MtTdp1?-depleted Medicago truncatula plants show reduced cuticle permeability and altered expression of defense genes

The link between the MtTdp1 alpha (tyrosyl-DNA phosphodiesterase) gene, involved in the repair of DNA topoisomerase I mediated DNA damage, and the plant defense response has been investigated in MtTdp1 alpha-depleted Medicago truncatula transgenic lines obtained by intron-spliced hairpin RNA approach, compared to the control line (CTRL, empty vector). Reduction of cuticle permeability highlighted by chlorophyll efflux assays positively correlated with the level of MtTdp1 alpha gene silencing. The increased cuticle thickness was confirmed by transmission electron microscopy, which revealed an apparent expansion of the epicuticular waxes deposited on the outer surface. RNA-Seq analysis, carried out in the MtTdp1 alpha-depleted plants, revealed the different expression of resistance (R) genes, PAMP (pathogen-associated-molecular pattern) triggered immunity (PTI) genes and transcription factors (TFs) involved in the regulation of the plant defense response.