Nikita retrotransposon movements in callus cultures of barley (Hordeum vulgare L.)

Retrotransposons are dynamic elements of the genome and exist in high percentages in the genome of many organisms. However, the majority of retrotransposons are inactivated during development by different mechanisms such as methylation. Some stress conditions may have a stimulating effect on the activation of retrotransposons. In vitro culture conditions can be considered as one of these stress factors due to nutrients, chemicals, physical factors and photoperiods. In this study, Nikita retrotransposon polymorphism was investigated on different calli ages (30-, 60- and 90-day-old) of barley, which developed from the same embryo on MS medium supplemented with 3 mg/L 2,4-D. Mature barley embryos (Hordeum vulgare L. cv. Zafer-160) were cultured for callus formation and sub-cultured every 30 days. Three experiment sets were constructed to determine the polymorphism between individual calli originated from different embryos in the same culture time. Polymorphism was detected using Inter-Retrotransposon Amplified Polymorphism (IRAP) technique with two different Nikita specific forward primers. Three mature embryos were used as control. In total, 20 homomorphic PCR bands were obtained from both reactions in intact embryos. However, some polymorphic bands (similar to 550 and 650 bp) were solely observed in calli. Our results showed that tissue culture conditions caused the movement of Nikita retrotransposon at different ages of calli that originated from the same embryo and at the same time. We explained that all individuals did not show the same effect. To our knowledge, this is the first report on the employment of Nikita based IRAP application in barley in terms of callus development.