Search Results (48)

Increases in global temperatures, due to the climate change, are generating stress in most plant species. We hypothesize that young plants of Opuntia spp. adjust their Crassulacean acid metabolism (CAM) to the increase in nighttime temperature, allowing them to continue growing. The study was carried out in a greenhouse and laboratory of the Colegio de Postgraduados, Montecillo, Mexico. Three-month-old greenhouse-grown plants remained in a control environment with an average day/night temperature of 19.1/12.3 °C or were maintained in a chamber with increased nighttime temperatures averaging 19.1/18.9 °C day/night for 70 days. The experimental design was completely randomized with two treatments (control and high nighttime temperatures). After 70 days of high nighttime temperatures (HNT), at dawn (end of CAM phase I), plants had a 45% decrease in glucose (2.9 to 1.5 mg/100 mg dry tissue; dt) concentration and doubled and tripled fructose (0.43 to 0.95 mg/100 mg dt) and sucrose (0.47 to 0.09 mg/100 mg dt) concentrations. Glucose consumption may be related to the plant’s metabolic energy expenditure to overcome stress. The significant increase in fructose and sucrose is explainable by their function as signaling molecules among others. In contrast, photosynthetic efficiency, i.e., increased compared to the control, but the difference of acidity (end of phase I less phase III), the concentration of starch (1 mg/100 mg dt), free amino acids and soluble protein (1.2 mg/100 mg dt), wet and dry matter, stem height (60 cm) and width of the stem at dawn were not significantly affected. The adjustments in C and N metabolism and the non-significant effect on growth promoted by 70 HNT days may be related to adjustments in enzyme activities without changes in protein concentration. Young Opuntia spp. plants adjust their metabolism in response to increased nighttime temperatures, allowing them to maintain growth similar to that of the control. The results confirm the great potential of using the Opuntia genus in agriculture and genetic improvement in the face of the challenges posed by climatic change. Full article

Crassulacean acid metabolism (CAM) is a specialized photosynthetic pathway that enhances water-use efficiency by temporally separating nocturnal CO₂ uptake from daytime decarboxylation and carbon fixation. To uncover the regulatory mechanisms coordinating these temporal dynamics, we generated high-resolution, 48 h time-course transcriptomes for the CAM model Kalanchoe fedtschenkoi under both 12 h/12 h light/dark (LD) cycles and continuous light (LL). A rhythmicity analysis revealed that diel light cues are the dominant driver of transcript oscillations: 16,810 genes (54.3% of annotated genes) exhibited rhythmic expression only under LD, whereas just 399 genes (1.3%) remained rhythmic under LL. A smaller set of 3009 genes (9.7%) oscillated in both conditions, indicating that the intrinsic circadian clock sustains rhythmicity for a limited subset of the transcriptome. A gene co-expression network analysis revealed extensive integration between circadian clock components, core CAM pathway enzymes, and stomatal regulators, defining regulatory modules that coordinate metabolic and physiological timing. Notably, key hub genes associated with post-translational and post-transcriptional regulation, including the E3 ubiquitin ligase HUB2 and several pentatricopeptide repeat (PPR) proteins, act as central nodes in CAM-associated networks. This discovery implicates epigenetic and organellar regulation as previously unrecognized critical tiers of control in CAM. Together, our results support a regulatory model in which CAM rhythmicity is governed by both external light/dark cues and the endogenous circadian clock through multi-level control spanning transcriptional and protein-level regulation. To support community exploration, we also provide an interactive eFP (electronic Fluorescent Pictograph) browser for visualizing time-resolved gene expression profiles. Full article

Agriculture in semi-arid regions faces challenges, such as water scarcity and low soil fertility, making the forage cactus a highly important crop due to its crassulacean acid metabolism (CAM) pathway. The productivity of the forage cactus, however, depends on proper water and nutrient management, especially nitrogen. Despite its importance, there is little research into the effects of nitrogen fertilisation on productive, photochemical, physiological and biochemical parameters, or on intercropping systems. Increasing doses of nitrogen are assumed to enhance CAM pathway, improving productivity, gas exchange, photochemical efficiency and antioxidant accumulation, in addition to mitigating the effects of oxidative stress under adverse conditions. The experiment was conducted in Serra Talhada, Pernambuco, Brazil, in a randomised block design with four replications. Changes in the biometric, productive, photochemical, physiological and biochemical parameters were evaluated in forage cactus intercropped with sorghum (Sorghum bicolor) or pigeon pea (Cajanus cajan) subjected to different doses of nitrogen (0, 75, 150, 300 and 450 kg ha⁻¹). The results showed that nitrogen fertilisation promoted a higher photosynthetic rate and greater stomatal conductance, increased transpiration, and higher levels of pigment and soluble proteins, in addition to reducing lipid peroxidation. Our findings revealed that the cactus—pigeon pea intercropping system has better photosynthetic, enzymatic and productive performance at a dose of 150 kg N ha⁻¹, whereas the cactus—sorghum intercropping system required 450 kg N ha⁻¹ to achieve similar results. Overall, proper nitrogen management in intercropping systems can optimise the physiological performance and productivity of the forage cactus in semi-arid environments. Full article

