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Drought stress is the main cause of agricultural crop loss in the world. However, plants have developed mechanisms that allow them to tolerate drought stress conditions. At cellular level, drought stress induces changes in metabolite accumulation, including increases in anthocyanin levels due to upregulation of the anthocyanin biosynthetic pathway. Recent studies suggest that the higher anthocyanin content observed under drought stress conditions could be a consequence of a rise in the abscisic acid (ABA) concentration. This plant hormone crosses the plasma membrane by specific transporters, and it is recognized at the cytosolic level by receptors known as pyrabactin resistance (PYR)/regulatory component of ABA receptors (PYR/RCARs) that regulatedownstream components. In this review, we discuss the hypothesis regarding the involvement of ABA in the regulation of microRNA156 (miRNA156), which is upregulated as part of dehydration stress responsiveness in different species. The miRNA156 upregulation produces a greater level of anthocyanin gene expression, forming the multienzyme complex that will synthesize an increased level of anthocyanins at the cytosolic face of the rough endoplasmic reticulum (RER). After synthesis, anthocyanins are transported from the RER to the vacuole by two possible models of transport: (1) membrane vesicle-mediated transport, or (2) membrane transporter-mediated transport. Thus, the aim was to analyze the recent findings on synthesis, transport and the possible mechanism by which ABA could increase anthocyanin synthesis under drought stress conditions potentially throughout microRNA156 (miRNA156).

Salicylic acid (SA) has been shown to ameliorate drought stress. However, physiological and biochemical mechanisms involved in drought stress tolerance induced by SA in plants have not been well understood. Thus, this study aimed to study the role of SA application on enzymatic and non-enzymatic antioxidants, photosynthetic performance, and plant growth in A. chilensis plants subjected to moderate drought stress. One-year-old A. chilensis plants were subjected to 100% and 60% of field capacity. When plants reached moderate drought stress (average of stem water potential of −1.0 MPa, considered as moderate drought stress), a single SA application was performed on plants. Then, physiological and biochemical features were determined at different times during 14 days. Our study showed that SA application increased 13.5% plant growth and recovered 41.9% AN and 40.7% gs in drought-stressed plants on day 3 compared to drought-stressed plants without SA application. Interestingly, SOD and APX activities were increased 85% and 60%, respectively, in drought-stressed SA-treated plants on day 3. Likewise, SA improved 30% total phenolic content and 60% antioxidant capacity in drought-stressed A. chilensis plants. Our study provides insight into the SA mechanism to tolerate moderate drought stress in A. chilensis plants.

In this study, the physiological performance and fruit quality responses of the highbush blueberry (Vaccinium corymbosum) cultivar Legacy to high temperatures (HTs) were evaluated in a field experiment. Three-year-old V. corymbosum plants were exposed to two temperature treatments between fruit load set and harvest during the 2022/2023 season: (i) ambient temperature (AT) and (ii) high temperature (HT) (5 °C ± 1 °C above ambient temperature). A chamber covered with transparent polyethylene (100 µm thick) was used to apply the HT treatment. In our study, the diurnal temperature was maintained with a difference of 5.03 °C ± 0.12 °C between the AT and HT treatments. Our findings indicated that HT significantly decreased CO2 assimilation (Pn) by 45% and stomatal conductance (gs) by 35.2% compared to the AT treatment. By contrast, the intercellular CO2 concentration (Ci) showed higher levels (about 6%) in HT plants than in AT plants. Fruit quality analyses revealed that the fruit weight and equatorial diameter decreased by 39% and 13%, respectively, in the HT treatment compared to the AT treatment. By contrast, the firmness and total soluble solids (TSS) were higher in the HT treatment than in the AT treatment. Meanwhile, the titratable acidity showed no changes between temperature treatments. In our study, Pn reduction could be associated with stomatal and non-stomatal limitations under HT treatment. Although these findings improve our understanding of the impact of HTs on fruit growth and quality in V. corymbosum, further biochemical and molecular studies are need.

