Heterologous expression of MiHAK14 enhances plant tolerance to K+ deficiency and salinity stresses in Arabidopsis

As one of the most abundant ions in cells, potassium (K+) is closely related to plant growth and development and contributes to plant tolerance to various abiotic stresses. However molecular mechanisms towards K+ uptake and transport are unclear in tropic fruit trees. In this study, 18 KT/HAK/KUP family genes (MiHAKs) were isolated and characterized in mango. Results showed that MiHAKs were unevenly expressed in distinct tissues and were differentially responded to K+ depletion, PEG, and NaCl stresses in roots, in which K+ depletion and PEG treatment significantly enhanced while NaCl treatment mainly reduced responsive MiHAK genes. In particular, MiHAK14 was the most abundant KT/HAK/KUP family gene in mango, especially in roots. Functional complementation in TK2420 mutant revealed that MiHAK14 could uptake external K+. Moreover, overexpression of MiHAK14 in Arabidopsis enhanced plant tolerance to K+ depletion and NaCl stresses with strengthened K+ nutritional status and ROS scavenging ability. This study provides molecular basis for further functional studies of KT/HAK/KUP transporters in tropic fruit trees, and favorably demonstrates the essentiality of K+ homeostasis in plant tolerance to abiotic stresses, including K+ deficiency and NaCl stress.

Multi-Omics Analysis of Lipid Metabolism for a Marine Probiotic Meyerozyma guilliermondii GXDK6 Under High NaCl Stress

Investigating microbial lipid regulation contributes to understanding the lipid-dependent signal transduction process of cells and helps to improve the sensitivity of microorganisms to environmental factors by interfering with lipid metabolism, thus beneficial for constructing advanced cell factories of novel molecular drugs. Integrated omics technology was used to systematically reveal the lipid metabolism mechanism of a marine Meyerozyma guilliermondii GXDK6 under high NaCl stress and test the sensitivity of GXDK6 to antibiotics when its lipid metabolism transformed. The omics data showed that when GXDK6 perceived 10% NaCl stress, the expression of AYR1 and NADPH-dependent 1-acyldihydroxyacetone phosphate reductase was inhibited, which weaken the budding and proliferation of cell membranes. This finding was further validated by decreased 64.39% of OD600 under 10% NaCl stress when compared with salt-free stress. In addition, salt stress promoted a large intracellular accumulation of glycerol, which was also verified by exogenous addition of glycerol. Moreover, NaCl stress remarkably inhibited the expression of drug target proteins (such as lanosterol 14-alpha demethylase), thereby increasing sensitivity to fluconazole. This study provided new insights into the molecular mechanism involved in the regulation of lipid metabolism in Meyerozyma guilliermondii strain and contributed to developing new methods to improve the effectiveness of killing fungi with lower antibiotics.

Evaluation of Thellungiella halophila ST7 for improving salt tolerance in cotton

Background Gossypium hirsutum (upland cotton) is one of the principal fiber crops in the world. Cotton yield is highly affected by abiotic stresses, among which salt stress is considered as a major problem around the globe. Transgenic approach is efficient to improve cotton salt tolerance but depending on the availability of salt tolerance genes. Results In this study we evaluated salt tolerance candidate gene ST7 from Thellungiella halophila, encoding a homolog of Arabidopsis aluminum-induced protein, in cotton. Our results showed that ThST7 overexpression in cotton improved germination under NaCl stress as well as seedling growth. Our field trials also showed that ThST7 transgenic cotton lines produced higher yield under salt stress conditions. The improved salt tolerance of the transgenic cotton lines was partially contributed by enhanced antioxidation as shown by diaminobenzidine (DAB) and nitrotetrazolium blue chloride (NBT) staining. Moreover, transcriptomic analysis of ThST7 overexpression lines showed a significant upregulation of the genes involved in ion homeostasis and antioxidation, consistent with the salt tolerance phenotype of the transgenic cotton. Conclusions Our results demonstrate that ThST7 has the ability to improve salt tolerance in cotton. The ThST7 transgenic cotton may be used in cotton breeding for salt tolerance cultivars.

Effects of Salt Stress on Absorption And Distribution of Osmotic Ions in Wheat Seedlings

Effects of salt stress on absorption and distribution of osmotic ions in wheat seedlings were studied with 4 winter wheat varieties under NaCl stress by exploring dynamic changes of Ca2+, K+, Na+, Ca2+/Na+, K+/Na+ and Na+ limiting ability. The results showed that the contents of K+, Ca2+ and the K+/Na+ ratio gradually decreased in a manner of both salt concentration dependent and stress time dependent. The extent of reduction of K+ and Ca2+ in root was much more severe than that in shoot. The ability of Na+ limiting in QM6 and DK961 was stronger than that in JM22 and QF1. These results indicate that the maintenance of higher Na+ content in root, Na+ limiting ability, Ca2+ and K+ concentration will be the main physiological traits for the salt-tolerance of wheat. Bangladesh J. Bot. 50(4): 1209-1214, 2021 (December)

Transcriptome Analysis of Arbuscular Mycorrhizal Casuarina glauca in Damage Mitigation of Roots on NaCl Stress