Cacti of the genera Opuntia and Nopalea exhibit morphophysiological and biochemical characteristics that favor their adaptation to semiarid environments, such as crassulacean acid metabolism (CAM) and cladode succulence. These strategies reduce water loss and allow the maintenance of photosynthesis under stress conditions. In this study, we evaluated the seasonal variation in the physiological and photochemical responses of forage cactus clones grown in semiarid environments, considering the rainy, dry, and transition seasons. The net photosynthetic rate (P_n) and chlorophyll fluorescence parameters varied significantly as a function of water availability and microclimatic conditions. We found higher CO₂ assimilation rates during the rainy season, while the dry season resulted in a strong impairment of photosynthetic activity, with reductions of 65% in stomatal conductance, 37% in transpiration, 20% in maximum quantum efficiency of photosystem II, and 19% in the electron transport rate. Furthermore, during these periods, we observed an increase in initial fluorescence and non-photochemical dissipation, demonstrating the activation of photoprotective mechanisms against excess light energy. During the transition seasons, the cacti exhibited rapid adjustments in gas exchange and energy dissipation, indicating the adaptive plasticity of CAM pathway. The MIU (Nopalea cochenillifera (L.) Salm-Dyck), OEM (Opuntia stricta (Haw.) Haw.), and IPA (Nopalea cochenillifera (L.) Salm-Dyck) clones demonstrated greater resilience, maintaining greater stability in P_n, instantaneous water use efficiency, and photochemical parameters during the drought. In contrast, the OEA (Opuntia undulata Griffiths) clone showed high sensitivity to water and heat stress, with marked reductions in physiological and photochemical performance. In summary, the photosynthetic efficiency and chlorophyll fluorescence of CAM plants result from the interaction between water availability, air temperature, radiation, and genotypic traits. This study provides a new scientific basis for exploring the effects of environmental conditions on the carbon and biochemical metabolism of cacti grown in a semiarid environment. Full article

Drought stress is a major constraint on plant photosynthesis, growth, and yield, particularly in the context of increasingly frequent and severe extreme weather events driven by global climate change. Enhancing photosynthetic efficiency and abiotic stress tolerance is therefore essential for sustaining crop productivity. In this study, we functionally characterized Kalanchoë fedtschenkoi NAC83 (KfNAC83), a transcription factor derived from a heat-tolerant obligate crassulacean acid metabolism (CAM) species, by constitutively overexpressing it in the C₃ model plant Arabidopsis thaliana. Transgenic Arabidopsis lines overexpressing KfNAC83 exhibited significantly enhanced tolerance to water-deficit and NaCl stress, along with improved photosynthetic performance, biomass accumulation, and overall productivity. Transcriptomic analysis revealed that KfNAC83 overexpression increased key components of the jasmonate (JA) signaling pathway in both roots and shoots, suggesting a mechanistic link between KfNAC83 activity and enhanced abiotic stress responses. Additionally, the transgenic lines displayed increased nighttime decarboxylation activity, indicative of partial CAM-like metabolic traits. These findings demonstrate that KfNAC83 functions as a positive regulator of abiotic stress tolerance and growth, likely through modulation of jasmonate-mediated signaling and photosynthetic metabolism. This work highlights the potential of CAM-derived transcription factors for bioengineering abiotic stress-resilient crops in the face of climate change. Full article

