Genome and Transcriptome Sequencing of Oca (Oxalis tuberosa Molina) Reveals Photoperiod-Induced FT Homologs as Candidate Tuberigens

Oxalis tuberosa (oca) is a tuber crop native to the Andes, valued for its nutrition but understudied genetically. Its strict short-day (SD) tuberization suggests a photoperiodic control mechanism similar to that of potato, where an FT-like protein acts as a mobile “tuberigen” signal. To identify this key regulator, we generated a de novo genome assembly for oca using long- and short-read sequencing. Integrated transcriptomic analysis of leaves under long-day (LD) and SD conditions, along with stems, roots, and tubers, enabled gene annotation and expression analysis. Our study focused on the Phosphatidylethanolamine-Binding Protein (PEBP) gene family, the source of florigen and tuberigen signals. We identified 23 OtPEBP genes and characterized their expression patterns. Among these, we discovered three FT-like homologs that are specifically and strongly upregulated in leaves under SD conditions. We therefore propose these genes as the prime candidates for the mobile tuberigen signal in oca. This work provides the foundational genomic resource for O. tuberosa and advances our understanding of the conserved photoperiodic network controlling storage organ formation beyond the Solanaceae family.