Ethylene enhanced waterlogging tolerance by changing root architecture and inducing aerenchyma formation in maize seedlings

The role of ethylene in the regulation of plant response mechanisms to waterlogging stress

Waterlogging stands as a common environmental challenge, significantly affecting plant growth, yield, and, in severe cases, survival. In response to waterlogging stress, plants exhibit a series of intricate physiologic, metabolic, and morphologic adaptations. Notably, the gaseous phytohormone ethylene is rapidly accumulated in the plant submerged tissues, assuming an important regulatory factor in plant-waterlogging tolerance. In this review, we summarize recent advances in research on the mechanisms of ethylene in the regulation of plant responses to waterlogging stress. Recent advances found that both ethylene biosynthesis and signal transduction make indispensable contributions to modulating plant adaptation mechanisms to waterlogged condition. Ethylene was also discovered to play an important role in plant physiologic metabolic responses to waterlogging stress, including the energy mechanism, morphologic adaptation, ROS regulation and interactions with other phytohormones. The comprehensive exploration of ethylene and its associated genes provides valuable insights into the precise strategies to leverage ethylene metabolism for enhancing plant resistance to waterlogging stress.

Raffinose catabolism enhances maize waterlogging tolerance by stimulating adventitious root growth and development

Raffinose mitigates plant heat, drought, and cold stresses; however, whether raffinose contributes to plant waterlogging tolerance is unknown. The maize raffinose synthase mutant zmrafs-1 had seedlings that lack raffinose, generated fewer and shorter adventitious roots, and were more sensitive to waterlogging stress, while overexpression of the raffinose synthase gene, ZmRAFS, increased raffinose content, stimulated adventitious root formation, and enhanced waterlogging tolerance of maize seedlings. Transcriptome analysis of null segregant seedlings compared with zmrafs-1, particularly when waterlogged, revealed that the expression of genes related to galactose metabolism and the auxin biosynthetic pathway were up-regulated by raffinose. Additionally, indole-3-acetic acid content was significantly decreased in zmrafs-1 seedlings and increased in ZmRAFS-overexpressing seedlings. Inhibition of the hydrolysis of raffinose by 1-deoxygalactonojirimycin decreased the waterlogging tolerance of maize seedlings, the expression of genes encoding proteins related to auxin transport-related genes, and the indole-3-acetic acid level in the seedlings, indicating that the hydrolysis of raffinose is necessary for maize waterlogging tolerance. These data demonstrate that raffinose catabolism stimulates adventitious root formation via the auxin signaling pathway to enhance maize waterlogging tolerance.

Flavonoid metabolism plays an important role in response to lead stress in maize at seedling stage

BACKGROUND

Pb stress, a toxic abiotic stress, critically affects maize production and food security. Although some progress has been made in understanding the damage caused by Pb stress and plant response strategies, the regulatory mechanisms and resistance genes involved in the response to lead stress in crops are largely unknown.

RESULTS

In this study, to uncover the response mechanism of maize to Pb stress phenotype, physiological and biochemical indexes, the transcriptome, and the metabolome under different concentrations of Pb stress were combined for comprehensive analysis. As a result, the development of seedlings and antioxidant system were significantly inhibited under Pb stress, especially under relatively high Pb concentrations. Transcriptome analysis revealed 3559 co-differentially expressed genes(co-DEG) under the four Pb concentration treatments (500 mg/L, 1000 mg/L, 2000 mg/L, and 3000 mg/L Pb(NO3)2), which were enriched mainly in the GO terms related to DNA-binding transcription factor activity, response to stress, response to reactive oxygen species, cell death, the plasma membrane and root epidermal cell differentiation. Metabolome analysis revealed 72 and 107 differentially expressed metabolites (DEMs) under T500 and T2000, respectively, and 36 co-DEMs. KEGG analysis of the DEMs and DEGs revealed a common metabolic pathway, namely, flavonoid biosynthesis. An association study between the flavonoid biosynthesis-related DEMs and DEGs revealed 20 genes associated with flavonoid-related metabolites, including 3 for genistin and 17 for calycosin.

