Contrasting regulation of protein-coding genes and lncRNA homeologs in allotetraploid Coffea arabica.

Abstract

A chromosome-level Bourbon assembly revealed that protein-coding homeologs are predominantly co-regulated between subgenomes. In contrast, intergenic lncRNAs display a modest, but statistically consistent bias toward subgenome E across diverse developmental and stress contexts. Coffea arabica is an allotetraploid species derived from natural hybridization between C. canephora and C. eugenioides, which contributed the C and E subgenomes, respectively. This genomic origin poses major challenges for genome assembly, annotation, and the interpretation of gene regulation. In this study, a high-quality genome assembly of C. arabica was generated and annotated, with particular emphasis on identifying protein-coding genes and intergenic long non-coding RNAs (lincRNAs). Homeologous relationships between genes from the C and E subgenomes were established, providing a robust framework to investigate subgenomic conservation and regulatory divergence. Using an extensive collection of publicly available RNA-seq libraries spanning multiple developmental stages, tissues, and environmental conditions, the relative transcriptional contribution of each subgenome was evaluated. On a global scale, gene expression was largely balanced between subgenomes, with no consistent evidence of subgenome dominance. While protein-coding genes showed comparable regulatory behavior across subgenomes, lincRNAs exhibited a more asymmetric expression pattern, suggesting higher subgenome-specific expression that is interpreted here as a consistent directional tendency rather than as evidence of subgenome dominance. Together, these results provide new insights into the regulatory architecture of the C. arabica genome and establish a foundational genomic and transcriptomic resource for future functional studies and crop improvement efforts.