Carbohydrate Accumulation and Differential Transcript Expression in Winter Wheat Lines with Different Levels of Snow Mold and Freezing Tolerance after Cold Treatment

Multiomic analysis reveals that the flavonoid biosynthesis pathway is associated with cold tolerance in Heracleum moellendorffii Hance

Heracleum moellendorffii Hance is a perennial herbaceous plant that is adaptable to cold environments and has both edible and medicinal value. Given that no reference genome for this species is available, we constructed a high-quality transcript isoform library using full-length transcriptome sequencing and conducted a comparative genomic analysis. Samples were obtained from plants that had been subjected to cold stress for 12, 24 and 36 hours (Cold_12, Cold_24, and Cold_36, respectively) and from control plants (Cold_0) that were not subjected to cold stress and used in transcriptome and nontargeted metabolome analyses. Compared with the genes expressed in CK (Cold_0), the number of differentially expressed genes (DEGs) in Cold 12, Cold_24, and Cold_36 increased gradually over time; plants subjected to 12, 24 and 36 hours of cold stress displayed 669, 6084, and 24,129 DEGs, respectively. The DEGs were clustered into 8 subclasses by k-means clustering; subclasses 2, 3, 4, and 7 were enriched in pathways related to "flavonoid biosynthesis". Nontargeted metabolome analysis revealed that 3719 annotated metabolites were shared by all four groups of samples. We identified 1186, 1087, and 1097 differentially accumulated metabolites (DAMs) in three comparisons: Cold_12 vs. CK, Cold_24 vs. CK, and Cold_36 vs. CK, respectively. The DAMs were predominantly enriched in the "flavonoid biosynthesis pathway". Through WGCNA, we obtained five modules and 29 flavonoid-related metabolites with extremely significant module-metabolite paired relationships (|correlation coefficient|> 0.9, P < 0.01). We analysed the DEGs and DAMs of the flavonoid biosynthetic pathway in H. moellendorffii Hance under cold stress and constructed a correlation network between transcription factors (TFs) and structural genes in the pathway. RT-qPCR was used to confirm the expression of four hub genes from the WGCNA, six TFs, and 15 structural genes of the flavonoid biosynthetic pathway. These data provide a foundation for functional genomics studies of H. moellendorffii Hance and contribute to the study of the molecular mechanisms and transcriptional regulation of flavonoid accumulation by TFs under cold stress conditions in plants.

Advances and opportunities in unraveling cold-tolerance mechanisms in the world's primary staple food crops

Temperatures below or above optimal growth conditions are among the major stressors affecting productivity, end-use quality, and distribution of key staple crops including rice (Oryza sativa), wheat (Triticum aestivum), and maize (Zea mays L.). Among temperature stresses, cold stress induces cellular changes that cause oxidative stress and slowdown metabolism, limit growth, and ultimately reduce crop productivity. Perception of cold stress by plant cells leads to the activation of cold-responsive transcription factors and downstream genes, which ultimately impart cold tolerance. The response triggered in crops to cold stress includes gene expression/suppression, the accumulation of sugars upon chilling, and signaling molecules, among others. Much of the information on the effects of cold stress on perception, signal transduction, gene expression, and plant metabolism are available in the model plant Arabidopsis but somewhat lacking in major crops. Hence, a complete understanding of the molecular mechanisms by which staple crops respond to cold stress remain largely unknown. Here, we make an effort to elaborate on the molecular mechanisms employed in response to low-temperature stress. We summarize the effects of cold stress on the growth and development of these crops, the mechanism of cold perception, and the role of various sensors and transducers in cold signaling. We discuss the progress in cold tolerance research at the genome, transcriptome, proteome, and metabolome levels and highlight how these findings provide opportunities for designing cold-tolerant crops for the future.

Chemical Composition, Antibacterial and Antifungal Activity of the Essential Oil from Cistus ladanifer L

Cistus ladanifer L. is a plant widely used in folk medicine to treat various illnesses. This study aims to evaluate the effect of the plant flourishing time harvest on the chemical composition and the antimicrobial effect of its essential oil. Chemical analysis of the essential oil was carried out using gas chromatography-mass spectrometry (GC-MS). The antibacterial and antifungal proprieties were tested against four selected bacteria (Staphylococcus aureus, Salmonella Typhi, Escherichia coli, and Acinetobacter baumannii) and nine fungi (Yeasts (Candida tropicalis, Candida glabrata, Candida dubliniensis, Candida sp., Rhodotorula rubra, Cryptococcus neoformans) and molds (Penicillium sp. (P), Fusarium sp. (F), Aspergillus niger (A. niger)), respectively. The essential oil of C. ladanifer demonstrated a powerful antibacterial activity with an inhibition zone of 55 ± 0.22 mm for Staphylococcus aureus, 42 ± 0.11 mm for Escherichia coli, 35 ± 0.27 mm for Acinetobacter baumannii (Full resistant to antibiotics) and 30 ± 0.25 mm for Salmonella Typhi. It also inhibited all tested bacteria at 10 µL/mL. For the antifungal activity test, C. tropicalis and C. neoformans appeared to be the most sensitive strains to the essential oil with an inhibition zone of 13 mm, followed by R. rubra and Penicillium sp. (12 mm), then C. dubliniensis and C. glabrata (11 mm). The chemical analysis of the essential oil by GC-MS revealed that the major components of the essential oil were viridiflorol (17.64%), pinocarveol (11.02%), bornylacetate (9.38%), and ledol (8.85%). C. ladanifer exhibited a remarkable antimicrobial activity that could be more exploited to develop targeted natural remedies against specific diseases.

Fructan Structure and Metabolism in Overwintering Plants

In northern regions, annual and perennial overwintering plants such as wheat and temperate grasses accumulate fructan in vegetative tissues as an energy source. This is necessary for the survival of wintering tissues and degrading fructan for regeneration in spring. Other types of wintering plants, including chicory and asparagus, store fructan as a reserve carbohydrate in their roots during winter for shoot- and spear-sprouting in spring. In this review, fructan metabolism in plants during winter is discussed, with a focus on the fructan-degrading enzyme, fructan exohydrolase (FEH). Plant fructan synthase genes were isolated in the 2000s, and FEH genes have been isolated since the cloning of synthase genes. There are many types of FEH in plants with complex-structured fructan, and these FEHs control various kinds of fructan metabolism in growth and survival by different physiological responses. The results of recent studies on the fructan metabolism of plants in winter have shown that changes in fructan contents in wintering plants that are involved in freezing tolerance and snow mold resistance might be largely controlled by regulation of the expressions of genes for fructan synthesis, whereas fructan degradation by FEHs is related to constant energy consumption for survival during winter and rapid sugar supply for regeneration or sprouting of tissues in spring.