CONCLUSION

In summary, the study reveals that flavonoid metabolism plays an important role in response to Pb stress in maize, which not only provides genetic resources for the genetic improvement of maize Pb tolerance in the future but also enriches the theoretical basis of the maize Pb stress response.

Regulation of photosynthetic function and reactive oxygen species metabolism in sugar beet (Beta vulgaris L.) cultivars under waterlogging stress and associated tolerance mechanisms

Sugar beet (Beta vulgaris L.) is an economically important sugar crop worldwide that is susceptible to sudden waterlogging stress during seedling cultivation, which poses a major threat to sugar beet development and production. Our understanding of the physiological basis of waterlogging tolerance in sugar beet is limited. To investigate the photosynthetic adaptation strategies of sugar beet to waterlogging stress conditions, the tolerant cultivar KUHN1260 (KU) and sensitive cultivar SV1433 (SV) were grown under waterlogging stress, and their photosynthetic function and reactive oxygen species (ROS) metabolism were assessed. Our results showed that waterlogging stress significantly reduced the photosynthetic pigment content, rubisco activity, and expression level of the photosynthetic enzyme genes SvRuBP, SvGAPDH, and SvPRK, gas exchange parameters, and chlorophyll fluorescence parameters, induced damage to the ultrastructure of the chloroplast of the two sugar beet cultivars, inhibited the photosynthetic carbon assimilation capacity of sugar beet leaves, damaged the structural stability of photosystem II (PSII), and disturbed the equilibrium between electrons at the acceptor and donor sides of PSII, which was the result of stomatal and non-stomatal limiting factors. Moreover, the level of ROS, H2O2, and O2▪-, antioxidant enzyme activity, and gene expression levels in the leaves of the two sugar beet cultivars increased over time under waterlogging stress; ROS accumulation was lower and antioxidant enzyme activities and gene expression levels were higher in the waterlogging-tolerant cultivar (KU) than the waterlogging-sensitive cultivar (SV). In sum, these responses in the more tolerant cultivars are associated with their resistance to waterlogging stress. Our findings will aid the breeding of waterlogging-tolerant sugar beet cultivars.

Millmeter-wave irradiation regulates mRNA-expression and the ubiquitin-proteasome system in wheat exposed to flooding stress

The irradiation with millimeter-wave (MMW) of wheat seeds promotes root growth under flooding stress; however, its role is not completely clarified. Nuclear proteomics was performed, to reveal the role of MMW irradiation in enhancing flooding tolerance. The purity of nuclear fractions purified from roots was verified. Histone, which is a protein marker for nuclear-purification efficiency, was enriched; and cytosolic ascorbate peroxidase was reduced in the nuclear fraction. The principal-component analysis of proteome displayed that the irradiation of seeds affected nuclear proteins in roots grown under flooding stress. Proteins detected using proteomic analysis were verified using immunoblot analysis. Histone H3 accumulated under flooding stress; however, it decreased to the control level by irradiation. Whereas the ubiquitin accumulated in roots grown under stress when seeds were irradiated. These results suggest that MMW irradiation improves wheat-root growth under flooding stress through the regulation of mRNA-expression level and the ubiquitin-proteasome system. SIGNIFICANCE: To reveal the role of millimeter-wave irradiation in enhancing flooding tolerance in wheat, nuclear proteomics was performed. The principal-component analysis of proteome displayed that irradiation of seeds affected nuclear proteins in roots grown under flooding stress. Proteins detected using proteomic analysis were verified using immunoblot analysis. Histone H3 accumulated under flooding stress; however, it decreased to the control level with irradiation. Whereas the ubiquitin accumulated in roots grown under stress when seeds were irradiated. These results suggest that millimeter-wave irradiation improves wheat-root growth under flooding stress through the regulation of mRNA-expression level and the ubiquitin-proteasome system.