Depletion of tyrosyl-DNA phosphodiesterase 1a (MtTdp1a) affects transposon expression in Medicago truncatula

The role of plant tyrosyl-DNA phosphodiesterase 1? in genome stability is studied using a Medicago truncatula MtTdp1?-depleted line. Lack of MtTdp1? results in a 39% reduction of methylated cytosines as compared to control. RNA-Seq analyses revealed that 11 DNA transposons and 22 retrotransposons were differentially expressed in the Tdp1?-2a line. And among them all DNA transposons (MuDR, hAT, DNA3-11_Mad) and seven retrotransposons (LTR/Gipsy, LTR/Copia, LTR and NonLTR/L1) were down-regulated, while remaining 15 retrotransposons were up-regulated. Results suggest that the occurrence of stress-responsive cis-elements as well as changes in the methylation pattern at the LTR promoters might be responsible for the enhanced retrotransposon transcription.