Elevated temperatures impose transcriptional constraints on coffee genotypes and elicit intraspecific differences in thermoregulation

The projected impact of global warming on coffee production may require the heat-adapted genotypes in the next decades. To identify thermotolerance cellular strategies, we compared the effect of elevated temperature on two commercial Coffea arabica L. genotypes exploring leaf physiology, transcriptome and carbohydrate/protein composition. Growth temperatures were 23/19°C (day/night), as optimal condition (OpT), and 30/26°C (day/night) as a possible warmer scenario (WaT). The cv. Acaua showed lower levels of leaf temperature under both conditions compared to cv. Catuai, whereas slightly or no differences for other leaf physiological parameters. Therefore, to explore thermoregulatory pathways the leaf transcriptome was examined using RNAseq. Genotypes showed a marked number of differentially-expressed genes (DEGs) under OpT, however DEGs strongly decrease in both at WaT condition indicating a transcriptional constraint. DEGs responsive to WaT revealed shared and genotype-specific genes mostly related to carbohydrate metabolism. Under OpT, leaf starch content was greater in cv. Acaua although the levels of leaf starch, sucrose, and leaf protein decreased in both genotypes as WaT was imposed. These findings indicate that genotypes with a greater capacity to maintain carbohydrate homeostasis under temperature fluctuations could be more thermotolerant and which may be useful in breeding for a changing climate.