Differences in Organic Solute and Metabolites of Leymus chinensis in Response to Different Intensities of Salt and Alkali Stress

The Involvement of Amino Acid Metabolism in the Mechanisms of Salt Tolerance Adaptation in Medicago sativa and Medicago truncatula

Amino acid metabolism constitutes a major metabolic pathway in plants, playing an important role in the modulation of plant responses to stress. In this study, we investigated the amino acid metabolism responses of M. sativa (Medicago sativa L.) and M. truncatula (Medicago truncatula L.) plants under salt stress using transcriptomic and proteomic approaches to elucidate their salt stress tolerance mechanisms in relation to the regulation of amino acid homeostasis. Transcriptome and proteome sequencing followed by Kyoto Gene and Genome Encyclopedia enrichment analysis revealed 34 differentially expressed genes and 45 differentially expressed proteins involved in valine, leucine, and isoleucine degradation, tyrosine metabolism, and glutathione metabolism. Significant differences were observed in the expression of glutathione S-transferase (GST) within the glutathione metabolic pathway between M. sativa and M. truncatula. The induction of valine, leucine, and isoleucine metabolism, aldehyde dehydrogenases (ALDHs), and alanine-glyoxylate aminotransferases (AGXTs), involved in intracellular reactive oxygen species scavenging, also significantly differed under salt stress. Significant differences were identified in the expression of tyrosine decarboxylases (TDCs) involved in tyrosine metabolism, which are responsible for tyramine biosynthesis and can enhance plant tolerance to salt stress. This study delved into the effects of amino acid metabolism on the salt tolerance mechanisms of M. sativa and M. truncatula, which is crucial in guiding the future breeding of salt-tolerant alfalfa varieties.

Correlation between microbial communities and flavor compounds in Suantangzi dough from Liaoning Province, China

Suantangzi is a fermented corn food product with Manchu characteristics from Liaoning Province, China. To analyze the microbial diversity and flavor compounds in Suantangzi dough, this study utilized high-throughput sequencing of the 16S rRNA and internal transcribed spacer regions, high-performance liquid chromatography, and gas chromatography time-of-flight mass spectrometry. Spearman correlation analysis and random forest model were conducted to investigate the correlation between the dominant genera and flavor compounds. A total of 267 and 123 bacterial and fungal genera, respectively, were identified. Flavor compound analysis identified 7 and 156 organic acids and other flavor compounds, respectively, and partial least squares discriminant analysis was used to screen 22 differential flavor compounds. Additionally, Paucilactobacillus, Pediococcus, and Tausonia genera were speculated to produce different flavors in Suantangzi dough made in different regions. These findings provide a theoretical foundation for microbial community dynamics and the formation of key flavor compounds in Suantangzi dough.

Effects of saline-alkali stress on cotton growth and physiochemical expression with cascading effects on aphid abundance

Introduction

Environmental stresses, such as soil salinity or alkalinity, usually affect crop growth and secondary plant metabolism, with follow on effects on foliar-feeding insects. Nevertheless, the underlying mechanism of how saline-alkali stress affects the key cotton pest Aphis gossypii Glover is poorly understood.

Methods

In this study, we first considered effects of three types of saline-alkali stress (i.e., salinity alone, alkalinity alone - both at different concentration - and their mixed effects) on cotton plants. We then measured impacts of stress on (1) above and below plant growth traits (e.g., plant height, leaf area, root volume), (2) levels of nutrients and secondary metabolites in cotton leaves, and (3) feeding behavior, life-table parameters, and population growth of A. gossypii. We then used a path analysis to evaluate cascading effects of changes in plant growth (due to stress) and changes in levels of nutrients or secondary metabolites on growth of individual cotton aphids and aphid populations.

Results

We found either salinity or alkalinity stresses significantly reduced cotton growth, increased the content of tannin, soluble sugars, and proline in the leaves, and suppressed aphid growth and development, (including longevity, fecundity, and intrinsic rate of increase) and aphid population growth. Alkalinity had stronger effects on these traits than did salinity.

Discussion

This work provides insights into the bottom-up interaction mechanism by which these environmental stresses mediate aphid infestation levels in the cotton agricultural ecosystem.

