Minisymposium 12: Genome evolution

Abs # 25004: Stability of resistance gene loci in the progeny of infected plants

Presenter:	Kovalchuk, Igor , igor.kovalchuk@uleth.ca
Authors	Kovalchuk, Igor  (A)
Affiliations:	(A): University of Lethbridge

Plant response to internal and external stimuli is regulated by a variety of signaling molecules. Recently, our laboratory described a novel finding that local Tobacco mosaic virus inoculation in tobacco triggers a systemic increase in the frequency of somatic intra-chromosomal recombination events in transgenic and endogenous gene loci (Kovalchuk et al., 2003). This finding suggests the existence of cell-non-autonomous systemic recombination signal (SRS) that originates from infected cells and travels to non-infected cells. The signal causes a systemic activation of recombination and results in an increased frequency of progeny plants with genetic changes, suggesting that this phenomenon constitutes an adaptive measure to virus infection. We previously hypothesized that the generation of SRS was a part of plant protection mechanism that could lead to increased frequency of rearrangements in resistance (R) gene loci. Here we show the increased instability of N-gene-like R gene loci in the progeny of the plants that received a SRS. This suggests the existence of systemic mechanisms that force gene shuffling, possibly resulting in the evolution of new resistance genes upon exposure to pathogens. The progeny of infected plants also appeared to tolerate higher concentration of several mutagens (rose Bengal and UVC), suggesting that the other types of adaptation occur in the genome. Another interesting finding was that oxidative stress-generating compounds trigger similar type of signal that results in the higher frequency of recombination in the transgene. It seems that plants possess general stress protection mechanism that involves stress signaling resulting in genome reshuffling as well as in changes of plant sensitivity to stress.