Liverwort Oil Body Development And Phylogentics Of Related Genes

The transition of water to land is the major event of plant evolution. The earliest megafossil records in Late Silurian and Devonian were supposed a land flora of liverwort-like plants. It is consistent with the hypothesis that liverwort is the most basal lineage of land plants, resulted from a series of phylogenetic evidences. Thus, liverworts are likely to retain most of the characteristics of land plants ancestors, including morphology and functional genes, which can be applied as idea materials for the study of the origin of land plants.One of the most striking differences between the cells of the vast majority of liverworts and those of all other groups of land plants is the presence of highly refractive structures commonly known as oil bodies. Oil body is an organelle with biological membrane bounding numerous osmiophilic globules in a proteinaceous matrix. The origin of oil body is still in debate. The functions of these bodies are rarely reported possibly because the isolation and purification of intact liverwort oil bodies are difficult. Until now the study on oil body is still on morphological level. As an organelle, it is far behind the studies on chloroplast, mitochondria, and vacuole. It is commonly accepted that the oil body is unique in liverworts, which has no structural equivalent in other plants.In this study, the oil body origin and development were followed during the spore germination of Plagiochila shangaica Steph.. The oil body development was the progress that cytoplasmic lipid droplets were degraded and endocytosed by small vesicles gradually, and finally enclosed in a limiting double membrane structure. This progress was similar to the lipid droplet lysis in haploid pollen tube germination. With further morphologic, development, dynamic behavior comparison on oil body and lipid droplet, the hypothesis that oil body is not unique in liverworts was speculated. Oil body and lipid droplet are two physiological status of the same subcellular structure.Oleosins form a steric barrier surface on lipid droplets in cytoplasm, preventing it from contacting and coalescing with adjacent droplets. We A) detected the Oleosin gene in Marchantia polymorpha L. genome, supported the above hypothesis as well; B) determined the sequence of molecular gene, combining with the molecular cloning results; C) reconstructed Oleosin gene phylogenies based on nucleotide (96DNA sequences) and amino acid (146protein sequences) sequences from29representative species covering almost all the main lineages of land plants; D) distinguished M-oleosins from the two previously known isoforms for the first time, based on gene structure, phylogenetic relationships, tissue expression, and immunological characteristics; E) described the intron insertion rule of the three isoforms, in both of the L-isoform and M-isoform a single intron inserts behind the central domain, while in the H-isoform, a single intron is located at the5’-terminus; and F) correctly classified one Oleosin gene, Coffea canephora_OLE05, which has been classified to the wrong isoforms in previous studies.Bis(bibenzyl)s is almost specific in liverworts, probably as the storage compound of oil bodies. Cytochrome P450(P450s) mediates the intermolecular phenol coupling, the key step of bis(bibenzyl)s biosynthesis. In this study, A)66predicted Marchantia P450s fragments were found in current available M. polymorpha genome, which fell into three single family P450clans (51,74,710clan), and four main multiple-family clans (71,72,85and86clan); B) reconstructed phylogenetic trees of P450s, the oldest51clan, and four multiple gene family clans throughout green plant evolution, involved in thousand genes from six main lineages of plant kingdom, Chlamydomonas reinhardtii P.A. Dang.(green alga), M. polymorpha (liverwort), Physcomitrella patens (Hedw.) Bruch&Schimp.(moss), Selaginella moellendorffii Hieron.(lycopod (fern)), Oryza sativa L.(monocot), and Arabidopsis thaliana (L.) Heynh.(eudicot); C) moved four Chlamydomonas-specific families, CYP737,738, 739and740out of85clan based on phylogenetic analyses; D) confirmed the74clan and all the four main diversified family clans evolved in the process of land colonization and conserved in later evolution; and E) classified24Selaginella-specific families into their phylogenetic belonging families; F) found out a handful of historic problems in P450nomenclatures.The present study deals with the morphological development and related gene phylogenetics of liverwort oil bodies with a series of developmental and phylogenetic evidences supporting the hypothesis that oil bodies are not unique in liverworts. The phylogenetic analyses on P450s suggest that the P450s were playing an important role in territorial habitat adaptation during the plant colonization, involving in the synthesis of sporopollenin, plant organ growth, ultraviolet resistance and chemical defense.