Comparative genomic analysis of the apomixis locus in Paspalum spp.

CALDERINI, O.; MARTÍNEZ, ERIC J.; HOJSGAARD, DIEGO H.; QUARIN, CAMILO L.; PAOLOCCI, F.; CACERES, MARÍA E.; DONNISON, I.; BAUMLEIN, H.; PUPILLI, FULVIO

Rosario, Santa Fe

Congreso; XV Congreso Latinoamericano de Genética. XLI Congreso Argentino de Genética. XLV Congreso de la Sociedad de Genética de Chile. II Reunión Regional SAG-Litoral.; 2012

The opportunity to obtain seeds genetically identical to the mother plant makes apomixis a valuable agronomic trait to be introduced into those crops for which the production of hybrid seed is important. As no genuine apomictic phenotypes has been obtained yet in sexual model species, the natural apomictic species of the genus Paspalum, such as P. simplex, are still interesting models for understanding the genetic control of apomixis in the perspective to introduce it in crop species. The Apomixis Controlling Region (ACR) in P. simplex is partially hemizygous, lacks recombination and, on the basis of its syntenic relationship with a region of the chromosome 12 of rice, spans around 15 cM. A multi-sided strategy is pursued to enable gene discovery at the ACR based on: i) comparative mapping of the ACR in several Paspalum spp. ii) physical dissection of the ACR, iii) differential transcriptomic analysis between apomictic and sexual flowers and iv) functional analysis of candidate genes. These researches have revealed that the ACR is formed by a ?sea? of repetitive/transposable elements in which rare genes are embedded. Most of the genes sequenced so far reveal nonsense and frameshift mutations that turned them into pseudogenes. Although expression of sex related alleles is subjected to a strict time-related regulation, that of their apomixis-linked counterparts appears to be constitutive. Functional analysis of one of the pseudogenes taken as a case study suggests a possible role in apomictc development in P. simplex through silencing of its sexual functional allele.