Extreme drought stress tolerance in Arabis sagittata and Arabis nemorensis associates with a sharpened transcriptome response and an enhanced expression of stress-regulated miRNA408. PRJARABIS2024

• Plant species able to balance their competitive ability with tolerance to extreme environmental conditions can deliver crucial insight on molecular solutions to survive abiotic stress. This study focuses on Arabis nemorensis and Arabis sagittata, two species growing in competitive meadows. • We measured physiological parameters of both species during a dry-down experiment and used RNA-seq data to uncover molecular changes in response to drought stress. • Our findings revealed both species can tolerate extreme drought, wilting below 5%, with A. sagittata exhibiting a superior survival rate (90%) compared to A. nemorensis (49%). A. nemorensis forms larger rosettes that wilt more rapidly. Structural equation modeling indicates A. sagittata individuals reacting less to stress have higher survival rates, a relationship not observed in A. nemorensis, where survival is unrelated to stress reaction magnitude. Gene expression analysis shows significant differences in stress-related pathways, with the Dea(D/H) box gene, involved in miRNA biosynthesis, showing among the strongest differential response. Comparative miRNA analysis reveals their putative targets are enriched among drought stress-responsive genes. • This study identifies regulatory differences between two grassland species genotypes differing in drought tolerance. Understanding these molecular bases helps reveal how species endure abiotic stress while coping with the challenges of dense, competitive habitats