The diffusive availability of CO₂ for photosynthesis is orders of magnitude lower in water than in air. This, and the low affinity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) for CO₂, implies that most marine photoautotrophs (cyanobacteria, microalgae, macroalgae and marine angiosperms or seagrasses) would be severely restricted were they to rely only on dissolved CO₂ for their photosynthetic performance. On the other hand, the ~120 times higher concentration of bicarbonate (HCO₃⁻) makes this inorganic carbon (Ci) form more available for utilisation by marine photosynthesisers. The most common way in marine macrophytes to utilise HCO₃⁻ is to convert it to CO₂ within acidic micro-zones of diffusion boundary layers (DBLs), including the cell walls, as catalysed by an outwardly acting carbonic anhydrase (CA). This would then generate an intra-chloroplastic (or for cyanobacteria intra-carboxysomal) CO₂-concentrating mechanism (CCM). Some algae (e.g., the common macroalgae Ulva spp.) and most cyanobacteria and microalgae feature direct HCO₃⁻ uptake as the most efficient CCM, while others (e.g., some red algae growing under low-light conditions) may rely on CO₂ diffusion only. We will in this contribution summarise our current understanding of photosynthetic carbon assimilation of submerged marine photoautotrophs, and in particular how their ‘biophysical’ CCMs differ from the ‘biochemical’ CCMs of terrestrial C₄ and Crassulacean Acid Metabolism (CAM) plants (for which there is very limited evidence in cyanobacteria, algae and seagrasses). Full article

Cactus pear (Opuntia-ficus indica (L.) Mill.) is an important agricultural crassulacean acid metabolism (CAM) species used as a source of food, forage, fodder, and secondary products and as a biofuel feedstock. However, the preferred source of nitrogen for this species, whether it be nitrate (NO₃⁻), ammonium (NH₄⁺), or a combination of both, is not well understood. To investigate the nitrate and ammonium preference of cactus pear, we grew cladodes in sand culture with deionized water as a control or with a cross-factorial set of nutrient solutions of 0.0, 2.5, 5.0, and 10.0 mmol of nitrate and/or ammonium for one month. We then assessed a set of physiological parameters including cladode growth, relative water content, chlorophyll, tissue acidity, soluble sugars, starch, nitrate, ammonium, glyoxylic acid, nitrate reductase activity, and nitrogen and carbon content. We found significant differences in all measured parameters except for cladode length, relative water content, and carbon content. Cladodes provided with only deionized water produced no new cladodes and showed decreased soluble sugar content, increased starch content, and increased tissue acidity. We also determined the relative steady-state transcript abundance of genes that encode enzymes involved in N metabolism and CAM. Compared with control cladodes, nutrient-supplied cladodes generally showed increased or variable steady-state mRNA expression of selected CAM-related genes and nitrogen-metabolism-related genes. Our results suggest that O. ficus-indica prefers fertilizers containing either equal concentrations nitrate and ammonium or more nitrate than ammonium. Full article

Temperature stress is one of the major limiting environmental factors that negatively impact global crop yields. Kalanchoë fedtschenkoi is an obligate crassulacean acid metabolism (CAM) plant species, exhibiting much higher water-use efficiency and tolerance to drought and heat stresses than C₃ or C₄ plant species. Previous studies on gene expression responses to low- or high-temperature stress have been focused on C₃ and C₄ plants. There is a lack of information about the regulation of gene expression by low and high temperatures in CAM plants. To address this knowledge gap, we performed transcriptome sequencing (RNA-Seq) of leaf and root tissues of K. fedtschenkoi under cold (8 °C), normal (25 °C), and heat (37 °C) conditions at dawn (i.e., 2 h before the light period) and dusk (i.e., 2 h before the dark period). Our analysis revealed differentially expressed genes (DEGs) under cold or heat treatment in comparison to normal conditions in leaf or root tissue at each of the two time points. In particular, DEGs exhibiting either the same or opposite direction of expression change (either up-regulated or down-regulated) under cold and heat treatments were identified. In addition, we analyzed gene co-expression modules regulated by cold or heat treatment, and we performed in-depth analyses of expression regulation by temperature stresses for selected gene categories, including CAM-related genes, genes encoding heat shock factors and heat shock proteins, circadian rhythm genes, and stomatal movement genes. Our study highlights both the common and distinct molecular strategies employed by CAM and C₃/C₄ plants in adapting to extreme temperatures, providing new insights into the molecular mechanisms underlying temperature stress responses in CAM species. Full article

Background: Crassulacean acid metabolism plants, such as Stenocereus spp., are climate warming-resilient crops used as food and for by-products elaboration in arid and semi-arid agroecosystems. A few studies on secondary metabolites have been conducted in pitayo fruit (PF), but there are no reports of these compounds in juice powders (JP) with (JPS) or without seeds (JPWS). This study was devoted to characterizing the juice powders (JPS and JPWS) of five pitayas with different flesh colors with regard to some phytochemical and functional attributes. Methods: The study was conducted with a completely random design with factorial arrangement in treatments (PF × JP). Results: Differences among pitayas were related to peel and flesh color attributes. Except for soluble dietary fiber, the remainder of the non-digestible carbohydrates were greater in JPS than in JPWS of all pitayas. Phenols and flavonoids were found to be the highest in the JPWS of all pitayas, whereas total saponins were the highest in JPS of the ‘Pink’ pitaya. The JPWS of the ‘Yellow’ and ‘Reddish-Purple’ pitayas had the highest content of betaxanthins and indicaxanthins, respectively. Antioxidant capacity was the highest in JPS of ‘Reddish-Purple’ and ‘Pink’ pitayas. Conclusions: Except for some phenolic compounds, the study suggests that pitayas’ JPS would benefit human health when freshly consumed or as elaborated by-products. Full article

