Unveiling the chromosome pairing in Saccharum

• Grant number: 23/16470-8
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date until: March 01, 2024
• End date until: February 28, 2026
• Field of knowledge: Biological Sciences - Genetics
• Principal Investigator: Maria Lúcia Carneiro Vieira
• Grantee: Nina Reis Soares
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil

Abstract

The sugarcane (Saccharum spp.) genome is one of the most complex. Modern varieties are highly polyploid and aneuploid as a result of hybridization between Saccharum officinarum and S. spontaneum. Few studies have been carried out on meiotic control in polyploid species, with the exception of the Ph1 locus that harbors the ZIP4 gene (TaZIP4-B2), whose function is to promote homologous pairing and suppress crossover between homeologs. In sugarcane, despite its interspecific origin, bivalent association is favored, and multivalents, if they occur, are resolved at the end of prophase I. In sugarcane, the ZIP4 gene is expressed more abundantly in flowers. ZIP4 expression is higher in S. spontaneum, a neo-autopolyploid, and with lower expression in S. officinarum, a stable octoploid species, the only one that completes the synapse according to the immunolocalization of synaptonemal complex proteins. Using chromosome-specific oligoprobes, we hope to decipher the pairing in sugarcane, both in the parental species and in the modern cultivar SP80-3280. In the parental species, it will be identified whether the observed bivalents are formed by homologous groups, the origin of the univalents and whether the formation of multivalents occurs during pachytene. In the cultivar, it will be investigated whether the bivalents are composed of homologous chromosomes or whether there is a homeologous pairing, and we will additionally investigate how the recombinant chromosomes pair. The results obtained will be of great importance in the development of genomics-assisted breeding approaches in sugarcane, whose complexity, due to high polyploidy and interspecific origin, makes it difficult to define models for the construction of linkage maps and the consequent mapping quantitative loci. (AU)