Alleviation of cotton growth suppression caused by salinity through biochar is strongly linked to the microbial metabolic potential in saline-alkali soil

Biochar is a typical soil organic amendment; however, there is limited understanding of its impact on the metabolic characteristics of microorganisms in saline-alkaline soil microenvironment, as well as the advantages and disadvantages of plant-microorganism interactions. To elucidate the mechanisms underlying the impact of saline-alkali stress on cotton, a 6-month pot experiment was conducted, involving the sowing of cotton seedlings in saline-alkali soil. Three different biochar application levels were established: 0 % (C0), 1 % (C1), and 2 % (C2). Results indicated that biochar addition improved the biomass of cotton plants, especially under C2 treatment; the dry weight of cotton bolls were 8.15 times that of C0. Biochar application led to a rise in the accumulation of photosynthetic pigments by 8.30-51.89 % and carbohydrates by 7.4-10.7 times, respectively. Moreover, peroxidase (POD) activity, the content of glutathione (GSH), and ascorbic acid (ASA) were elevated by 23.97 %, 118.39 %, and 48.30 % under C2 treatment, respectively. Biochar caused a reduction in Na+ uptake by 8.21-39.47 %, relative electrical conductivity (REC) of plants, and improved K+/Na+ and Ca2+/Na+ ratio indicating that biochar alleviated salinity-caused growth reduction. Additionally, the application of biochar enhanced the absorption intensity of polysaccharide fingerprints in cotton leaves and roots. Two-factor co-occurrence analysis indicated that the key differential metabolites connected to several metabolic pathways were L-phenylalanine, piperidine, L-tryptophan, and allysine. Interestingly, biochar altered the metabolic characteristics of saline-alkali soil, especially related to the biosynthesis and metabolism of amino acids and purine metabolism. In conclusion, this study demonstrates that biochar may be advantageous in saline soil microenvironment; it has a favorable impact on how plants and soil microbial metabolism interact.

Carboxylic acid accumulation and secretion contribute to the alkali-stress tolerance of halophyte Leymus chinensis

Leymus chinensis is a dominant halophytic grass in alkalized grasslands of Northeast China. To explore the alkali-tolerance mechanism of L. chinensis, we applied a widely targeted metabolomic approach to analyze metabolic responses of its root exudates, root tissues and leaves under alkali-stress conditions. L. chinensis extensively secreted organic acids, phenolic acids, free fatty acids and other substances having -COOH or phosphate groups when grown under alkali-stress conditions. The buffering capacity of these secreted substances promoted pH regulation in the rhizosphere during responses to alkali stress. L. chinensis leaves exhibited enhanced accumulations of free fatty acids, lipids, amino acids, organic acids, phenolic acids and alkaloids, which play important roles in maintaining cell membrane stability, regulating osmotic pressure and providing substrates for the alkali-stress responses of roots. The accumulations of numerous flavonoids, saccharides and alcohols were extensively enhanced in the roots of L. chinensis, but rarely enhanced in the leaves, under alkali-stress conditions. Enhanced accumulations of flavonoids, saccharides and alcohols increased the removal of reactive oxygen species and alleviated oxygen damage caused by alkali stress. In this study, we revealed the metabolic response mechanisms of L. chinensis under alkali-stress conditions, emphasizing important roles for the accumulation and secretion of organic acids, amino acids, fatty acids and other substances in alkali tolerance.

Growth, Physiology and Nutritional Quality of C4 Halophyte Portulaca oleracea L. Grown Aeroponically in Different Percentages of Artificial Seawater under Different Light-Emitting Diode Spectral Qualities

Edible halophyte Portulaca oleracea L., known as purslane, was grown in two percentages of artificial seawater (ASW) under two combined red (R) and blue (B) LED spectra. High salinity (40% ASW) negatively affected shoot productivity and leaf growth of purslane compared to those grown in 10% ASW. Photosynthetic pigment and total reduced nitrogen concentrations were significantly higher in purslane grown in 10% ASW than in 40% ASW. However, LED spectral quality did not markedly influence these parameters. Grown in 10% ASW under R/B 2.2, purslane had the highest maximum nitrate reductase activity, while those in 40% ASW under R/B 2.2 had the highest activation state. Under both light qualities, purslane had a sevenfold increase in proline concentration in 40% ASW than in 10% ASW. Total phenolic compounds' concentration was the highest in 10% ASW under R/B 0.9, while there were no significant differences in the accumulation of total soluble sugars and ascorbic acids among all plants. Antioxidant enzymes activities were lower in 40% ASW under R/B 2.2 compared to the other conditions. In conclusion, salinity affected the yield, physiology and nutritional quality of purslane. The impacts of LED spectral quality on purslane were only reflected by certain physiological and nutritional parameters.