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bioRxiv · 10.64898/2025.12.13.694152

Genomic Structural Variation Underlies Cell-Type-Specific Betacyanin Variegation in Chenopodium quinoa

Zhang, Z.·Wang, Y.·Hu, X.·Yu, T.·Feng, Y.·Zhang, J.·Zhang, T.·Feng, G.·Zhang, H.
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Abstract

The allotetraploid crop quinoa (Chenopodium quinoa) accumulates red/violet betacyanins, which function as vital stress-mitigating antioxidants. We investigated the genetic basis of red/green variegation observed in the aerial organs of the P0429 accession. We demonstrated that this color mosaic is primarily localized to the epidermal bladder cells (EBCs), with red EBCs accumulating [~]50-fold higher betacyanin levels than colorless EBCs. Cell-type-specific RNA-sequencing of EBCs identified the cytochrome P450 gene Cqu0091301 (CYP76AD) as the dominant and rate-limiting factor, exhibiting strong upregulation in red EBCs. This high pigmentation requires a specific structural variation in the P0429 accession: a [~]4-kb genomic insertion that restores the full functionality of Cqu0091301, which is otherwise truncated and non-functional in common reference genomes. Genomic analysis reveals that Cqu0091301 is part of a CYP76AD-DODA gene cluster. Notably, expression analysis revealed functional divergence between the quinoa subgenomes, with B-subgenome CYP76AD genes highly dominant in EBCs, while A-subgenome homologs were preferentially expressed in other tissues. Our results establish a clear link between structural genomic variation and cell-type-specific betalain biosynthesis, providing molecular insight into pigment regulation and subgenome specialization in allotetraploid quinoa.

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Zhang, Z., Wang, Y., Hu, X., Yu, T., Feng, Y., Zhang, J., Zhang, T., Feng, G., Zhang, H.. 2025-12-16. Genomic Structural Variation Underlies Cell-Type-Specific Betacyanin Variegation in Chenopodium quinoa. https://doi.org/10.64898/2025.12.13.694152

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