LpNAC6 reversely regulates the alkali tolerance and drought tolerance of Lilium pumilum

LpNAC5 positively regulates drought, salt and alkalinity tolerance of Lilium pumilum

NACs (NAM、ATAF1/2、CUC1/2), as a large family of plant transcription factors, are widely involved in abiotic stress responses. This study aimed to isolate and clone a novel stress-responsive transcription factor LpNAC5 from Lilium pumilum bulbs. Drought, salt, alkali, and ABA stresses induced the expression of LpNAC5. Transgenic tobacco plants overexpressing LpNAC5 were generated using the Agrobacterium-mediated method to understand the role of this factor in stress response. These plants exhibited increased tolerance to drought, salt, and alkali stresses. The tobacco plants overexpressing LpNAC5 showed strong drought, salt, and alkaline tolerance. Under the three abiotic stresses, the activities of antioxidant enzymes were enhanced, the contents of proline and chlorophyll increased, and the contents of malondialdehyde decreased. The functional analysis revealed that LpNAC5 enabled plants to positively regulate drought and salt stresses. These findings not only provided valuable insights into stress tolerance mechanisms in L. pumilum but also offered a potential genetic resource for breedi.

Regulation of Root Exudation in Wheat Plants in Response to Alkali Stress

Soil alkalization is an important environmental factor limiting crop production. Despite the importance of root secretion in the response of plants to alkali stress, the regulatory mechanism is unclear. In this study, we applied a widely targeted metabolomics approach using a local MS/MS data library constructed with authentic standards to identify and quantify root exudates of wheat under salt and alkali stresses. The regulatory mechanism of root secretion in alkali-stressed wheat plants was analyzed by determining transcriptional and metabolic responses. Our primary focus was alkali stress-induced secreted metabolites (AISMs) that showed a higher secretion rate in alkali-stressed plants than in control and salt-stressed plants. This secretion was mainly induced by high-pH stress. We discovered 55 AISMs containing -COOH groups, including 23 fatty acids, 4 amino acids, 1 amino acid derivative, 7 dipeptides, 5 organic acids, 9 phenolic acids, and 6 others. In the roots, we also discovered 29 metabolites with higher levels under alkali stress than under control and salt stress conditions, including 2 fatty acids, 3 amino acid derivatives, 1 dipeptide, 2 organic acids, and 11 phenolic acids. These alkali stress-induced accumulated carboxylic acids may support continuous root secretion during the response of wheat plants to alkali stress. In the roots, RNAseq analysis indicated that 5 6-phosphofructokinase (glycolysis rate-limiting enzyme) genes, 16 key fatty acid synthesis genes, and 122 phenolic acid synthesis genes have higher expression levels under alkali stress than under control and salt stress conditions. We propose that the secretion of multiple types of metabolites with a -COOH group is an important pH regulation strategy for alkali-stressed wheat plants. Enhanced glycolysis, fatty acid synthesis, and phenolic acid synthesis will provide more energy and substrates for root secretion during the response of wheat to alkali stress.

PvARL1 Increases Biomass Yield and Enhances Alkaline Tolerance in Switchgrass (Panicum virgatum L.)

Switchgrass is an important bioenergy crop valued for its biomass yield and abiotic tolerance. Alkali stress is a major abiotic stress that significantly impedes plant growth and yield due to high salinity and pH; however, the response mechanism of switchgrass to alkali stress remains limited. Here, we characterized PvARL1, an ARF-like gene, which was up-regulated in both the shoot and root tissues under alkali stress conditions. Overexpression of PvARL1 not only improved alkali tolerance but also promoted biomass yield with more tiller and higher plant height in switchgrass. Moreover, PvARL1 overexpression lines displayed higher capacities in the maintenance of water content and photosynthetic stability compared with the controls under alkali treatments. A significant reduction in the ratio of electrolyte leakage, MDA content, and reactive oxygen species (ROS) showed that PvARL1 plays a positive role in protecting cell membrane integrity. In addition, PvARL1 also negatively affected the K+ efflux or uptake in roots to alleviate ion toxicity under alkali treatments. Overall, our results suggest that PvARL1 functions as a positive regulator in plant growth as well as in the plant response to alkali stress, which could be used to improve switchgrass biomass yield and alkali tolerance genetically.

Integrated transcriptome and metabolome revealed the drought responsive metabolic pathways in Oriental Lily (Lilium L.)

