| The death and lysis of bacterial cell is controlled by the cid AB/lrg AB system, which can regulate the release of murein hydrolase and thus manipulate the fate of bacterial cell. Bacteria Lrg B homologous genes widely exist in plant kingdom, Arabidopsis thaliana At Lrg B gene may have evolved from gene fusion of bacterial lrg A and lrg B, because of the higher homology between its lrg B domain and bacteria lrg B protein, Arabidopsis thaliana Lrg AB was so named At Lrg B. At Lrg B plays an important role in chloroplast development, carbon partitioning and leaf senescence. Solanum lycopersicum is the model plant for research of fruit development and mature, however, research about Sl Lrg B gene is still in a blank state.After bioinformatic analysis of tomato genome, only one Lrg B was found. This study isolated Lrg B homologous gene from tomato, protein structure characteristics was analysed, as well as evolutionary relationships and promoter informations; Furthermore, expression of Sl Lrg B in different organizations, different period of leaves and light、different hormones and adversity response were investigated. To confirm function of Sl Lrg B in vivo, the over-expression vector and under-expression vector of Sl Lrg B were constructed, and successfully obtained the corresponding transgenic plants. Through the phenotypic analysis and quantitative test of related genes, this study preliminary explore the biological function of Sl Lrg B genes in tomato growth and development. The main results are as follows:① Structure analysis found that tomato Sl Lrg B is a transmembrane protein encoding 513 amino acids, containing a chloroplast transit peptide and 10 transmembrane helices.② Lrg B homologous gene is prevalent in plants and bacteria, and amino acid sequence alignment results showed that the Lrg B domain in the C-terminal region of Sl Lrg B was highly conservative in bacteria and plants, the N-terminal region of plant Lrg B also have similarities with prokaryotes Lrg A genes, but the conservative was lower than that observed for the Lrg B domain, the above results showed that the Lrg B and Lrg A genes of bacteria have evolved into two structural domains in tomato Sl Lrg B. Evolutionary relationship analysis showed that tomato Sl Lrg B has high homology with Arabidopsis thaliana At Lrg B and Hordeum vulgare subsp. Vulgare Hv Lrg B.③ Promoter function components analysis found that there were many light response components and methyl jasmonic acid components, gibberellin response component, salicylic acid response components, auxin response components, anaerobic response components, low temperature response components and drought response components. Treated with different light, hormones and adversity found that the expression of Sl Lrg B was highly repressed by dark, Eth, Me JA, temperature(cold and hot) and re-watered after drought, the above results showed that the tomato Sl Lrg B genes may be involved in these stress response pathways.④ By analysing the expression patterns of Sl Lrg B gene in tomato different organizations, the study found that Sl Lrg B only expressed in green organs, and the expression level of leaves is significantly higher than other green tissues. The expression level of Sl Lrg B continuously reduced with the maturation and senescence of leaves.⑤ By observing the morphological characteristics of Sl Lrg B overexpression plants, the study found that Sl Lrg B over-expression plants displayed growth retardation and etiolated phenotypes. In addition, lower chlorophyll content can also be detected in fruit and leaves of Sl Lrg B over-expression plants. Quantitative PCR results showed that over-expression of Sl Lrg B can promote the programmed cell death, on the contrary, programmed cell death were suppressed in the as Sl Lrg B plants, it supposed that Sl Lrg B participated in the regulation of programmed cell death. The pathways of chlorophyll synthesis and degradation were suppressed in either Sl Lrg B-overexpression plants or as Sl Lrg B lines, indicating that Sl Lrg B gene also regulates the synthesis and degradation of chlorophyll. |
PDF Full Text Request