There are a number of rather anecdotal reports of plant growth on power cables in the Americas, but until now there has been no systematic attempt to gauge the geographical extension of this phenomenon nor a documentation of the diversity of species found there. Using observations from the participatory science data platform iNaturalist and the scientific literature, we document almost 700 occurrences of more than 40 species of vascular plants and three lichen species on power cables with a geographical distribution over 7000 km from the southern United States to northern Argentina. Based on these observations we discuss the ecological conditions of plant growth on power cables in terms of climate; elevational distribution; and the morphological, physiological, and life history traits that allow the observed set of species to thrive on this anthropic structure. Full article

Most of the aquatic vegetation produces organic substances via the C3 photosynthetic pathway (mosses, isoetids—Lobelia dortmanna L., Luronium natans (L.) Raf., and vascular plants) or Crassulacean acid metabolism (CAM, e.g., Littorella uniflora (L.) Asch. and Isoëtes lacustris L.) or by their ability to use HCO₃⁻ via carbon concentration mechanisms (CCMs—some elodeids and charophytes). Differentiating these predominant photosynthetic pathways in aquatic vegetation based on their organic matter (OM) carbon stable isotopes (δ¹³C_ORG) is a complex task, in contrast to terrestrial plants. This study investigates the OM deposition, characterized by δ¹³C_ORG values in 10 macrophyte species with different photosynthetic pathways (C3, CAM, and CCM) collected from 14 softwater Lobelia lakes in northern Poland. The higher δ¹³C_ORG values distinguish the CCM group, indicating their use of ¹³C-enriched HCO₃¯ in photosynthesis. CAM species show slightly higher δ¹³C_ORG values than C3, particularly in lower pH lakes. Principal component analysis of isotopic and environmental data did not yield clear distinctions by the groups, but still, they significantly differ in light of analyzed parameters and isotopic signals (PRMANOVA = 5.08, p < 0.01; K-W H = 27.01, p < 0.001). The first two PCA dimensions showed that the water pH and Ca²⁺ concentration positively influenced δ¹³C values. The influence of light conditions on δ¹³C_ORG values revealed by third PCA components seems to also be important. In summary, northern Polish Lobelia lakes serve as a key differentiation point between vegetation employing CCMs and those relying on C3/CAM photosynthesis without HCO₃⁻ utilization, providing insights into transitions in plant communities within these ecosystems. Full article

Abiotic stresses often occur simultaneously, and the tolerance mechanisms of plants to combined multiple abiotic stresses remain poorly studied. Extremophytes, adapted to abiotic stressors, might possess stress-adaptive or -responsive regulators that could enhance multiple abiotic stress resistance in crop plants. We identified an NF-YB transcription factor (TF) from the heat-tolerant obligate Crassulacean acid metabolism (CAM) plant, Kalanchoe fedtschenkoi, as a potential regulator of multiple abiotic stresses. The KfNF-YB3 gene was overexpressed in Arabidopsis to determine its role in multiple abiotic stress responses. Transgenic lines exhibited accelerated flowering time, increased biomass, larger rosette size, higher seed yield, and more leaves. Transgenic lines had higher germination rates under combined NaCl, osmotic, and water-deficit stress treatments compared to control plants. They also showed enhanced root growth and survival under simultaneous NaCl, osmotic, water-deficit, and heat stress conditions in vitro. Interestingly, potted transgenic lines had higher survival rates, yield, and biomass under simultaneous heat, water-deficit, and light stresses compared to control plants. Altogether, these results provide initial insights into the functions of a CAM-related TF and its potential roles in regulating multiple abiotic stress responses. The CAM abiotic stress-responsive TF-based approach appears to be an ideal strategy to enhance multi-stress resilience in crop plants. Full article

