The understanding of acclimation strategies to low temperature and water availability is decisive to ensure coffee crop sustainability, since these environmental conditions determine the suitability ...of cultivation areas. In this context, the impacts of single and combined exposure to drought and cold were evaluated in three genotypes of the two major cropped species, Coffea arabica cv. Icatu, Coffea canephora cv. Apoatã, and the hybrid Obatã. Crucial traits of plant resilience to environmental stresses have been examined: photosynthesis, lipoperoxidation and the antioxidant response. Drought and/or cold promoted leaf dehydration, which was accompanied by stomatal and mesophyll limitations that impaired leaf C-assimilation in all genotypes. However, Icatu showed a lower impact upon stress exposure and a faster and complete photosynthetic recovery. Although lipoperoxidation was increased by drought (Icatu) and cold (all genotypes), it was greatly reduced by stress interaction, especially in Icatu. In fact, although the antioxidative system was reinforced under single drought and cold exposure (e.g., activity of enzymes as Cu,Zn-superoxide dismutase, ascorbate peroxidase, APX, glutathione reductase and catalase, CAT), the stronger increases were observed upon the simultaneous exposure to both stresses, which was accompanied with a transcriptional response of some genes, namely related to APX. Complementary, non-enzyme antioxidant molecules were promoted mostly by cold and the stress interaction, including α-tocopherol (in C. arabica plants), ascorbate (ASC), zeaxanthin, and phenolic compounds (all genotypes). In general, drought promoted antioxidant enzymes activity, whereas cold enhanced the synthesis of both enzyme and non-enzyme antioxidants, the latter likely related to a higher need of antioxidative capability when enzyme reactions were probably quite repressed by low temperature. Icatu showed the wider antioxidative capability, with the triggering of all studied antioxidative molecules by drought (except CAT), cold, and, particularly, stress interaction (except ASC), revealing a clear stress cross-tolerance. This justified the lower impacts on membrane lipoperoxidation and photosynthetic capacity under stress interaction conditions, related to a better ROS control. These findings are also relevant to coffee water management, showing that watering in the cold season should be largely avoided.
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Climate changes, mostly related to high temperature, are predicted to have major negative impacts on coffee crop yield and bean quality. Recent studies revealed that elevated air CO
mitigates the ...impact of heat on leaf physiology. However, the extent of the interaction between elevated air CO
and heat on coffee bean quality was never addressed. In this study, the single and combined impacts of enhanced CO
and temperature in beans of
cv. Icatu were evaluated. Plants were grown at 380 or 700 μL CO
L
air, and then submitted to a gradual temperature rise from 25°C up to 40°C during ca. 4 months. Fruits were harvested at 25°C, and in the ranges of 30-35 or 36-40°C, and bean physical and chemical attributes with potential implications on quality were then examined. These included: color, phenolic content, soluble solids, chlorogenic, caffeic and
-coumaric acids, caffeine, trigonelline, lipids, and minerals. Most of these parameters were mainly affected by temperature (although without a strong negative impact on bean quality), and only marginally, if at all, by elevated CO
. However, the CO
vs. temperature interaction strongly attenuated some of the negative impacts promoted by heat (e.g., total chlorogenic acids), thus maintaining the bean characteristics closer to those obtained under adequate temperature conditions (e.g., soluble solids, caffeic and
-coumaric acids, trigonelline, chroma, Hue angle, and color index), and increasing desirable features (acidity). Fatty acid and mineral pools remained quite stable, with only few modifications due to elevated air CO
(e.g., phosphorous) and/or heat. In conclusion, exposure to high temperature in the last stages of fruit maturation did not strongly depreciate bean quality, under the conditions of unrestricted water supply and moderate irradiance. Furthermore, the superimposition of elevated air CO
contributed to preserve bean quality by modifying and mitigating the heat impact on physical and chemical traits of coffee beans, which is clearly relevant in a context of predicted climate change and global warming scenarios.
Coffee is one of the world's most traded agricultural products. Modeling studies have predicted that climate change will have a strong impact on the suitability of current cultivation areas, but ...these studies have not anticipated possible mitigating effects of the elevated atmospheric CO2 because no information exists for the coffee plant. Potted plants from two genotypes of Coffea arabica and one of C. canephora were grown under controlled conditions of irradiance (800 μmol m(-2) s(-1)), RH (75%) and 380 or 700 μL CO2 L(-1) for 1 year, without water, nutrient or root development restrictions. In all genotypes, the high CO2 treatment promoted opposite trends for stomatal density and size, which decreased and increased, respectively. Regardless of the genotype or the growth CO2, the net rate of CO2 assimilation increased (34-49%) when measured at 700 than at 380 μL CO2 L(-1). This result, together with the almost unchanged stomatal conductance, led to an instantaneous water use efficiency increase. The results also showed a reinforcement of photosynthetic (and respiratory) components, namely thylakoid electron transport and the activities of RuBisCo, ribulose 5-phosphate kinase, malate dehydrogenase and pyruvate kinase, what may have contributed to the enhancements in the maximum rates of electron transport, carboxylation and photosynthetic capacity under elevated CO2, although these responses were genotype dependent. The photosystem II efficiency, energy driven to photochemical events, non-structural carbohydrates, photosynthetic pigment and membrane permeability did not respond to CO2 supply. Some alterations in total fatty acid content and the unsaturation level of the chloroplast membranes were noted but, apparently, did not affect photosynthetic functioning. Despite some differences among the genotypes, no clear species-dependent responses to elevated CO2 were observed. Overall, as no apparent sign of photosynthetic down-regulation was found, our data suggest that Coffea spp. plants may successfully cope with high CO2 under the present experimental conditions.
