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- Intrinsic non-stomatal resilience to drought of the photosynthetic apparatus in Coffea spp. is strengthened by elevated air [CO2]Publication . JN; Rodrigues, Ana P.; Lidon, Fernando C.; P. Pais, Isabel; Marques, Isabel; Gouveia, Duarte; ARMENGAUD, Jean; Silva, Maria J.; Martins, Sónia; Semedo, Magda C.; Dubberstein, Danielly; Partelli, Fábio Luiz; Reboredo, Fernando H.; Scotti-Campos, Paula; Ribeiro-Barros, Ana I; DaMatta, Fabio; Ramalho, José C.Growing water restrictions associated with climate changes constitute daunting challenges to crop performance. This study unveils the impacts of moderate (MWD) or severe (SWD) water deficit, and their interaction with air [CO2], on the photosynthetic apparatus of Coffea canephora Pierre ex A. Froehner cv. Conilon Clone 153 (CL153) and Coffea arabica L. cv. Icatu. Seven year-old potted plants grown under 380 (aCO(2)) or 700 mu l l (-1) (eCO(2)) [CO2] gradually reached predawn water potentials between -1.6 and -2.1 MPa (MWD), and below -3.5 MPa (SWD). Under drought, stomata closure was chiefly related to abscisic acid (ABA) rise. Increasing drought severity progressively affected gas exchange and fluorescence parameters in both genotypes, with non-stomatal limitations becoming gradually dominating, especially regarding the photochemical and biochemical components of CL153 SWD plants. In contrast, Icatu plants were highly tolerant to SWD, with minor, if any, negative impacts on the potential photosynthetic functioning and components (e.g., A(max), F-v/F-m, electron carriers, photosystems (PSs) and ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCO) activities). Besides, drought-stressed Icatu plants displayed increased abundance of a large set of proteins associated with the photosynthetic apparatus (PSs, light-harvesting complexes, cyclic electron flow, RuBisCO activase) regardless of [CO2]. Single eCO(2) did not promote stomatal and photosynthetic down-regulation in both genotypes. Instead, eCO(2) increased photosynthetic performance, moderately reinforced photochemical (PSs activity, electron carriers) and biochemical (RuBisCO, ribulose-5-phosphate kinase) components, whereas photoprotective mechanisms and protein abundance remained mostly unaffected. In both genotypes, under MWD, eCO(2) superimposition delayed stress severity and promoted photosynthetic functioning with lower energy dissipation and PSII impacts, whereas stomatal closure was decoupled from increases in ABA. In SWD plants, most impacts on the photosynthetic performance were reduced by eCO(2), especially in the moderately drought affected CL153 genotype, although maintaining RuBisCO as the most sensitive component, deserving special breeder's attention to improve coffee sustainability under future climate scenarios.
- Resilient and sensitive key points of the photosynthetic machinery of coffea spp. to the single and superimposed exposure to severe drought and heat stressesPublication . Dubberstein, Danielly; Lidon, Fernando C.; Rodrigues, Ana P.; Semedo, José N.; Marques, Isabel; Rodrigues, Weverton P.; Gouveia, Duarte; ARMENGAUD, Jean; Semedo, Magda C.; Martins, Sónia; Simoes-Costa, Maria C.; Moura, Isabel; Pais, Isabel P.; Scotti-Campos, Paula; Partelli, Fábio Luiz; E, Campostrini; Ribeiro-Barros, Ana I.; DaMatta, Fabio; Ramalho, José C.This study unveils the single and combined drought and heat impacts on the photosynthetic performance ofCoffea arabicacv. Icatu andC. canephoracv. 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 degrees C, day/night), and thereafter exposed to a gradual temperature rise up to 42/30 degrees C, followed by a 14-day water and temperature recovery. Single drought affected all gas exchanges (includingA(max)) and most fluorescence parameters in both genotypes. However, Icatu maintainedF(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 degrees C or 39/30 degrees C), likely associated with CEF in Icatu. Yet, at 42/30 degrees C the tolerance limit was exceeded. ReducedA(max)and increasedC(i)values reflected non-stomatal limitations of photosynthesis, agreeing with impairments in energy capture (F(0)rise), PSII photochemical efficiency, and RuBisCO and Ru5PK activities. In contrast to PSs activities and electron carrier contents, enzyme activities were highly heat sensitive. Until 37/28 degrees C, stresses interaction was largely absent, and drought played the major role in constraining photosynthesis functioning. Harsher conditions (SWD, 42/30 degrees C) exacerbated impairments to PSs, enzymes, and electron carriers, but uncontrolled energy dissipation was mitigated by photoprotective mechanisms. Most parameters recovered fully between 4 and 14 days after stress relief in both genotypes, although some aftereffects persisted in SWD plants. Icatu was more drought tolerant, with WW and SWD plants usually showing a faster and/or greater recovery than CL153. Heat affected both genotypes mostly at 42/30 degrees C, especially in SWD and Icatu plants. Overall, photochemical components were highly tolerant to heat and to stress interaction in contrast to enzymes that deserve special attention by breeding programs to increase coffee sustainability in climate change scenarios.
- Novel polyol-responsive monoclonal antibodies against extracellular b-D-Glucans from pleurotus ostreatusPublication . Semedo, Magda; Karmali, Amin; Martins, Sónia; Fonseca, Luís P.b-D-glucans from mushroom strains play a major role as biological response modifiers in several clinical disorders. Therefore, a specific assay method is of critical importance to find useful and novel sources of b-D-glucans with anti-tumor activity. Hybridoma technology was used to raise monoclonal antibodies (Mabs) against extracellular b-D-glucans (EBG) from Pleurotus ostreatus. Two of these hybridoma clones (3F8_3H7 and 1E6_1E8_B3) secreting Mabs against EBG from P. ostreatus were selected and 3F8_3H7 was used to investigate if they are polyol-responsive Mabs (PR-Mabs) by using ELlSA-elution assay. This hybridoma cell line secreted Mab of IgM class, which was purified in a single step by gel filtration chro-matography on Sephacryl S-300HR, which revealed a protein band on native PAGE with Mr of 917 kDa. Specificity studies of Mab 3F8_3H7 revealed that it recognized a common epitope on several b-D-glucans from different basidiomycete strains as determined by indirect EllSA and Western blotting under native conditions. This Mab exhibited high apparent affinity con-stant (KApp) for b-D-glucans from several mushroom strains. However, it revealed differential reactivity to some heat-treated b-D-glucans compared with the native forms suggesting that it binds to a conformation-sensitive epitope on b-D-glucan molecule. Epitope analysis of Mab 3F8_3H7 and 1E6_1E8_B3 was investigated by additivity index parameter, which revealed that they bound to the same epitope on some b-D-glucans and to different epitopes in other antigens. Therefore, these Mab can be used to assay for b-D-glucans as well as to act as powerful probes to detect conformational changes in these biopolymers.