Abstract
Quinoa (Chenopodium quinoa Willd.), an Andean crop with exceptional nutritional value, thrives in ecosystems exposed to intense ultraviolet-B (UV-B) radiation; yet the molecular mechanisms underlying its photoreception remain largely unknown. The UV Resistance locus 8 (UVR8) protein, a member of the Regulator of Chromosome Condensation 1 (RCC1) family, is the primary UV-B photoreceptor in plants. Here, we report the first in silico characterization of the RCC1 gene family in C. quinoa, aimed at identifying and structurally analyzing UVR8 homologs. Genomic analysis uncovered 40 CqRCC1 genes, exhibiting extensive structural diversity. Phylogenetic reconstruction identified two proteins, CqRCC1_20 and CqRCC1_23, as the closest homologs of AtUVR8 from Arabidopsis thaliana. Homology modeling revealed that CqRCC1_20 maintains the canonical seven-bladed β-propeller architecture of UVR8, whereas CqRCC1_23 carries a deletion leading to a six-bladed structure. Both isoforms retain the critical tryptophan residues (W233, W285, W337) and the C-terminal Valine-Proline (VP) motif required for photoperception and Constitutive Photomorphogenic 1 (COP1) interaction. Notably, the CqRCC1_23 model predicts fewer hydrogen bonds at the dimer interface and structural alterations at key regulatory interaction sites. Collectively, these results indicate that quinoa harbors functionally conserved UVR8 isoforms with structural divergence, such as CqRCC1_23, which may influence photoreceptor stability and enable a sustained UV-B response, potentially conferring an adaptive advantage in high-radiation environments.