Comparative genomic characterization and germination-associated expression of DET2 and CER10 related reductases in Chenopodium quinoa.

Genome annotations frequently group DEETIOLATED2 (DET2), ECERIFERUM10 (CER10), and related proteins under broad steroid-reductase-like designations, despite experimentally characterized members participating in distinct metabolic pathways associated with plant development and environmental responses. Here, we comparatively characterized DET2 and CER10 related reductases in Arabidopsis thaliana, Amaranthus hypochondriacus, and the allotetraploid crop Chenopodium quinoa. Phylogenetic analysis resolved five groups and clearly separated DET2-like and CER10-like proteins. Conserved motifs, exon-intron organization, local microsynteny, and predicted membrane topology and protein structure further supported this distinction and the retention of paired quinoa loci following allopolyploidization. Public expression datasets revealed marked transcriptional differences among family members. Germination and expression analyses were subsequently performed in the quinoa accessions Giza1 and Puno (Q04), which showed contrasting responses to 250 mM NaCl. Q04 maintained rapid germination under salinity, whereas Giza1 displayed a pronounced delay and reduced final germination. Among four genes analysed by RT-qPCR, CqCER10.1 showed the clearest accession- and time-dependent expression pattern. Under 250 mM NaCl, CqCER10.1 transcript levels were significantly higher in Q04 than in Giza1 during early germination, coinciding with the markedly faster and more successful germination of Q04 under salinity. In Giza1, CqCER10.1 accumulation occurred later, broadly following its delayed germination progression. CqCER10.2 and CqDET2.2 remained weakly expressed, whereas CqDET2.1 accumulated mainly at later stages. Given the contrasting behaviour of the CER10-like copies (homoeologs), comparative analysis of their upstream regions in the QQ74 reference genome revealed substantial sequence divergence together with locally conserved regions and putative cis-regulatory elements. Overall, these results refine the classification of DET2- and CER10 related reductases in quinoa and reveal pronounced transcriptional asymmetry among retained gene copies. CqCER10.1 expression was associated with the contrasting germination behaviour of Giza1 and Q04, particularly under salinity. Whether this association reflects developmental progression, accession-specific regulation under salinity, or both remains to be determined.