Functional analyses revealed Pinus radiata CHLOROPLAST SENSOR KINASE as a key component in UV-B stress and development

• PrCSK identified as key in UV-B stress response. – • PrCSK overexpression improved growth and stress resilience. – • Amino acid and phenolic metabolism linked to UV-B recovery and PrCSK overexpression. – • PrCSK proposed as biomarker for pine UV-B tolerance and biomass production. Deciphering pine response mechanisms to UV-B stress enhanced by climate change is crucial to establish damage-reducing strategies and avoid losses for forestry sector. In this study, CHLOROPLAST SENSOR KINASE from Pinus radiata ( PrCSK ), previously identified as a potentially relevant component in UV-B stress response using a systems biology approach, was sequenced and used to generate overexpression and RNAi Arabidopsis thaliana lines to carry out functional validation studies employing phenotypical, physiological, and metabolomic analyses. Results demonstrated CSK evolutionary conservation between A. thaliana and P. radiata and its involvement in growth, development, and UV-B response and tolerance. Notably, overexpression lines showed enhanced growth, photosynthetic performance, and stress resilience linked to efficient water and carbon use, as well as resilient and efficient carbohydrate metabolism. Conversely, amino acid metabolism was essential for plant recovery when cellular damage increased due to CSK down-regulation, which also resulted in severe growth retardation. Moreover, secondary metabolism, represented by the accumulation of phenolic compounds, was also modified according to CSK expression levels. Overall, these results propose PrCSK as a valuable biomarker to select tolerant trees to adverse UV-B environmental conditions expected in the coming years, and to increase pine biomass and production to meet current and future global demand of timber products.