Objective

Lily is an essential ornamental flowering species worldwide. Drought stress is a major constraint affecting the morphology and physiology and lily leaves and flowers. Therefore, understanding the molecular mechanism underlying lily response to drought stress is important.

Method

Transcriptome and metabolome analysis were performed on Oriental Lily subjected to drought stress.

Result

Most transcription factors and metabolites yielded by the conjoint analysis displayed a downregulated expression pattern. Differential genes and metabolites mainly co-enriched in glycolic pathways related to sugars, such as galactose, and sucrose, glycolysis and gluconeogenesis, indicating that drought stress reduced the sugar metabolism level of Oriental Lily. Combined with transcriptome and metabolome data, nine pairs of differentially expressed metabolites and the genes (p < 0.05) were obtained. Interestingly, a gene named TRINITY_DN2608 (encoding a type of alpha-D-glucose) cloned and its overexpression lines in Arabidopsis thaliana was generated. Overexpression of TRINITY_DN2608 gene elevated the susceptibility to drought stress possibly by suppressing the glucose level.

Conclusion

The enrichment of sugar-related pathways advocates the potential role of glucose metabolism in drought stress. Our study provides theoretical information related to the glucose-mediated drought response and would be fruitful in future lily breeding programs.

Time-Course Transcriptome Analysis of Aquilegia vulgaris Root Reveals the Cell Wall's Roles in Salinity Tolerance

Salt stress has a considerable impact on the development and growth of plants. The soil is currently affected by salinisation, a problem that is becoming worse every year. This means that a significant amount of salt-tolerant plant material needs to be added. Aquilegia vulgaris has aesthetically pleasing leaves, unique flowers, and a remarkable tolerance to salt. In this study, RNA-seq technology was used to sequence and analyse the transcriptome of the root of Aquilegia vulgaris seedlings subjected to 200 mM NaCl treatment for 12, 24, and 48 h. In total, 12 Aquilegia vulgaris seedling root transcriptome libraries were constructed. At the three time points of salt treatment compared with the control, 3888, 1907, and 1479 differentially expressed genes (DEGs) were identified, respectively. Various families of transcription factors (TFs), mainly AP2, MYB, and bHLH, were identified and might be linked to salt tolerance. Gene Ontology (GO) analysis of DEGs revealed that the structure and composition of the cell wall and cytoskeleton may be crucial in the response to salt stress. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the DEGs showed a significant enrichment of the pentose and glucuronate interconversion pathway, which is associated with cell wall metabolism after 24 and 48 h of salt treatment. Based on GO and KEGG analyses of DEGs, the pentose and glucuronate interconversion pathway was selected for further investigation. AP2, MYB, and bHLH were found to be correlated with the functional genes in this pathway based on a correlation network. This study provides the groundwork for understanding the key pathways and gene networks in response to salt stress, thereby providing a theoretical basis for improving salt tolerance in Aquilegia vulgaris.

Transcriptome profiling revealed salt stress-responsive genes in Lilium pumilum bulbs

Lilium pumilum is an important ornamental, culinary and medicinal bulbous plants with salt tolerance. However, salt tolerance of lily, particularly the bulb, has been studied relatively little, which brings challenges to the cultivation of lily varieties with high salt tolerance. Here, we performed transcriptome sequencing on the bulb organs of L. pumilum under salt stress treatment, analyzed differential gene expressed levels and then identified several key genes associated with salt stress tolerance at genome-wide scale. For the first time, we revealed the obvious response against salt stress for L. pumilum bulb organs, while distinct from those for root organs. Several key genes obtained through transcriptome analysis and DEG screening include NF-YB3 transcription factor, metallothionein type 2 protein, vicilin like seed storage protein and bidirectional sugar transporter SWEET14. Rather than typical ROS scavengers like superoxide dismutase, peroxidase, and glutathione transferase, non-typical ROS scavengers such as the metallothionein type 2 protein, and vicilin like seed storage protein were upregulated in our work. The bidirectional sugar transporter SWEET14 protein and the hormone signaling proteins such as E3-ubiquitin protein ligases, PYL4 and protein phosphatase 2C were also upregulated, suggesting the role of sugars and hormones in the bulb organ responses to salt stress. Co-expression analysis of the DEGs further confirmed that NF-YB3 transcription factor acted as a hub gene, suggesting that salt stress can promote flowering of L. pumilum. Taken together, we identified important candidate genes associated with salt tolerance of the L. pumilum bulb organs, which may provide the excellent basis for further in-depth salt tolerance mechanisms of the lily bulbs.