The Cloning And Evolutionary Analysis Of Polyubiquitin Genes In Porphyra Yezoensis

Porphyra is a genus of marine red algae, of which a total of 134 species have been reported from all over the world. Porphyra yezoensis Ueda is a unique species in the western of Pacific Ocean. It is one of the most economically important marine crops which has been predominately cultivated in China, Japan and Korea peninsula. Recently it has been suggested as a model plant in marine biological sciences for basic and applied studies because of its unique dimorphic generation cycle, apparently small genome size and chromosome number, and ease of reproducing a complete life cycle with in a few months in the laboratory culture system.Recently, the research of P. yezoensis has been developing quickly, scholars issued more than 20,000 P. yezoensis expressed sequence tags (ESTs). The expressed sequence tags (ESTs) play an important role in the research of functional genomics. It has already been used in the cloning of new gene and its function annotation of genome and so on. Herein, we cloned two polyubiquitin genes from the nuclear genome DNA through polymerase chain reaction(PCR).Ubiquitin is a highly conserved protein of 76 amino acids, which plays an important role in a broad array of basic cellular processes. It is encoded by two classes of genes comprised of monomeric genes and polyubiquitin genes. Polyubiquitin genes have been found in yeast, plants and animals. The canonical structure of polyubiquitin genes is tandem 228bp repeats of ubiquitin coding unit, generally with no intron present. The two P. yezoensis polyubiquitin genes (named respectively PUBI-1 and PUBI-2) we cloned possess a classic structure of polyubiquitin gene. PUBI-1 has seven ubiquitin units and PUBI-2 has six ubiquitin units. This is different from that of other Rhodophytas polyubiquitin genes investigated, which have only one polyubiquitin gene (composed of six mono-Ubs). The GC content of the two genes is 60%,and the GC content at 3PrdP position of codon reach to 90.1%;They are subjected to concerted evolution which differs from 4 other Florideae polyubiquitin genes. The tolerant roles of polyubiquitin genes have been investigated extensively in yeast and algae. As one of the most economically important marine crops, it is very important to learn the resistant mechanism of P. yezoensis. In the research, we have cloned the polyubiquitin genes of P. yezoensis. It provides much valuable information for studying resistant mechanism and the evolution of polyubiquitin gene in P. yezoensis. .