Covering material is an important tool to reduce damage from extreme weather events, especially in horticultural species. However, physiological and biochemical responses to covering material are still limited in woody plants. Thus, this study aimed to evaluate covering material effects on photosynthetic and antioxidant performance in blueberry cv. Legacy to high‐density polyethylene (HDPE) and low‐density polyethylene (LDPE) covering treatments under field conditions during two consecutive seasons. Our results showed that net photosynthesis (Pn) was reduced in LDPE compared to uncovered treatment during the first season. Interestingly, Pn increased 10% in HDPE compared to uncovered and LDPE treatments. Stomatal conductance (gs) was not affected by covering material; meanwhile, the transpiration (E) only showed a 22% increment in LDPE. HDPE exhibited the highest chlorophyll a in the 2018/2019 season compared to the uncovering treatment, as well as chlorophyll b and chlorophyll a/b ratio, but during the 2017/2018 season. A tendency to decrease chlorophyll a level in uncovered plants and LDPE treatment was observed during the 2018/2019 season. Antioxidant activity showed no differences among covering materials. By contrast, phenols increased in LDPE treatment followed by control plants, showing HDPE treatment the lower values during 2018/2019. In conclusion, this study demonstrated that blueberry plants subjected to HDPE treatment showed better Pn and chlorophyll levels than uncovered and LDPE treatments, which could be associated with the diffuse transmittance in HDPE, whereas a high E and phenols were observed in LDPE, whereas intrinsic water use efficiency was lower, which is related to high direct transmittance in this covering material during the summer season. Core Ideas High‐density polyethylene (HDPE) showed better Pn and chlorophyll levels than uncovered and low‐density polyethylene (LDPE) treatment. High transpiration and phenols concentration were observed in LDPE, related to high direct transmittance in this covering material. A low WUEint were observed in LDPE compared to HDPE, particularly during the second season.

Manganese (Mn) is an essential micronutrient for plants; however, in excess, it can have negative effects on their physiological and biochemical characteristics. We evaluate photosynthetic performance, antioxidant activity, and organic acid exudations to clarify the mechanisms involved in highbush blueberry ( Vaccinium corymbosum L.) under Mn excess. One-year-old plants of V . corymbosum cultivars (Legacy, Brigitta, and Bluegold) were grown in hydroponic solution with 2, 10, 50, 250, 500, and 1000 μM of Mn treatments for 25 days. Plant growth as shoot and root biomass, Mn content, photosynthetic performance [photochemical efficiency of PSII, CO 2 assimilation, and stomatal conductance (g s )], lipid peroxidation, radical scavenging activity, superoxide dismutase activity, and organic acid exudations were analyzed. Mn excess triggered detrimental effects in terms of plant growth, photochemical efficiency, and CO 2 assimilation, as well as in biochemical features in V . corymbosum cultivars. Despite Legacy decreasing its photosynthesis, plant growth was maintained throughout the experiment; by contrast, Brigitta maintained photosynthesis and growth despite the decrease in stomatal conductance (g s ). Meanwhile, Bluegold presented the lowest level in net photosynthesis and photochemical processes and an increase in lipid peroxidation. Oxalate and citrate were the most important organic acid anions in Legacy and Brigitta, gradually increasing their concentration with the enhancement of Mn doses. Our study demonstrated that Mn excess negatively and differently affects the physiological and biochemical features of V . corymbosum cultivars, with Legacy and Brigitta being Mn-resistant and Bluegold Mn-sensitive.

Highbush blueberry fruits are very perishable, decreasing quality and antioxidant potential during postharvest storage. Several preservation technologies to improve blueberries shelf life have been proposed. We evaluated the impact of fruit cold-storage and UV-C irradiation postharvest treatments on quality and antioxidant properties of berries from different blueberry cultivars grown in southern Chile. Berries of Legacy, Brigitta, and Bluegold cultivars were subjected to cold-storage (4 °C, for 28 days) or UV-C irradiation (2.3 or 4.6 kJ m?2) before cold-storage (4 °C) during 5 or 10 days. Then, fresh weight (FW), total soluble solids (TSS), titratable acidity (TiA), radical scavenging activity (RSA), total phenol content (TPC), and total anthocyanin content (TAC) were analyzed in whole fruits. During cold-storage, fruit FW was reduced (~ 20%) from day 7 onward, without variations among storage times. The irradiation of fruits with UV-C light also tends to reduce berry FW (~ 20%), but only in cultivar Legacy and in response to the highest UV-C doses. No significant differences were found in TSS or TiA of fruits by the effect of any treatments. Interestingly, UV-C irradiation induced greater antioxidant properties of blueberries. Bluegold and Brigitta fruits revealed increased RSA under 4.6 kJ m?2 doses. Also, Bluegold showed the highest levels of TPC at doses of 4.6 kJ m?2 of UV-C. Moreover, fruits of all cultivars exhibited increased TCA in response to the higher doses of UV-C. UV-C irradiation could be an interesting tool to improve antioxidant potential in highbush blueberries, which can negatively affect fruit quality for fresh consumption. © 2020 Elsevier B.V., All rights reserved.