Casuarina glauca grows in coastal areas suffering long-term damage due to high salt stress. Arbuscular mycorrhizal fungi (AMF) can colonize their roots to alleviate the effects of salt stress. However, the specific molecular mechanism still needs to be further explored. Our physiological and biochemical analysis showed that Rhizophagus irregularis inoculation played an important role in promoting plant growth, regulating ion balance, and changing the activity of antioxidant enzymes. Transcriptome analysis of roots revealed that 1827 differentially expressed genes (DEGs) were affected by both R. irregularis inoculation and NaCl stress. The enrichment of GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) showed that most of these DEGs were significantly enriched in ion transport, antioxidant enzyme activity, carbohydrate metabolism, and cell wall. HAK5, KAT3, SKOR, PIP1-2, PER64, CPER, GLP10, MYB46, NAC43, WRKY1, and WRKY19 were speculated to play the important roles in the salt tolerance of C. glauca induced by R. irregularis. Our research systematically revealed the effect of R. irregularis on the gene expression of C. glauca roots under salt stress, laying a theoretical foundation for the future use of AMF to enhance plant tolerance to salt stress.

Response of enzymatic and non-enzymatic antioxidant systems in Excoecaria agallocha to salt stress

The effect of NaCl stress on antioxidant enzymes activities was investigated in the leaves of Excoecaria agallocha. Plants were subjected to different levels of NaCl. 100 to 1000 mM. Above 500 mM these mangrove seedlings did not survive. The leaves of 60 day old plants were used for the analysis of enzyme activities. Parameters of enzymatic and non enzymatic antioxidants such as catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), polyphenol oxidase (PPO), superoxide dismutase (SOD), ascorbic acid (ASA) and alpha tocopherol were determined. The highest CAT, POD, APX, PPO and SOD activities in the leaf and root enhanced gradually up to 300 mM of NaCl, the highest ASA and tocopherol activities in the leaf and root were observed at 500 mM of NaCl. These data suggest that the capacity to limit oxidative damage is important for the salt tolerance of E. agallocha.

Heterologous Expression of ZmNF-YA12 Confers Tolerance to Drought and Salt Stress in Arabidopsis

Drought and salinity are serious environmental factors limiting the growth and productivity of plants worldwide. Therefore, it is necessary to develop ways to improve drought and salinity stress tolerance in plants. In this study, a drought-responsive nuclear factor Y subunit A gene, ZmNF-YA12, was cloned from maize. qPCR revealed ZmNF-YA12 transcript in all vegetative and reproductive tissues, with higher levels in young roots. Expression analyses of maize revealed that ZmNF-YA12 was induced by abscisic acid (ABA), jasmonic acid (JA), and abiotic stresses, including dehydration, high salinity, cold, and polyethylene glycol (PEG) treatment. The heterologous expression of ZmNF-YA12 in Arabidopsis plants resulted in increased root length and better plant growth than in wild-type (WT) plants under conditions of mannitol, salt, and JA stress on 1/2 MS medium. Transgenic Arabidopsis showed improved tolerance to drought and salt stresses in soil, and higher proline content and lower malondialdehyde (MDA) content than WT controls. The transgenic plants also maintained higher peroxidase (POD) activities than WT plants under conditions of NaCl stress. A yeast two-hybrid experiment demonstrated that ZmNF-YA12 interacted with ZmNF-YC1 and ZmNF-YC15. Moreover, the transcript levels of stress-responsive genes (RD29A, RD29B, RAB18, and RD22) were markedly increased in transgenic lines under conditions of drought and salt stress. These observations suggested that the ZmNF-YA12 gene confers drought and salt stress tolerance, and has potential applications in molecular breeding with maintenance of production under conditions of stress.

Elucidating the Molecular Mechanisms by which Seed-Borne Endophytic Fungi, Epichloë gansuensis, Increases the Tolerance of Achnatherum inebrians to NaCl Stress

Seed-borne endophyte Epichloë gansuensis enhance NaCl tolerance in Achnatherum inebrians and increase its biomass. However, the molecular mechanism by which E. gansuensis increases the tolerance of host grasses to NaCl stress is unclear. Hence, we firstly explored the full-length transcriptome information of A. inebrians by PacBio RS II. In this work, we obtained 738,588 full-length non-chimeric reads, 36,105 transcript sequences and 27,202 complete CDSs from A. inebrians. We identified 3558 transcription factors (TFs), 15,945 simple sequence repeats and 963 long non-coding RNAs of A. inebrians. The present results show that 2464 and 1817 genes were differentially expressed by E. gansuensis in the leaves of E+ and E− plants at 0 mM and 200 mM NaCl concentrations, respectively. In addition, NaCl stress significantly regulated 4919 DEGs and 502 DEGs in the leaves of E+ and E− plants, respectively. Transcripts associated with photosynthesis, plant hormone signal transduction, amino acids metabolism, flavonoid biosynthetic process and WRKY TFs were differentially expressed by E. gansuensis; importantly, E. gansuensis up-regulated biology processes (brassinosteroid biosynthesis, oxidation–reduction, cellular calcium ion homeostasis, carotene biosynthesis, positive regulation of proteasomal ubiquitin-dependent protein catabolism and proanthocyanidin biosynthesis) of host grass under NaCl stress, which indicated an increase in the ability of host grasses’ adaptation to NaCl stress. In conclusion, our study demonstrates the molecular mechanism for E. gansuensis to increase the tolerance to salt stress in the host, which provides a theoretical basis for the molecular breed to create salt-tolerant forage with endophytes.