Format: ORAL

Lopez-Gomollon, Sara

University of Kent, Canterbury, UK

Genomic shock is an umbrella term used to define a situation leading to genome-wide misregulation of the transcriptome and changes in the epigenome, disrupting gene regulation and inducing chromosomal rearrangements and the mobilization of TEs. This effect is usually associated to hybridisation. Genomic shock can be seen as a source of heritable variation, able to trigger extensive phenotypic effects. However, the molecular mechanisms associated are not well understood. Small (s)RNAs can mediate gene silencing at transcriptional or posttranscriptional level. In hybrids, sRNAs from one parent may find new targets in the genome of the other parent, modifying gene expression. We have observed changes to gene expression in interspecific Solanum hybrids associated with small RNAs derived from endogenous pararetroviruses, a type of transposable element. There were prominent changes to sRNA profiles in these hybrids involving 22nt species produced in the DCL2 biogenesis pathway and the hybridisation-induced changes to gene expression were like those in a dcl2 mutant. These findings indicate that hybridisation leads to activation of EPRV, perturbation of small RNA profiles and, consequently, changes in gene expression. Grafting is another potential source of genomic shock as a genome is exposed to the presence of foreign nucleic acids. Using grafting of two tomato genotypes, we study the mobility of small RNAs and the changes induced at genetic and epigenetic level. Such hybridization- or graft- induced variation in gene expression could increase the natural phenotypic variation in natural evolution or in breeding, so a better understanding will benefit crop improvement strategies.