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Increasing exposure to unfavorable temperatures and water deficit imposes major constraints on most crops worldwide. Despite several studies regarding coffee responses to abiotic stresses, ...transcriptome modulation due to simultaneous stresses remains poorly understood. This study unravels transcriptomic responses under the combined action of drought and temperature in leaves from the two most traded species: Coffea canephora cv. Conilon Clone 153 (CL153) and C. arabica cv. Icatu. Substantial transcriptomic changes were found, especially in response to the combination of stresses that cannot be explained by an additive effect. A large number of genes were involved in stress responses, with photosynthesis and other physiologically related genes usually being negatively affected. In both genotypes, genes encoding for protective proteins, such as dehydrins and heat shock proteins, were positively regulated. Transcription factors (TFs), including MADS-box genes, were down-regulated, although responses were genotype-dependent. In contrast to Icatu, only a few drought- and heat-responsive DEGs were recorded in CL153, which also reacted more significantly in terms of the number of DEGs and enriched GO terms, suggesting a high ability to cope with stresses. This research provides novel insights into the molecular mechanisms underlying leaf Coffea responses to drought and heat, revealing their influence on gene expression.
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Understanding the effect of extreme temperatures and elevated air (CO2) is crucial for mitigating the impacts of the coffee industry. In this work, leaf transcriptomic changes were evaluated in the ...diploid C. canephora and its polyploid C. arabica, grown at 25 °C and at two supra-optimal temperatures (37 °C, 42 °C), under ambient (aCO2) or elevated air CO2 (eCO2). Both species expressed fewer genes as temperature rose, although a high number of differentially expressed genes (DEGs) were observed, especially at 42 °C. An enrichment analysis revealed that the two species reacted differently to the high temperatures but with an overall up-regulation of the photosynthetic machinery until 37 °C. Although eCO2 helped to release stress, 42 °C had a severe impact on both species. A total of 667 photosynthetic and biochemical related-DEGs were altered with high temperatures and eCO2, which may be used as key probe genes in future studies. This was mostly felt in C. arabica, where genes related to ribulose-bisphosphate carboxylase (RuBisCO) activity, chlorophyll a-b binding, and the reaction centres of photosystems I and II were down-regulated, especially under 42°C, regardless of CO2. Transcriptomic changes showed that both species were strongly affected by the highest temperature, although they can endure higher temperatures (37 °C) than previously assumed.
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Drought is a major constraint to plant growth and productivity worldwide and will aggravate as water availability becomes scarcer. Although elevated air CO2 might mitigate some of these effects in ...plants, the mechanisms underlying the involved responses are poorly understood in woody economically important crops such as Coffea. This study analyzed transcriptome changes in Coffea canephora cv. CL153 and C. arabica cv. Icatu exposed to moderate (MWD) or severe water deficits (SWD) and grown under ambient (aCO2) or elevated (eCO2) air CO2. We found that changes in expression levels and regulatory pathways were barely affected by MWD, while the SWD condition led to a down-regulation of most differentially expressed genes (DEGs). eCO2 attenuated the impacts of drought in the transcripts of both genotypes but mostly in Icatu, in agreement with physiological and metabolic studies. A predominance of protective and reactive oxygen species (ROS)-scavenging-related genes, directly or indirectly associated with ABA signaling pathways, was found in Coffea responses, including genes involved in water deprivation and desiccation, such as protein phosphatases in Icatu, and aspartic proteases and dehydrins in CL153, whose expression was validated by qRT-PCR. The existence of a complex post-transcriptional regulatory mechanism appears to occur in Coffea explaining some apparent discrepancies between transcriptomic, proteomic, and physiological data in these genotypes.
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As atmospheric CO
continues to rise to unprecedented levels, understanding its impact on plants is imperative to improve crop performance and sustainability under future climate conditions. In this ...context, transcriptional changes promoted by elevated CO
(eCO
) were studied in genotypes from the two major traded coffee species: the allopolyploid
(Icatu) and its diploid parent,
(CL153). While Icatu expressed more genes than CL153, a higher number of differentially expressed genes were found in CL153 as a response to eCO
. Although many genes were found to be commonly expressed by the two genotypes under eCO
, unique genes and pathways differed between them, with CL153 showing more enriched GO terms and metabolic pathways than Icatu. Divergent functional categories and significantly enriched pathways were found in these genotypes, which altogether supports contrasting responses to eCO
. A considerable number of genes linked to coffee physiological and biochemical responses were found to be affected by eCO
with the significant upregulation of photosynthetic, antioxidant, and lipidic genes. This supports the absence of photosynthesis down-regulation and, therefore, the maintenance of increased photosynthetic potential promoted by eCO
in these coffee genotypes.