Climate change-induced prolonged water stress (WS) affects crassulacean acid metabolism photosynthesis in pitaya (Hylocereus), limiting crop productivity through insufficient photosynthate. To document how WS/rehydration affects diel photosynthesis, red-fleshed pitaya (H. polyrhizus) micropropagules were studied for 5 weeks in a mannitol-induced water potential gradient replaced with moderate (MWS; −1.0 MPa in week 2; −0.5 MPa for the rest) or intensified (IWS; −1.0 and −1.5 MPa in weeks 2 and 3; −0.5 MPa for the rest) WS in vitro. Net photosynthetic rate (Pn) and integrated net CO₂ uptake (INCU) were measured using an Arduino-based photosynthesis system. Micropropagules under MWS had similar Pn in weeks 5 and 1, whereas the control (−0.5 MPa) increased. Pn recovery did not occur after IWS. The average relative INCU was similar in the control and MWS, but lower in IWS. The Pn difference increased with WS, becoming more evident at dawn (Phase II), evening (Phase IV), and predawn the next day (Phase I), and occurred earlier in Phases IV and I under IWS. MWS did not reduce photosynthesis, demonstrating that the photosynthetic regulation could respond to short-term WS in pitaya and indicating the potential of watering for Pn recovery at evening and predawn under IWS. Full article

Phosphoenolpyruvate carboxylase (PEPC) gene family plays a crucial role in both plant growth and response to abiotic stress. Approximately half of the Orchidaceae species are estimated to perform CAM pathway, and the availability of sequenced orchid genomes makes them ideal subjects for investigating the PEPC gene family in CAM plants. In this study, a total of 33 PEPC genes were identified across 15 orchids. Specifically, one PEPC gene was found in Cymbidium goeringii and Platanthera guangdongensis; two in Apostasia shenzhenica, Dendrobium chrysotoxum, D. huoshanense, Gastrodia elata, G. menghaiensis, Phalaenopsis aphrodite, Ph. equestris, and Pl. zijinensis; three in C. ensifolium, C. sinense, D. catenatum, D. nobile, and Vanilla planifolia. These PEPC genes were categorized into four subgroups, namely PEPC-i, PEPC-ii, and PEPC-iii (PTPC), and PEPC-iv (BTPC), supported by the comprehensive analyses of their physicochemical properties, motif, and gene structures. Remarkably, PEPC-iv contained a heretofore unreported orchid PEPC gene, identified as VpPEPC4. Differences in the number of PEPC homolog genes among these species were attributed to segmental duplication, whole-genome duplication (WGD), or gene loss events. Cis-elements identified in promoter regions were predominantly associated with light responsiveness, and circadian-related elements were observed in each PEPC-i and PEPC-ii gene. The expression levels of recruited BTPC, VpPEPC4, exhibited a lower expression level than other VpPEPCs in the tested tissues. The expression analyses and RT-qPCR results revealed diverse expression patterns in orchid PEPC genes. Duplicated genes exhibited distinct expression patterns, suggesting functional divergence. This study offered a comprehensive analysis to unveil the evolution and function of PEPC genes in Orchidaceae. Full article

Elucidation of different vegetation energy partitioning and environmental control factors at the agro-ecosystem levels is critical for better understanding and scientific management of farmland. Pineapple (Ananas comosus (L.) Merril) is a tropical plant widely cultivated in the southern subtropical region of China; however, the energy partitioning of crassulacean acid metabolism (CAM) plants like pineapple and their interactions with the environment remain not well understood. In this study, we investigated the energy partitioning patterns of pineapple fields and latent heat flux (LET) response to environmental factors using the Bowen ratio energy balance system and meteorological observation field data. The results showed that the CAM plant pineapple energy partitioning was significantly different from the common C₃ and C₄ crops during the study period, which was mainly attributed to the complex interactions between CAM plant transpiration and the environment. Specifically, sensible heat flux was the main component of net radiation (R_n), followed by the LET, accounting for 65.0% and 30.8% of the R_n, respectively. Soil heat flux accounts for a very small fraction (4.2%). The mean values of the Bowen ratio were 2.09 and 1.41 for sunny and cloudy days during the daytime and 0.74 and 0.46 at night, respectively. LET is a key factor in responding to crop growth status and agricultural water management, and the path analysis indicates that its variation is mainly influenced directly by R_n with a direct path coefficient of 0.94 on sunny days, followed by vapor pressure deficit, air temperature and relative humidity, which indirectly affect LET through the R_n pathway, whereas soil moisture and wind speed have a low effect on LET. On cloudy days, the effect of R_n on LET was overwhelmingly dominant, with a direct path coefficient of 0.91. The direct path coefficients of the remaining factors on LET were very small and negative. Overall, this study is an important reference for enhancing the impact of pineapple as well as CAM plants on the surface energy balance and regional climate. Full article