Developmental differences in plant responses to DNA damage

Abstract

The developmental transition from seeds to adult plants faces continuous deleterious DNA modifications by endogenously or environmentally generated reactive molecules. The most adaptable developmental stage to this genotoxic stress is the seeds, while young seedlings are the most vulnerable. This leads us to hypothesise that the response to DNA damage (DDR) differs between plants at different developmental stages. To test this hypothesis, the transcriptional changes in response to X-ray irradiation were investigated between seeds and seedlings. These results were also contrasted between corresponding ATAXIA- TELANGIECTASIA MUTATED (ATM) wild- and mutant samples to study the potential differential roles ATM may play in modulating X-ray response in different plant developmental stages. The study reveals ATM-mediated checkpoint repressors and activators distinct to these two developmental stages. SMR5, a cell cycle inhibitor, shows high expression in seeds causing G1 arrest, while ANAC044 activation in seedlings promotes Rep-MYP accumulation leading to G2 arrest. Also, differential expression of DNA repair genes between seeds and seedlings such as BRCA1, RAD51, CYCB1-1, XRI1 and POLDs indicates that plants trigger different repair mechanisms depending on developmental stages. However, ATM-induced cell death (PCD) is characteristic of the X-ray response of seedlings but not seeds. This study identifies AT2G18193 that is highly responsive to ionising irradiation in seedlings and investigates its potential involvement in PCD. The findings pave the way for other lines of investigation to understand the role of AT2G18193 in DDR.