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Fil: Vargas Gil, Silvina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Fisiología y Recursos Geneticos Vegetales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Plants co-ordinate information derived from many diverse external and internal signals to ensure appropriate control of gene expression under optimal and stress conditions. In this work, the relationships between catalase (CAT) and H₂O₂ during drought in wheat (Triticum aestivum L.) are studied. Drought-induced H₂O₂ accumulation correlated with decreases in soil water content and CO₂ assimilation. Leaf H₂O₂ content increased even though total CAT activity doubled under severe drought conditions. Diurnal regulation of CAT1 and CAT2 mRNA abundance was apparent in all conditions and day/night CAT1 and CAT2 expression patterns were modified by mild and severe drought. The abundance of CAT1 transcripts was regulated by circadian controls that persisted in continuous darkness, while CAT2 was modulated by light. Drought decreased abundance, and modified the pattern, of CAT1 and CAT2 mRNAs. It was concluded that the complex regulation of CAT mRNA, particularly at the level of translation, allows precise control of leaf H₂O₂ accumulation.

Prosopis alba Griseb. (algarrobo blanco) is an important tree legume in semiarid regions of South America. Under field conditions, their seedlings are subjected to a wide range of environmental conditions that might produce stress, reducing their survival and/or growth. The aim of this work was to evaluate the combined effect of two native arbuscular mycorrhizal fungi (AMF) inocula and fertilization on growth variables of P. alba seedlings under nursery conditions and after drought stress. P. alba seedlings received different levels of basic fertilization (0%, 25% and 100%) and were inoculated with native AMF isolated from different rainfall regions of Parque Chaqueño Argentino: Colonia Benítez (CB, 1300 mm rainfall) and Padre Lozano (PL, 650 mm rainfall) or a mixture of both inocula (MIX), while the control group remained uninoculated. The combined application of native AMF and fertilization did not affect mycorrhizal colonization but allowed the formation of the different AMF structures. Moreover, when comparing the PL inoculum from a low rainfall region with other treatments, it significantly increased growth and development under nursery conditions and drought stress tolerance in the greenhouse. Therefore, AMF benefits for P. alba were related to inoculum source, being improved by the application of low fertilizer rates. This work supports the development of sustainable P. alba seedlings production and their field establishment under symbiotic conditions with native AMF.

In this work, we described an system adequate for investigating the pathosystem soybean/arbuscular mycorrhizal fungi (AMF)/ Pre-mycorrhized plantlets with were infected by either locally via a plug of gel supporting mycelium (Method 1) or via a macroconidia suspension applied to the medium surface (Method 2). Root colonization by the AMF and infection by the pathogen were similar to the usual observations in pot experiments. Within a period of 18 days, more than 20% of the roots were colonized by the AMF and infection by the pathogen was observed in all the plants. In presence of AMF, a decrease in symptoms and in the level of root tissue infection was noticed. With Method 1, smaller necrotic lesions were observed in the pre-mycorrhized plantlets. In Method 2, pathogen infection was slower but more homogenous. These results demonstrated the suitability of the cultivation system to study the pathosystem soybean/AMF/ . We propose this cultivation system for studying the mechanisms involved in the biocontrol conferred by AMF against in soybean.

Water stress is one of the most important environmental factors that regulate a plant's growth and development. In agronomic practice the effects of water stress are translated into low yield and/or reduced quality. Abscisic acid (ABA) sprays (1 mM) were applied to wheat plants at different phenological stages and the effects on several physiological variables and on yield were evaluated under field conditions at different water regimes. Studies were conducted in the field across three consecutive winter-spring seasons. ABA treatments were applied at the beginning of shoot enlargement and repeated at anthesis. Exogenous ABA increased shoot dry weight and maintained a high concentration of photosynthetic pigments for a longer period of time during grain growth and maturation. Although ABA applications increased stomatal closure immediately after its application, the longer-term effect was to allow for a greater ostiolar opening of the stomatal pore which resulted in increased conductance of gases and water vapor. ABA also improved the transport of photoassimilates from the leaves and stem to the developing grains, that is, it effectively increased the sink strength of the grains. This correlated with a yield increase without significantly changing the protein quality in the grains. Thus, elevated ABA levels from exogenous application or genetic selection could help improve agricultural production of grains in arid areas where irrigation is not possible.

Hieronymiella peruviana, a recently described endemic species from southern Peru, belongs to the Amaryllidaceae family and is known for its diversity of alkaloids. Amaryllidoideae have been studied for their diverse biological activities, particularly for their properties in treating neurodegenerative diseases. This work examines the alkaloidal profile using GC-MS and UPLC-MS/MS of alkaloid-enriched extracts obtained from the leaves and bulbs of H. peruviana and their inhibitory activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. In addition, the phenolic and flavonoid content in the methanolic extract from bulbs was quantified and the antioxidant capacity was evaluated. Moreover, the seed germination was investigated under four temperature conditions (15, 20, 25, and 30 °C). Twenty-two alkaloids, most of them of the homolycorine- and galanthamine-type, including galanthamine, were identified in the alkaloid extracts by means of GC-MS and UPLC-MS/MS analysis. Lycorine and 8-O-Demethylhomolycorine were the most abundant alkaloids in the bulbs and leaves, respectively. The leaves and bulbs alkaloid extracts demonstrated strong AChE inhibition (IC50 = 5.20–8.60 µg/mL) and moderate BuChE inhibition (IC50 = 90.20–122.76 µg/mL). The bulbs’ methanolic extract exhibited mild antioxidant activity, showing 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) values of 16.36% at 500 μg/mL and 58.31 mg Trolox equivalents (TE)/g, respectively. Seed germination was most effective at 20 °C and 25 °C. Finally, 60 days after germination, the survival rate of H. peruviana seedlings was 48.33%. These findings establish H. peruviana as a promising source of bioactive alkaloids with potential pharmacological and therapeutic applications, as well as providing critical insights for its propagation and conservation.

