 CSG. Besides; Our results also indicate that 71 CCSG and 119 CSG are involved in the TE; Similarly, one CCSG and eight CSG experienced EDS event.(3) The research of the origin of the Citrus specific mi RNA. Based on the 38 Citrus specific mi RNA families, we analysis the expansion model of the Citrus specific mi RNA. Thirteen Citrus specific mi RNA families have TD event, while ten Citrus specific mi RNA families showed LSD event.