To divide or not to divide? NAC8 (SOG1) as a key regulator of DNA damage response in barley (Hordeum vulgare L.)

We identified several new TILLING mutants of barley (Hordeum vulgare L.) with missense mutations in the HvNAC8 gene, a homolog of the SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1) gene in Arabidopsis thaliana. In Arabidopsis, SOG1 is the primary regulator of the DNA Damage Response (DDR) pathway. We aimed to transfer this knowledge to barley, an agriculturally important crop. Our detailed analysis of the hvnac8.k mutant revealed an impaired DDR pathway. The hvnac8.k mutant accumulates DNA damage under genotoxic stress induced by zeocin, but it also shows increased DNA damage under normal growth conditions. Despite this, the frequency of dividing cells in the root meristem of the mutant treated with zeocin is much less affected than in the wild type. This suggests that the mutant bypasses the typical DDR regulation, where cell division is halted to allow DNA repair following damage. We also analyzed our mutant under aluminum (Al3+) stress. Aluminum ions, present in acidic soils that constitute approximately 50 % of arable land, are a common stressor that significantly reduce barley yield. Al3 + is known to cause DNA damage and activate DDR. Consequently, we aimed to assess whether the hvnac8.k phenotype could confer a beneficial effect under aluminum stress, a widespread agronomic challenge. Our findings suggest that modulation of the DDR pathway has the potential to improve aluminum tolerance in barley.