Cross-Dataset Transcriptomics Prioritize Histone-Modifier Candidates for Drought-Response Studies in Carex littledalei

Background/Objectives: Days of water deficit drive adaptive transcriptional repro-gramming, in which histone writers and erasers may participate. Histone-modifier cata-logues in Carex littledalei may include non-histone enzymes, and expression under poly-ethylene glycol (PEG) exposure cannot establish drought function. Methods: We re-curated a proposed gene set, reanalyzed an archived PEG expression matrix, and compared mapped Arabidopsis homolog groups across two independent RNA-sequencing datasets of drought-adaptive reprogramming (3 and 12 days). Results: Genome curation retained 84 of 116 proposed Carex loci. Five genes met an internal accession-by-exposure robustness filter in the 18-sample PEG matrix; missing raw reads, integer counts and untreated time-matched controls prevent a PEG-specific or soil-drought inference. Of 56 mapped Arabidopsis groups, 48 were estimable in both datasets. Thirteen groups had same-direction effects with a false-discovery rate below 0.05 in both datasets and stable directions after sample omission. Reciprocal pro-tein-sequence ranking supported 49 of 83 archived mappings, including ClHAF01, but did not validate orthology. No group survived Hartung–Knapp false-discovery-rate correction, and an exact sample-label test did not support dataset-independent pathway agreement (P = 0.295). Conclusions: ClHAF01 is the clearest single-locus priority; the ClJMJ01/04/10 group remains ambiguous despite a Carex PEG association for ClJMJ04. These results provide ranked candidates for functional testing, not evidence of his-tone-directed mechanism or causal drought tolerance.