The Amaryllidaceae family represents a prolific source of pharmacologically active compounds, boasting over 700 diverse alkaloids identified to date. However, the genus Eustephia (Amaryllidoideae subfamily) remains largely unexplored. This study focused on the alkaloid profiles and pharmacological potential of bulb and leaves extracts from three Peruvian Eustephia species (E. coccinea, E. darwinii, and E. hugoei). The phenolic and flavonoid levels as well as the antioxidant activity of the methanolic extracts, were determined. Twenty-six alkaloids were identified in the alkaloid-enriched extracts (AEEs). Homolycorine-type alkaloids predominated in E. darwinii and E. hugoei, whereas E. coccinea displayed greater chemical diversity showing assoanine as the main detected alkaloid. In addition, candimine was widely distributed across species. AEEs showed stronger enzyme inhibition of acetylcholinesterase (AChE) compared to butyrylcholinesterase (BuChE). Notably, the AEE from E. coccinea leaves showed the highest AChE inhibition (IC50 = 1.82 μg/mL), while the AEE from bulbs exhibited the strongest BuChE inhibitory activity (IC50 = 61.22 μg/mL). Regarding anti-T. cruzi effect, the E. darwinii bulbs AEE was most potent and selective against amastigote forms (IC50 = 2.1 μg/mL; SI = 8.83). These findings underscore the potential of Peruvian Eustephia species as promising sources of pharmacologically relevant alkaloids, with possible applications in neurodegenerative disorders and Chagas disease.

Sunflower chlorotic mottle virus (SuCMoV) is a recently described potyvirus that causes systemic infections in sunflower plants leading to chlorotic mottling and important growth reductions and yield losses. Oxidative damage is expressed after symptom development in this host-pathogen combination. The involvement of antioxidant enzyme activities in disease susceptibility was studied in two sunflower lines differing in the intensity and rate of development of SuCMoV infections: L2 is more susceptible than L33. A transient superoxide production peak was detected in leaves of both lines before symptom development. H2O2 accumulation increased before symptom expression in infected plants of L33 but in L2 such increase was registered only after symptoms became evident. In healthy plants of both lines, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) showed similar activity levels. In inoculated plants of line L2, but not in L33, SOD and CAT activities increased significantly before the appearance of symptoms, and APX increases were detected later. A 1 mM SA treatment effectively decreased SuCMoV accumulation in plants of L2 but it did not affect it in L33. This treatment increased H2O2 accumulation and prevented the increase in antioxidant enzyme activities in infected plants of L2. It is suggested that increases in antioxidant enzyme activities interrupted the signals generated by the increase in ROS, which may have otherwise triggered defence reactions in the host and thus, resulted in a compatible interaction.

Modern breeding programs have reduced genetic variability and might have caused a reduction in plant colonization by arbuscular mycorrhizal fungi (AM). In our previous studies, mycorrhizal colonization was affected in improved soybean genotypes, mainly arbuscule formation. Despite substantial knowledge of the symbiosis-related changes of the transcriptome and proteome, only sparse clues regarding metabolite alterations are available. Here, we evaluated metabolite changes between improved (I-1) and unimproved (UI-4) soybean genotypes and also compare their metabolic responses after AM root colonization. Soybean genotypes inoculated or not with AM were grown in a chamber under controlled light and temperature conditions. At 20 days after inoculation, we evaluated soluble metabolites of each genotype and treatment measured by GC-MS. In this analysis, when comparing non-AM roots between genotypes, I-1 had a lower amount of 31 and higher amount of only 4 metabolites than the UI-4 genotype. When comparing AM roots, I-1 had a lower amount of 36 and higher amount of 4 metabolites than UI-4 (different to those found altered in non-AM treated plants). Lastly, comparing the AM vs non-AM treatments, I-1 had increased levels of three and reduced levels of 24 metabolites, while UI-4 only had levels of 12 metabolites reduced by the effect of mycorrhizas. We found the major changes in sugars, polyols, amino acids, and carboxylic acids. In a targeted analysis, we found lower levels of isoflavonoids and alpha-tocopherol and higher levels of malondialdehyde in the I-1 genotype that can affect soybean-AM symbiosis. Our studies have the potential to support improving soybean with a greater capacity to be colonized and responsive to AM interaction.

Fil: Luna, Celina Mercedes. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; Argentina