Resilient and Sensitive Key Points of the Photosynthetic Machinery of Coffea spp. to the Single and Superimposed Exposure to Severe Drought and Heat Stresses

Abstract

This study unveils the single and combined drought and heat impacts on the photosynthetic performance of Coffea arabica cv. Icatu and C. canephora cv. Conilon Clone 153 (CL153). Well-watered (WW) potted plants were gradually submitted to severe water deficit (SWD) along 20 days under adequate temperature (25/20°C, day/night), and thereafter exposed to a gradual temperature rise up to 42/30°C, followed by a 14-day water and temperature recovery. Single drought affected all gas exchanges (including A max) and most fluorescence parameters in both genotypes. However, Icatu maintained F v /F m and RuBisCO activity, and reinforced electron transport rates, carrier contents, and proton gradient regulation (PGR5) and chloroplast NADH dehydrogenase-like (NDH) complex proteins abundance. This suggested negligible non-stomatal limitations of photosynthesis that were accompanied by a triggering of protective cyclic electron transport (CEF) involving both photosystems (PSs). These findings contrasted with declines in RuBisCO and PSs activities, and cytochromes (b 559 , f, b 563) contents in CL153. Remarkable heat tolerance in potential photosynthetic functioning was detected in WW plants of both genotypes (up to 37/28°C or 39/30°C), likely associated with CEF in Icatu. Yet, at 42/30°C the tolerance limit was exceeded. Reduced A max and increased C i

A Transcriptomic Approach to Understanding the Combined Impacts of Supra-Optimal Temperatures and CO2 Revealed Different Responses in the Polyploid Coffea arabica and Its Diploid Progenitor C. canephora

“…This is consistent with the findings in rice [ 48 ], wheat [ 49 ], and maize [ 50 ] suggesting that temperature stress has a general conserved response across plant lineages, where binding and folding play an important role in the ability of a plant to cope with stress. At 37 °C we also found an enrichment in the up-regulation of thylakoid, photosystem, and photosynthesis in both species and under CO 2 conditions ( Figure 5 A), in line with previous results demonstrating the intrinsic ability of these plants to maintain the photosynthetic activity up to 37 °C, regardless of air CO 2 but with a clear negative impact at 42 °C [ 14 , 30 ]. This would explain why these categories are no longer enriched at that temperature.…”

“…Acauã and Catuaí) where the number of DEGs decreased as a response to elevated temperatures (23/19 °C vs. 30/26 °C [ 35 ]). Nevertheless, these differences might also be due to the short period of the experimental trial (e.g., 4 weeks [ 35 ] vs. 10 months in our present study), and to the physiological performance of coffee plants which is frequently higher at 30 °C than at 25 °C [ 14 , 30 ].…”

“…A strong difference was found in the response to the studied temperatures, since gene enrichment in down-regulated DEGs was mostly felt at 37 °C than at 42 °C, in both species ( Figure 5 B). Previous reports showed that these genotypes retain the ability to cope with temperatures as high of 37 °C (or even 39 °C), but at 42 °C the tolerance capability is overcome [ 14 , 30 ]. In fact, at 37 °C, down-regulated DEGs showed almost no enriched categories under aCO 2 while under eCO 2 , Icatu and especially CL153 showed an enrichment in general activities as oxidoreductase activity acting on paired donors with the incorporation or reduction of molecular oxygen (GO:0016705).…”

“…Furthermore, some experiments reported that if temperature rises gradually (from 24 °C up to 33–35 °C) and considering a sufficiently long acclimation time, C. arabica plants can increase their photosynthesis up to temperatures around 30 °C, displaying the same efficiency as observed at 24 °C [ 28 ]. Also, some genotypes can maintain full photosynthetic functioning at temperatures as high as 35 °C [ 15 ] or even up to 39 °C for a short number of days [ 14 , 30 ]. The maintenance of high photosynthetic efficiency suggests the absence of negative effects on the photosynthetic structures, which agrees to some extent with the absence of membrane permeability changes after a short-time exposure up to 50 °C, as found in C. arabica [ 31 ].…”

Impact of drought associated with high temperatures on Coffea canephora plantations: a case study in Espírito Santo State, Brazil

“…However, little is known about the effects of thermal stress on the productive performance of C. canephora . The studies so far have focused on identifying their effects on photosynthesis and in leaf morphological and metabolic characteristics 51 , being practically inexistent the studies that evaluated the effects of thermal stress on production. An interesting study of Kath et al 52 about this topic brings new insight over thermal stress on Coffea canephora yield.…”