Enhancing growth and salinity stress tolerance in Arabidopsis with low-dose gamma radiation priming through a hormesis approach

Hormesis describes a biphasic response where low-dose exposure triggers positive physiological effects, while higher doses become detrimental. Priming, based on the concept of hormesis, suggests that low doses of a stressor induce beneficial adaptive responses, improving resilience to subsequent, more intense stressors in plants. Ionizing radiation is an interesting method for inducing priming (radio-priming) due to its potential to trigger molecular, biochemical, and physiological responses. Yet, the effects of varying radiation doses, applied at different developmental stages or to distinct plant materials, remain poorly understood, as do the long-term impacts on plant performance. This study evaluated the short- and long-term effects of gamma radiation on Arabidopsis thaliana growth and salinity stress response. Various plant materials were irradiated with increasing gamma doses (5–200 Gray, Gy), and subsequently exposed to salinity stress. Changes in growth, biochemical parameters, gene regulation, and fitness were compared in the different treatments. Low-dose gamma radiation (5–10 Gy) enhanced growth in non-saline and mild salinity conditions, increasing rosette area by 40 % in soaked seeds. The 5 Gy treatment also enhanced root growth under severe salinity stress. Conversely, doses exceeding 40 Gy were generally detrimental. Radio-primed plants under salinity stress showed rapid upregulation of LOX2, GLYI7, NHX2, and SOS1. Fitness analysis revealed that the 5 Gy-treated plants produced more seeds per silique under saline conditions. These results confirm that low-dose gamma radiation enhances salinity tolerance in A. thaliana, aligning with the hormesis hypothesis by promoting growth and activating stress-response genes without compromising plant fitness.