An environmentally induced adaptive (?) insertion event in flax

Abstract

Genomic changes in flax induced by the environment include the sequences encoding the ribosomal RNAs, many repetitive sequence families and a novel single copy insertion termed LIS-1, comprising a 5.7 kilobase (kb) DNA fragment. The variation in these sequences has been followed in the flax variety Stormont Cirrus under four different growth conditions. LIS-1 was observed to always become both homozygous and inherited in subsequent generations under two of the growth environments. In the third environment, LIS-1 sporadically appeared but was never transmitted to the progeny. Under non-inducing conditions, LIS-1 has been observed neither during growth nor in the next generation. Thus, LIS-1 reached a specific endpoint that depended only on the growth environment. The ribosomal RNA genes also altered during growth under inducing conditions but specific end points that correlated with specific nutrient treatments were not observed. None of these genomic changes were part of the normal developmental processes in flax. In a responsive flax variety that did not produce stable genotrophs, LIS-1 was subsequently lost unless the appropriate inducing conditions were maintained. The results show that the environment can act as both the inducer of targeted genetic variation and as the selective agent for advantageous mutations. Key words: Flax, adaptive variation, insertion events, environmental induction.