Evolutionary dynamics and chromosomal distribution of telomeric repeats on chromosomes of Saccharum spp

• Grant number: 14/23828-7
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: January 01, 2015
• End date: September 30, 2015
• Field of knowledge: Biological Sciences - Genetics - Plant Genetics
• Principal Investigator: Marie-Anne Van Sluys
• Grantee: Sárah Gomes de Oliveira
• Supervisor: Andrew R. Leitch
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Queen Mary University of London, England
• Associated to the scholarship: 13/00714-3 - The role of repetitive DNA in the centromeric organization of Saccharum spp, BP.PD

Abstract

The Saccharum complex (Poaceae) is one of the most important species due to its ecological dominance and agricultural and economic importance. Modern sugarcane cultivars are hybrid derivatives from crosses between S. officinarum and S. spontaneum. These cultivars display between 100 and 130 chromosomes, with unequal contributions of the parental genomes. They have large genomes (~10Gb), with a high amount of repetitive DNA, which hinders the development of genetic tools and breeding efforts for this culture. The chromosomes of most eukaryotes are linear, with two ends that comprise the telomeres and the adjacent subtelomeric region. The telomeres are nucleoprotein structures that protect the ends of chromosomes and promote genomic integrity. They are implicated in intra-nuclear chromosome positioning, meiotic chromosome pairing and the regulation of gene expression. In most eukaryotes the structure of telomeres is formed by short G/C-rich tandem repeats, ending with a 32 single-strand overhang. The telomerase uses an integral RNA template to catalyze the addition of telomeric repeats at chromosome ends, compensating the usual shortening of the DNA after cell replication. The TTTAGGG repeat originally characterized in Arabidopsis is considered to be the archetype of plant telomeric sequences, being distributed among the majority of plant species. The exceptions are the alga Chlamydomonas reinhardtii, which has TTTTAGGG repeats, and the Asparagales (group of monocot plants), whose chromosome termini contain vertebrate-type TTAGGG repeats. Telomere binding proteins provide essential functions for chromosome maintenance in most eukaryotes and consequently are well suited for analysis in the context of evolution. As chromatin structures, telomeres undergo epigenetic regulation of their maintenance and function. Analyses of Genomic in situ hybridization (GISH) showed recombination events in sugarcane cultivars, in which the chromosomal recombination indicates a differential parental inheritance at the centromeres and telomeres. A comparative approach in sugarcane cultivars will enable the identification of general features defining the structure, distribution and evolution of telomeric sequences, which in turn will work towards a solution of the end replication problem and, maybe, of more agricultural importance, it will help identify changes associated with parental inheritance. (AU)