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Climate changes boosted the frequency and severity of drought and heat events, with aggravated when these stresses occur simultaneously, turning crucial to unveil the plant response mechanisms to ...such harsh conditions. Therefore, plant responses/resilience to single and combined exposure to severe water deficit (SWD) and heat were assessed in two cultivars of the main coffee-producing species:
cv. Icatu and
cv. Conilon Clone 153 (CL153). Well-watered plants (WW) were exposed to SWD under an adequate temperature of 25/20°C (day/night), and thereafter submitted to a gradual increase up to 42/30°C, and a 14-d recovery period (Rec14). Greater protective response was found to single SWD than to single 37/28°C and/or 42/30°C (except for HSP70) in both cultivars, but CL153-SWD plants showed the larger variations of leaf thermal imaging crop water stress index (CWSI, 85% rise at 37/28°C) and stomatal conductance index (I
, 66% decline at 25/20°C). Both cultivars revealed great resilience to SWD and/or 37/28°C, but a tolerance limit was surpassed at 42/30°C. Under stress combination, Icatu usually displayed lower impacts on membrane permeability, and PSII function, likely associated with various responses, usually mostly driven by drought (but often kept or even strengthened under SWD and 42/30°C). These included the photoprotective zeaxanthin and lutein, antioxidant enzymes (superoxide dismutase, Cu,Zn-SOD; ascorbate peroxidase, APX), HSP70, arabinose and mannitol (involving
sugar synthesis), contributing to constrain lipoperoxidation. Also, only Icatu showed a strong reinforcement of glutathione reductase activity under stress combination. In general, the activities of antioxidative enzymes declined at 42/30°C (except Cu,Zn-SOD in Icatu and CAT in CL153), but HSP70 and raffinose were maintained higher in Icatu, whereas mannitol and arabinose markedly increased in CL153. Overall, a great leaf plasticity was found, especially in Icatu that revealed greater responsiveness of coordinated protection under all experimental conditions, justifying low PI
and absence of lipoperoxidation increase at 42/30°C. Despite a clear recovery by Rec14, some aftereffects persisted especially in SWD plants (
., membranes), relevant in terms of repeated stress exposure and full plant recovery to stresses.
Inundation, excessive precipitation, or inadequate field drainage can cause waterlogging of cultivated land. It is anticipated that climate change will increase the frequency, intensity, and ...unpredictability of flooding events. This stress affects 10-15 million hectares of wheat every year, resulting in 20-50% yield losses. Since this crop greatly sustains a population's food demands, providing ca. 20% of the world's energy and protein diets requirements, it is crucial to understand changes in soil and plant physiology under excess water conditions. Variations in redox potential, pH, nutrient availability, and electrical conductivity of waterlogged soil will be addressed, as well as their impacts in major plant responses, such as root system and plant development. Waterlogging effects at the leaf level will also be addressed, with a particular focus on gas exchanges, photosynthetic pigments, soluble sugars, membrane integrity, lipids, and oxidative stress.
Changes in the climate have led to the occurrence of extreme events that threaten the production of major crops, namely that of bread wheat (Triticum aestivum L.). Waterlogging imposed at the ...tillering stage can severely affect the yield, but several genotype features may counterbalance the negative impacts on yields. The aim of this work was to evaluate the effect of waterlogging on the number of fertile spikes, kernels per plant, and single kernel weight, as well as to assess the main culm and tiller participation in yields. We also investigated if the growth stages affected by stress would influence such traits. The study was conducted in climatized growth chambers using 23 genotypes from five distinct germplasm groups (Portuguese landraces, varieties with the introduced Italian germplasm, post-Green Revolution varieties with the introduced CIMMYT germplasm, advanced lines from the Portuguese wheat breeding program, Australian varieties). Variability was observed between and within the groups. Ten genotypes performed well under waterlogged conditions, showing promising results. Among these, GR-2 showed a rise in tiller yield, AdvL-3 in both the main culm and tiller yield, and the remaining ones displayed unaltered values in both the main culm and tillers. PL-1, PL-5, GR-1, GR-3, AdvL-2, Austrl-2, and Austrl-4 were able to compensate for the decreases observed for several traits, reaching harvest yield values that were unaffected in both the main culm and tillers. Rises in the tiller yield or in the tillers and main culm, GR-2 and AdvL-3 exhibited either stability or increases in all the studied parameters. Results also suggest a negative correlation between the growth stage reached during waterlogging and the effect of this stress on the number of spikes per plant, plant and tiller yield, kernel per spike (tillers), and single kernel weight (tillers). Our findings may contribute to a better understanding of wheat responses to waterlogging and to the development of solutions that mitigate the socio-economic impacts of 20–50% wheat yield reductions, thereby preserving the daily 20% supply of energy and protein required for human nutrition and global food security.
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