Comparative transcriptome analysis revealed the influence of sucrose on flavor and taste quality of Coffea arabica and C. canephora varieties

Coffea arabica (Arabica) and C. canephora (Robusta) are the most popular coffee species in the world, accounting for 99% of overall consumption of coffee beans. Arabica generally possesses better coffee quality than Robusta partly due its higher sucrose content. The flavor and taste (FT) of coffee, as important aspects of coffee quality, are mainly affected by the content of caffeine, phenolic acid and terpenoid compounds, which use sucrose as an important precursor. However, how sucrose affects the coffee FT remains unclear. In this study, coffee beans at different developmental stages from Arabica #161 (A161, high-sucrose variety) and Robusta #6 (R6, low-sucrose variety) were sampled to perform transcriptomic analysis. Most differentially expressed genes (DEGs) between them were enriched in sucrose-related metabolisms and the FT-related metabolism processes: caffeine biosynthesis, phenylpropanoid and flavonoid pathway, terpenoid metabolism. Thirty-four candidate DEGs probably contributed to the higher content of sucrose, anthocyanin and linalool in A161, and higher content of caffeine and carotenoid in R6. Generally, sucrose-related metabolisms were strongly associated with FT-related substance accumulation. The content of sucrose and its influence on the downstream secondary metabolism probably play important roles in the FT quality of coffee beans. Our results provide efficient targets for investigation regarding the influence of sucrose on FT quality of coffee beans.