Coffee plants respond to drought and elevated [CO2] through changes in stomatal function, plant hydraulic conductance, and aquaporin expression

Transcriptomic Leaf Profiling Reveals Differential Responses of the Two Most Traded Coffee Species to Elevated [CO2]

“…In fact, an increase of these genes is usually expected for removing misfolded or damaged proteins that accumulate as an exposure to abiotic stress [48]. Therefore, its down-regulation is consistent with the stress relief impact of eCO 2 found in Coffea species regarding drought [22] and heat [18,23] stresses, likely associated with the greater photochemical use of energy due to a higher carboxylation rate [13,20,22]. This would also decrease the photorespiration rate and the oxidative pressure at the chloroplast level, reducing the reactive oxygen species (ROS) formation and the excitation level in the photosystems [49,50].…”

“…In coffee leaves, aquaporin transcriptional genes seem not to significantly change the regulation of stomatal conductance (g s ), since it is barely affected under well-watered conditions and eCO 2 [13,20]. However, in another C. arabica genotype, faster stomatal closure rates (in well-watered conditions) and the maintenance of plant hydraulic conductance (in drought conditions) observed under eCO 2 were linked to a higher transcript abundance of most aquaporin genes [22], which can be seen as a preventive advantage if coffee plants are afterwards exposed to drought conditions.…”

“…Aquaporins, members of major intrinsic proteins (MIPs), were also found to be up-regulated in Icatu (Cc02_g05510 and Cc04_g17080; Table 1). Among other roles, aquaporins control the hydraulic conductance of cells and organs, managing water flux in and out of veins and stomatal guard cells, being part of the response to drought in plants, namely in coffee leaves [22]. They can also increase membrane permeability to CO 2 in mesophyll and stomatal guard cells, the latter increasing the effectiveness of RuBisCO, potentially influencing transpiration efficiency [46].…”

“…Overall, the exposure to eCO 2 supports important net photosynthesis increases between 34% and 49% under environmental-controlled conditions at 700 µmol mol −1 [20], ca. 40-60% at 550 µmol mol −1 under field conditions using a Free Air CO 2 Enrichment (FACE) facility [13], or even above 60% on Open Top Chambers (OTC) systems [22], under natural or semi-controlled environmental conditions, respectively. In fact, under eCO 2 , no photosynthetic and stomatal down-regulation is detected (the so-called negative acclimation) in coffee plants in contrast to a wide range of plant species, where photoassimilate accumulation and lower investment in photosynthetic components can compromise the stimulation effect of eCO 2 on photosynthesis [13,20].…”

“…In fact, under eCO 2 , no photosynthetic and stomatal down-regulation is detected (the so-called negative acclimation) in coffee plants in contrast to a wide range of plant species, where photoassimilate accumulation and lower investment in photosynthetic components can compromise the stimulation effect of eCO 2 on photosynthesis [13,20]. Additionally, eCO 2 improves the physiological status of coffee plants, which allows a greater coffee tolerance to heat [23,24] and drought [22], contributing to preserve coffee bean quality under supra-optimal temperature conditions [24].…”