ABSTRACT The native conifer lleuque (Prumnopitys andina (Poepp. ex Endl.) de Laub.) grows in southern Chile, and has an edible and fleshy ovoid fruit. Some species of the genus Prumnopitys are valuable for the medicinal value of their edible fruits. Thus, the aim of this research was to characterize the phytochemical and antioxidant compounds in four ripening stages of P. andina fruits from La Araucanía Region, Chile. Fruit quality related parameters, bromatological, antioxidant and phenolic compounds analyses were performed in order to highlight their potential for human consumption. Our study showed that fresh weight, equatorial diameter, and soluble solid content significantly increased (P < 0.05) in P. andina fruits during ripening, reaching 4.02 ± 0.2 g, 17.9 ± 0.6 mm, and 23.7 ± 0.5 °Brix, respectively, per fruit at stage IV. Our bromatological analyses showed that P. andina fruits had 1.17 ± 0.1 g 100 g-1 DW protein, 1.55 ± 0.2 g 100 g-1 DW crude fiber, and 10.76 ± 2.2 g 100 g-1 DW fruit of ash at fruit ripe. Likewise, we found 2.6 ± 0.2 mg g-1 FW total phenols, 2.2 ± 0.2 mg trolox equivalent g-1 FW of antioxidant activity, and 6.4 ± 0.2 mg rutin equivalent g-1 FW total flavonoid in P. andina fruits. Interestingly, ripening stages I and II showed higher antioxidant compound levels compared to stages III and IV, with the exception of total anthocyanins, which did not change throughout the ripening process. This study shows that P. andina has great potential as a fruit with significant functional properties, which could help promote the propagation, care, and use of this native conifer.

Citrus are a globally important fruit crop. Abiotic stressors such as drought and salinity adversely affect physiological citrus performance and survival. With the aim of improving drought tolerance in citrus plants, we constructed transgenic lines of Citrus lemon overexpressing the Arabidopsis transcription factor CBF3. Molecular, physiological, and quantitative real-time analyses showed high expression of AtCBF3 in three selected transgenic lines. During a 15-day treatment of water deficit by cessation of irrigation, the transgenic lines LM2 and LM14 showed lower stomatal conductance and transpiration paired with lower photosynthesis, whereas transgenic line LM7 maintained its photosynthesis, declining stomatal conductance, and transpiration compared to WT plants, which is manifested into more efficient water use. The genes Cs RafS1 and CsGolS1 showed similar or greater expression in one of the transgenic lines with respect to control plants. Moreover, transgenic lines were more tolerant to saline stress and presented a greener phenotype with increased chlorophyll content in leaf discs compared to WT plants. In addition, a lower electrical conductivity in solution was observed in transgenic lines. Furthermore, all transgenic lines exhibited significantly less accumulation of reactive oxygen species than WT plants. Together, these results suggest the potential for heterologous expression of the AtCBF3 gene to mediate tolerance to hydric and saline stress in citrus plants.

Stomatal closure is a common adaptation response of plants to the onset of drought condition and its regulation is controlled by transcription factors. MYB60 , a transcription factor involved in the regulation of light-induced stomatal opening, has been characterized in arabidopsis and grapevine. In this work, we studied the role of MYB60 homolog SIMYB60 in tomato plants. We identified, isolated, and sequenced the SIMYB60 coding sequence, and found domains and motifs characteristic of other MYB60 proteins. We determined that SlMYB60 is mainly expressed in leaves, and its expression is repressed by abscisic acid. Next, we isolated a putative promoter region containing regulatory elements responsible for guard cell expression and other putative regulatory elements related to ABA repression and vascular tissue expression. Protein localization assays demonstrated that SlMYB60 localizes to the nucleus. Finally, SlMYB60 is able to complement the mutant phenotype of atmyb60-1 in Arabidopsis. Together, these results indicate that SlMYB60 is the homologous gene in tomato and potentially offer a molecular target to improve crops.

Fil: Roldan, Cecilia Soledad. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina