Comparative analysis of drought stress-induced physiological and transcriptional changes of two black sesame cultivars during anthesis

Genome-wide identification and expression analysis of the lipoxygenase gene family in sesame reveals regulatory networks in response to abiotic stress

BACKGROUND

Plant lipoxygenase (Lox) genes, catalyze polyunsaturated fatty acids and play essential roles in plant growth, development, and stress responses. It is extensively studied under various stresses, their role in abiotic stress responses remains unexplored in sesame.

METHODS AND RESULTS

This study identified seven Lox genes in sesame divided into two subfamilies: 9-Lox (Silox1, Silox2 and Silox3) are likely involved in pathogen defence and signalling and 13-Lox (Type-I: Silox4 and Type-II: Silox5, Silox6 and Silox7) play crucial roles in jasmonic acid biosynthesis and abiotic stress responses. Silox genes have undergone purifying selection, promoting the stability of gene function and prefer codons with A or T in the third position. The chromosomal distribution, sequence similarity, and subcellular localization, with conserved lipoxygenase domains and motifs were analysed. Promoter regions contained 34 cis-acting regulatory elements (e.g. WRKY, ERF, and bHLH) and 35 transcription factors binding sites (TFBS) linked to light, stress (e.g. MYC, W-box, ERE and STRE), phytohormones, and growth. Differential Gene Expression (DGE) analysis showed Lox1 was upregulated in Drought sensitive (DS) and in Drought tolerant (DT) the Lox1 & Lox3 were upregulated when compared to control. In addition, weighted gene co-expression network analysis (WGCNA) of Lox, showed that blue module is positively correlated with drought tolerance. Fourteen hub genes related to stress were identified, which closely associated with Lox1. Gene ontology and KEGG pathway analyses showed that these genes were linked to linoleic acid metabolism, lipid metabolism, and stress response. Quantitative Real-Time PCR (qRT-PCR) analysis confirmed that Silox genes showed time-varying differential expression under drought, salt and a combined drought-salt stress treatments.

CONCLUSION

This research lays the groundwork for future studies on the role of Lox genes in sesame's growth and stress adaptation.

Integrative transcriptome and metabolome analysis reveals the mechanism of fulvic acid alleviating drought stress in oat

Drought stress inhibits oat growth and yield. The application of fulvic acid (FA) can improve the drought resistance of oats, but the corresponding molecular mechanism of FA-mediated drought resistance remains unclear. Here, we studied the effects of FA on the drought tolerance of oat leaves through physiological, transcriptomic, and metabolomics analyses, and identified FA-induced genes and metabolites related to drought tolerance. Physiological analysis showed that under drought stress, FA increased the relative water and chlorophyll contents of oat leaves, enhanced the activity of antioxidant enzymes (SOD, POD, PAL, CAT and 4CL), inhibited the accumulation of malondialdehyde (MDA), hydrogen peroxide (H2O2) and dehydroascorbic acid (DHA), reduced the degree of oxidative damage in oat leaves, improved the drought resistance of oats, and promoted the growth of oat plants. Transcriptome and metabolite analyses revealed 652 differentially expressed genes (DEGs) and 571 differentially expressed metabolites (DEMs) in FA-treated oat leaves under drought stress. These DEGs and DEMs are involved in a variety of biological processes, such as phenylspropanoid biosynthesis and glutathione metabolism pathways. Additionally, FA may be involved in regulating the role of DEGs and DEMs in phenylpropanoid biosynthesis and glutathione metabolism under drought stress. In conclusion, our results suggest that FA promotes oat growth under drought stress by attenuating membrane lipid peroxidation and regulating the antioxidant system, phenylpropanoid biosynthesis, and glutathione metabolism pathways in oat leaves. This study provides new insights into the complex mechanisms by which FA improves drought tolerance in crops.

Integrated analysis of transcriptomics and metabolomics of garden asparagus (Asparagus officinalis L.) under drought stress

BACKGROUND

Drought is a leading environmental factor affecting plant growth. To explore the drought tolerance mechanism of asparagus, this study analyzed the responses of two asparagus varieties, namely, 'Jilv3' (drought tolerant) and 'Pacific Early' (drought sensitive), to drought stress using metabolomics and transcriptomics.

RESULTS

In total, 2,567 and 7,187 differentially expressed genes (DEGs) were identified in 'Pacific Early' and 'Jilv3', respectively, by comparing the transcriptome expression patterns between the normal watering treatment and the drought stress treatment. These DEGs were significantly enriched in the amino acid biosynthesis, carbon metabolism, phenylpropanoid biosynthesis, and plant hormone signal transduction pathways. In 'Jilv3', DEGs were also enriched in the following energy metabolism-related pathways: citrate cycle (TCA cycle), glycolysis/gluconeogenesis, and pyruvate metabolism. This study also identified 112 and 254 differentially accumulated metabolites (DAMs) in 'Pacific Early' and 'Jilv3' under drought stress compared with normal watering, respectively. The amino acid, flavonoid, organic acid, and soluble sugar contents were more significantly enhanced in 'Jilv3' than in 'Pacific Early'. According to the metabolome and transcriptome analysis, in 'Jilv3', the energy supply of the TCA cycle was improved, and flavonoid biosynthesis increased. As a result, its adaptability to drought stress improved.

CONCLUSIONS

These findings help to better reveal the molecular mechanism underlying how asparagus responds to drought stress and improve researchers' ability to screen drought-tolerant asparagus varieties as well as breed new varieties.

Metabolite profiling and transcriptomic analyses demonstrate the effects of biocontrol agents on alkaloid accumulation in Fritillaria thunbergii

BACKGROUND

During Fritillaria thunbergii planting, pests and diseases usually invade the plant, resulting in reduced yield and quality. Previous studies have demonstrated that using biocontrol agents can effectively control grubs and affect the steroid alkaloids content in F. thunbergii. However, the molecular regulatory mechanisms underlying the differences in the accumulation of steroid alkaloids in response to biocontrol agents remain unclear.

RESULTS

Combined transcriptomic and metabolic analyses were performed by treating the bulbs of F. thunbergii treated with biocontrol agents during planting. Otherwise, 48 alkaloids including 32 steroid alkaloids, 6 indole alkaloids, 2 scopolamine-type alkaloids, 1 isoquinoline alkaloid, 1 furoquinoline alkaloid, and 6 other alkaloids were identified. The content of steroidal alkaloids particularly peimine, peiminine, and veratramine, increased significantly in the group treated with the biocontrol agents. Transcriptome sequencing identified 929 differential genes using biocontrol agents, including 589 upregulated and 340 downregulated genes. Putative biosynthesis networks of steroid alkaloids have been established and combined with differentially expressed structural unigenes, such as acetyl-CoA C-acetyl-transferase, acelyl-CoAC-acetyltransferase3-hydroxy-3-methylglutaryl-coenzyme A synthase, 1-deoxy-D-xylulose-5-phosphate reductor-isomerase, 2-C-methyl-D-erythritol-4-phosphate cytidylyltransferase and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase. In addition, biological processes such as amino acid accumulation and oxidative phosphorylation were predicted to be related to the synthesis of steroid alkaloids. Cytochrome P450 enzymes also play crucial roles in the steroid alkaloid synthesis. The transcription factor families MYB and bHLH were significantly upregulated after using biocontrol agents.

CONCLUSIONS

Biocontrol agents increased the steroid alkaloids accumulation of steroid alkaloids by affecting key enzymes in the steroid alkaloid synthesis pathway, biological processes of oxidative phosphorylation and amino acid synthesis, cytochrome P450 enzymes, and transcription factors. This study revealed the mechanism underlying the difference in steroidal alkaloids in F. thunbergii after using biocontrol agents, laying the groundwork for future industrial production of steroid alkaloids and ecological planting of medicinal materials in the future.

Sesame (Sesamum indicum L.) response to drought stress: susceptible and tolerant genotypes exhibit different physiological, biochemical, and molecular response patterns

Drought is one of the main environmental stresses affecting the quality and quantity of sesame production worldwide. The present study was conducted to investigate the effect of drought stress and subsequent re-watering on physiological, biochemical, and molecular responses of two contrasted sesame genotypes (susceptible vs. tolerant). Results showed that plant growth, photosynthetic rate, stomatal conductance, transpiration rate, and relative water content were negatively affected in both genotypes during water deficit. Both genotypes accumulated more soluble sugars, free amino acids, and proline and exhibited an increased enzyme activity for peroxidase, catalase, superoxide dismutase, and pyruvate dehydrogenase in response to drought damages including increased lipid peroxidation and membrane disruption. However, the tolerant genotype revealed a more extended root system and a more efficient photosynthetic apparatus. It also accumulated more soluble sugars (152%), free amino acids (48%), proline (75%), and antioxidant enzymes while showing lower electrolyte leakage (26%), lipid peroxidation (31%), and starch (35%) content, compared to the susceptible genotype at severe drought. Moreover, drought-related genes such as MnSOD1, MnSOD2, and PDHA-M were more expressed in the tolerant genotype, which encode manganese-dependent superoxide dismutase and the alpha subunit of pyruvate dehydrogenase, respectively. Upon re-watering, tolerant genotype recovered to almost normal levels of photosynthesis, carboxylation efficiency, lipid peroxidation, and electrolyte leakage, while susceptible genotype still suffered critical issues. Overall, these results suggest that a developed root system and an efficient photosynthetic apparatus along with the timely and effective accumulation of protective compounds enabled the tolerant sesame to withstand stress and successfully return to a normal growth state after drought relief. The findings of this study can be used as promising criteria for evaluating genotypes under drought stress in future sesame breeding programs.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01372-y.