Dicer mutants and rdr6 mutant are impaired in an intergenerational increase in homologous recombination frequency in response to the infection with oilseed rape mosaic virus

Abstract

Previous reports demonstrated that viral infection of Arabidopsis and tobacco plants resulted in a local and systemic increase in the homologous recombination frequency (HRF). Furthermore, the progeny of infected plants also exhibited a higher spontaneous frequency of recombination. Arabidopsis plants are known to produce DNA virus-derived small interfering RNAs (siRNAs) in response to Oilseed rape mosaic virus (ORMV) infection; dcl4 and rdr6 mutants are affected in this process and as a result, in viral suppression. Previous research also showed that siRNA biogenesis mutants had a lower frequency of homologous recombination and some of them were even impaired in the intergenerational response to abiotic stress. Therefore, we hypothesized that an increase in the HRF in response to infection might be impaired in Dicer-like (dcl) mutants, and that they might also be required for intergenerational changes. We infected single mutants, dcl2, dcl3, dcl4, rdr6, a double mutant dcl2 dcl3 and a triple mutant dcl2 dcl3 dcl4 with ORMV and tested the HRF in the systemic leaves of infected plants as well as in the progeny of infected plants. A somatic increase in the HRF was impaired in rdr6 and dcl2 dcl3 mutants, while it was not affected in single mutants. All tested mutants were impaired in the intergenerational increase in the HRF. Thus, different proteins in the RdDM pathway are needed to modulate homologous recombination frequency in response to the oilseed rape mosaic virus infection in somatic tissues and in the progeny.