MtTdp2α-overexpression boosts the growth phase of Medicago truncatula cell suspension and increases the expression of key genes involved in the antioxidant response and genome stability

Aside from the great importance of Leguminosae in food and agriculture industry, legume model systems like Medicago truncatula are also essential tools to dissect complex cellular pathways and retrieve valuable information to other crops. Here, we investigated the roles played by the tyrosyl-DNA phosphodiesterase 2 alpha (MtTdp2 alpha) gene in cell viability and proliferation using M. truncatula suspension cultures. Our research hypothesis is that the overexpression of MtTdp2 alpha, implicated in the removal of transient topoisomerase/DNA covalent complexes, can impact on cell suspension viability. M. truncatula suspension cultures derived from leaf explants of MtTdp2 alpha-overexpressing lines and a control line carrying the empty vector were used. Our results showed that the control line reached the stationary growth phase by the fourth day of culture while the transgenic lines presented an extended exponential growth, reaching the stationary phase at day six following culture. The MtTdp2 alpha-overexpressing lines also showed increased viability as compared to the control line. The transcript levels of MtSOD, MtAPX, MtMT2, MtMRE11, MtNBS1, MtRad50, MtOGG1 and MtFPG were significantly enhanced in the transgenic lines as compared to control. Overall, our results show that the MtTdp2 alpha overexpression impacts in a positive manner on cell viability and proliferation in suspension cultures. Additionally, our study provides an insight on the suitability of M. truncatula cell suspension cultures as a promising alternative to evaluate potential protective mechanisms, with results comparable to those obtained when using whole plants.