Selenium Biofortification of Soybean Seeds Influences Physiological Responses of Seedlings to Osmotic Stress.

Climate change poses a serious threat to agricultural production. Water deficit in agricultural soils is one of the consequences of climate change that has a negative impact on crop growth and yield. Selenium (Se) is known to be involved in plant defense against biotic and abiotic stress through metabolic, structural, and physiological activity in higher plants. The aim of this study was to investigate the physiological response of Se-biofortified soybean (Glycine max (L.) Merrill) seedlings under osmotic stress. For this research, we used biofortified soybean grain obtained after foliar Se biofortification in 2020. The experiment was conducted in a growth chamber with two cultivars (Lucija and Sonja) grown on filter paper in three replicates. The experiment was carried out with two watering treatments: distilled water (PEG-0) and 2.5% polyethylene glycol 6000 (PEG-2.5) on Se-biofortified seeds (Se) and nonbiofortified seeds (wSe). Contents of lipid peroxidation product (LP), free proline (PRO), total phenolic content (TP), ferric reducing antioxidant power (FRAP), and ascorbic acid (AA) were analyzed in 7-days-old seedlings. Significant differences were detected in the Se content of soybean grains between the two cultivars. A milder reaction to PEG-2.5 was observed in cultivar Lucija in both Se and wSe treatments, which might represent the mitigating effects of Se on osmotic stress in this cultivar. Contrarily, in cultivar Sonja, Se adversely affected all analyzed traits in the PEG-2.5 treatment. Ultimately, Se is a pro-oxidant in Sonja, whereas it represents an anti-oxidant in Lucija. In conclusion, different soybean cultivars show contrasting physiological reactions to both osmotic stress and Se. However, the activation of antioxidant pathways in Sonja can also be interpreted as added value in soybean seedlings as a functional food.

Assessment of the influence of different sample processing and cold storage duration on plant free proline content analyses.

INTRODUCTION: A method which is widely accepted for the analysis of free proline content in plant tissues is based on the use of 3% sulfosalicylic acid as an extractant, followed by spectrophotometric quantification of a proline-ninhydrin complex in toluene. However, sample preparation and storage may influence the proline actually measured. This may give misleading or difficult to compare data. OBJECTIVE AND METHODOLOGY: To evaluate free proline levels fresh and frozen strawberry (Fragaria × ananassa Duch.) leaves and soybean [Glycine max (L.) Merr.] hypocotyl tissues were used. These were ground with or without liquid nitrogen and proline extracted with sulfosalicylic acid. A particular focus was the influence of plant sample cold storage duration (1, 4 and 12 weeks at -20°C) on tissue proline levels measured. RESULTS: The free proline content analyses, carried out in leaves of Fragaria × ananassa Duch. as well as in hypocotyls of Glycine max (L.) Merr., showed a significant influence of the sample preparation method and cold storage period. Long-term storage of up to 12 weeks at -20°C led to a significant increase in the measured proline in all samples analysed. CONCLUSION: The observed changes in proline content in plant tissue samples stored at -20°C indicate the likelihood of the over-estimation of the proline content if the proline analyses are delayed. Plant sample processing and cold storage duration seem to have an important influence on results of proline analyses. Therefore it is recommended that samples should be ground fresh and analysed immediately.

Validation of flavonoids as potential dipeptidyl peptidase III inhibitors: Experimental and computational approach.

Fifteen flavonoids were studied for their inhibitory activity against human dipeptidyl peptidase III (hDPP III) combining an in vitro assay with an in silico molecular modeling study. All analyzed flavonoids showed inhibitory effects against hDPP III with the IC50 values ranging from 22.0 to 437.2 µm. Our 3D QSAR studies indicate that the presence of hydrophilic regions at a flavonoid molecule increases its inhibitory activity, while the higher percentage of hydrophobic surfaces has negative impact on enzyme inhibition. Furthermore, molecular dynamics (MD) simulations of the complex of hDPP III with one of the most potent inhibitors, luteolin, were performed, and binding mode analysis revealed that the 3' and 4' hydroxyl group on B-ring as well as 5 and 7 hydroxyl group on A-ring helps luteolin to interact with the Asn391, Asn406, Tyr417, His450, Glu451, Val447, Glu512, Asn545, Gln566, and Arg572 residues. The MD results clearly provide valuable information explaining the importance of flavonoid hydroxyl groups in the mechanism for the binding pattern at the active site of hDPP III.

The relationship of proline content and metabolism on the productivity of maize plants.

The free proline content in maize ear-leaves, silk and pollen were analyzed in field grown plants which had matured to the pollination stage. Using maize hybrids PR34F02, PR35P12 and PR36B08 field trials were set up at two locations in eastern Croatia in two different years. Two enzymes of proline metabolism were analyzed in the same leaf samples and specific activities of synthetase (P5CS) and proline dehydrogenase (PDH). Plant productivity was evaluated at harvest by the estimation of total and fully developed grain number per ear and per plant, the mean single grain mass, and the mass of grain per plant. The year in which the plants were grown had a very significant effect on the free proline content in the leaf and pollen, as well as on the enzyme activities assayed. The differences between the plants from the two localities were very significant in all tested parameters of plant grain productivity. There was a significant genotype effect on proline content and P5CS total activity in leaf and on all the productivity parameters. Some of the correlations established suggest that the rate of proline synthesis and degradation in maize ear-leaf at pollination might contribute to the final grain production of the maize plant. Multiple regression analyses was used to further analyze the relationship between proline and grain productivity, but it is clear that future work should include other environmental conditions, plant species and organs such as roots.