Analysis of Genomic Organization, Distribution and Promoter Architecture of Histone Genes in Chlamydomonas reinhardtii

In recent years, Chlamydomonas reinhardtii have gained commercial interest as a system for the production of heterologous proteins with high commercial value. However, the use of this alga for commercial purposes is limited by the inability to obtain strains with an efficient expression of transgenes. The molecular reasons for the low expression of transgenes are not well understood. One of the processes regulated by histones involves the maintenance of a highly coiled chromatin structure that makes DNA less accessible and therefore a poor substrate for active transcription of genes. Therefore, histones are proteins with a strong influence on gene expression as they help to arrange DNA forming a polymer called chromatin. The DNA in the chromatin is organized by two copies of each core histone protein: H2A, H2B, H3, and H4. The aim of this graduation project is generate valuable information that could be used as primary source for future investigations of algal transcriptional regulation. Through reciprocal BLAST, the genes corresponding to the four core histones belonging to Chlamydomonas and other chlorophyte algae were identified. The JBrowse tool of the Phytozome platform was used to visualize and retrieve information about the genomic organization and distribution of each histone gene in Chlamydomonas. For the identification and characterization of histone variants, phylogenetic and protein sequences analyses were performed. We also searched for conserved regions, motifs, in the promoters of each histone gene in Chlamydomonas using the MEME Suite. Our results show that Chlamydomonas contains a greater number of histone genes in comparison with other species of algae and higher plants. Chlamydomonas encodes 125 core histone proteins, including 35 H3, 32 H4, 30 H2A and 28 H2B. From these, seven histone variants were identified. Additionally, we found that the majority of the histone genes are organized in pairs of H3-H4 and H2A-H2B, each one divergently transcribed from a single promoter. The genomic distribution of these groups is not random, they were mainly found as large clusters distributed in few chromosomes. Expression analysis indicates that the synthesis of most histone genes is cell cycle regulated and limited by the S phase. The analysis of the promoter confirm the existence of conserved motifs through most histone genes. A palindromic sequence in the 3’ end was identified, this sequence may be essential for the coordinated expression of histones.

• Huvudupphovsman: Aldaz Villao, María José (author)
• Materialtyp: bachelorThesis
• Språk: eng
• Publicerad: 2019
• Ämnen: Chlamydomonas; Algae; Histone gene; Gene expression; Promoter; Conserved motifs; Alga; Genes de histonas; Variantes; Expresión de genes; Promotor; Regiones conservadas
• Länkar: http://repositorio.yachaytech.edu.ec/handle/123456789/70