In plants, there are issues related to the effects of
gamma (γ)-rays that are still poorly explored, particularly
as concerns the biological response to irradiation delivered
at a low dose rate. In the present work, the effects of
exposure to increasing γ-ray total doses (6, 12, 25, and
50 Gy) delivered at 0.29 Gy min−1
, were evaluated in terms
of DNA damage sensing and repair in Medicago truncatula
proliferating cell suspension cultures. The profiles of reactive
oxygen species (ROS) and nitric oxide (NO) production, monitored
by fluorescent staining, were in agreement with the
transcriptional response of genes encoding the respiratory burst
oxidase-like protein C (MtRBOHC), nitrite reductase (MtNR),
the c... More
In plants, there are issues related to the effects of
gamma (γ)-rays that are still poorly explored, particularly
as concerns the biological response to irradiation delivered
at a low dose rate. In the present work, the effects of
exposure to increasing γ-ray total doses (6, 12, 25, and
50 Gy) delivered at 0.29 Gy min−1
, were evaluated in terms
of DNA damage sensing and repair in Medicago truncatula
proliferating cell suspension cultures. The profiles of reactive
oxygen species (ROS) and nitric oxide (NO) production, monitored
by fluorescent staining, were in agreement with the
transcriptional response of genes encoding the respiratory burst
oxidase-like protein C (MtRBOHC), nitrite reductase (MtNR),
the cytosolic isoform of ascorbate peroxidase (MtAPX), and a
type 2 metallothionein (MtMT2). The genotoxic effects were
assessed using the alkaline and neutral version of single cell gel
electrophoresis (SCGE), detecting the occurrence of SSBs
and DSBs. Independent on the irradiation dose, M. truncatula
cells always revealed the preferential repair of DSBs, while
the SSB repair was less effective. The DNA repair response
was investigated focusing on genes representative of different
DNA repair pathways. The overall picture derived from gene
profiling analysis highlights that M. truncatula cells can produce
an active response to IR-mediated genotoxic stress, as
indicated by the up-regulation of the DSB sensor MtMRE11
gene, the MtTop2 gene, and the MtOGG1gene, an essential
component of the base excision repair pathway. In contrast,
the MtTop1, MtTdp1 and MtTFIIS genes, believed to be part
of the nucleotide excision repair pathway, were significantly
down-regulated.
