The study shows that silencing of NOR2 rRNA genes in Arabidopsis thaliana depends primarily on CHH-context cytosine methylation, particularly mediated by CMT2 and the chromatin remodeler DDM1, rather than CG or CHG methylation. Comparative promoter analysis revealed a prevalence of CHH sites in plant rDNA promoters, explaining why CHH methylation mutants disrupt NOR2 silencing more strongly, while NOR2 loci are hyper‑methylated and more condensed than NOR4.

The study shows that drought triggers ABA accumulation and JA reduction in sorghum roots, accompanied by transcriptional activation of genes linked to mineral homeostasis, hormone signaling, and osmotic regulation, while Fe supplementation enhances ferritin expression and mitigates oxidative stress. Drought also diminishes root bacterial diversity but enriches beneficial taxa such as Burkholderia, whereas fungal diversity remains stable, and functional profiling reveals shifts toward phototrophy, methylotrophy, and nitrate reduction. These findings highlight ferritin’s protective role and suggest specific bacterial inoculants for improving sorghum drought resilience.