Accession-specific Parent-of-origin Dependent and Independent Genome Dosage Effects on Salt Tolerance in Arabidopsis Thaliana

Improving the salt stress tolerance of crops is an important goal in plant breeding. Changes in the number of chromosome pairs (i.e. ploidy level) cause genome dosage effects which can result in improved traits or emergence of novel traits. The genetic and epigenetic contribution of maternal or paternal chromosomes can differentially affect physiological and metabolic characteristics of F1 offspring. Hence genome dosage effects can be parent-of-origin independent or dependent. The model plant Arabidopsis thaliana displays both genome dosage and parent-of-origin effects on plant growth under normal, non-stress conditions. Using an insogenic ploidy series of diploid, triploid and tetraploid lines we investigate the extent of genome dosage effects and their parent-of-origin dependency on in vitro salt stress tolerance of seedlings across ten different A. thaliana accessions (genetic backgrounds). We demonstrate genome dosage effects on salt stress tolerance in five accessions, and using reciprocal triploid lines demonstrate parent-of-origin dependent genome dosage effects on salt stress tolerance in three accessions. Our results indicate that epigenetic genome dosage and genome dosage balance effects can have significant impacts on abiotic stress tolerance in plants.

Breeding for salt tolerance in wheat: The contribution of carbon isotopic signatures

Use of low-quality water for supplemental irrigation is expected to become soon a common practice in the Mediterranean area, where durum wheat is the main cultivated cereal. Breeding for salt stress tolerance may contribute to the improvement of wheat resilience to irrigation with brackish water. Various traits can be considered as indicators of salt stress tolerance, which include agronomical and physiological criteria. However, the complexity of salinity tolerance mechanisms, the G × E interaction and the lack of correlation between controlled and open field conditions causes uncertainty in the selection process. The present review highlights the main advantages and limitations of different agronomical and physiological traits used in screening for salt stress tolerance in wheat. Special focus is given to carbon and nitrogen isotope discrimination, that remains a bottleneck in breeding for salt stress tolerance. The use of different statistical tools to analyse data related to salt stress tolerance is also discussed in this review.

Genome-Wide Association Studies of Salt Tolerance at Seed Germination and Seedling Stages in Brassica napus

Most crops are sensitive to salt stress, but their degree of susceptibility varies among species and cultivars. In order to understand the salt stress adaptability of Brassica napus to salt stress, we collected the phenotypic data of 505 B. napus accessions at the germination stage under 150 or 215 mM sodium chloride (NaCl) and at the seedling stage under 215 mM NaCl. Genome-wide association studies (GWAS) of 16 salt tolerance coefficients (STCs) were applied to investigate the genetic basis of salt stress tolerance of B. napus. In this study, we mapped 31 salts stress-related QTLs and identified 177 and 228 candidate genes related to salt stress tolerance were detected at germination and seedling stages, respectively. Overexpression of two candidate genes, BnCKX5 and BnERF3 overexpression, were found to increase the sensitivity to salt and mannitol stresses at the germination stage. This study demonstrated that it is a feasible method to dissect the genetic basis of salt stress tolerance at germination and seedling stages in B. napus by GWAS, which provides valuable loci for improving the salt stress tolerance of B. napus. Moreover, these candidate genes are rich genetic resources for the following exploration of molecular mechanisms in adaptation to salt stress in B. napus.

Physiological Biochemistry-Combined Transcriptomic Analysis Reveals Mechanism of Bacillus cereus G2 Improved Salt-Stress Tolerance of Glycyrrhiza uralensis Fisch. Seedlings by Balancing Carbohydrate Metabolism

Salt stress severely threatens the growth and productivity of Glycyrrhiza uralensis. Previous results found that Bacillus cereus G2 enhanced several carbohydrate contents in G. uralensis under salt stress. Here, we analyzed the changes in parameters related to growth, photosynthesis, carbohydrate transformation, and the glycolysis Embden-Meyerhof-Parnas (EMP) pathway-tricarboxylic acid (TCA) cycle by G2 in G. uralensis under salt stress. Results showed that G2 helped G. uralensis-accumulating photosynthetic pigments during photosynthesis, which could further increase starch, sucrose, and fructose contents during carbohydrate transformation. Specifically, increased soluble starch synthase (SSS) activity caused to higher starch content, which could induce α-amylase (AM) and β-amylase (BM) activities; increased sucrose content due to the increase of sucrose synthase (SS) activity through upregulating the gene-encoding SS, which decreased cell osmotic potential, and consequently, induced invertase and gene-encoding α-glucosidase that decomposed sucrose to fructose, ultimately avoided further water loss; increased fructose content-required highly hexokinase (HK) activity to phosphorylate in G. uralensis, thereby providing sufficient substrate for EMP. However, G2 decreased phosphofructokinase (PFK) and pyruvate kinase (PK) activities during EMP. For inducing the TCA cycle to produce more energy, G2 increased PDH activity that enhanced CA content, which further increased isocitrate dehydrogenase (ICDH) activity and provided intermediate products for the G. uralensis TCA cycle under salt stress. In sum, G2 could improve photosynthetic efficiency and carbohydrate transformation to enhance carbohydrate products, thereby releasing more chemical energy stored in carbohydrates through the EMP pathway-TCA cycle, finally maintain normal life activities, and promote the growth of G. uralensis under salt stress.

Effect of Salt Stress and Foliar Application of Salicylic Acid on Morphological, Biochemical, Anatomical, and Productivity Characteristics of Cowpea (Vigna unguiculata L.) Plants

The present study aimed to investigate the impact of salinity on vegetative growth, chemical constituents, and yields of cowpeas (Vigna unguiculata) and the possible benefits of salicylic acid (SA) on these plants after damage from salinity. To achieve these objectives, two pot experiments were carried out at the Faculty of Agriculture, Al-Azhar University, Egypt, during the two growing seasons of 2019 and 2020. The results revealed that salinity significantly decreased, and SA treatment substantially increased the plant height, number of compound leaves, number of internodes per plant, fresh weights of leaves and stems, productivity, photosynthetic pigments content, and concentrations of nitrogen (N), phosphorus (P), and potassium (K) of the cowpea plants compared with the control. The anatomical structure of stems and leaves of the plants were also investigated, and it was found that positive variations in the anatomical structure of the median portion of the main stems and blades of mature foliage leaves were detected in the stressed and SA-treated plants. In conclusion, SA treatment increased the salt stress tolerance of cowpea plants by improving the morphological and physiological attributes of the plants.

The TSN1 Binding Protein RH31 Is a Component of Stress Granules and Participates in Regulation of Salt-Stress Tolerance in Arabidopsis

Tudor staphylococcal nucleases (TSNs) are evolutionarily conserved RNA binding proteins, which include redundant TSN1 and TSN2 in Arabidopsis. It has been showed TSNs are the components of stress granules (SGs) and regulate plant growth under salt stress. In this study, we find a binding protein of TSN1, RH31, which is a DEAD-box RNA helicase (RH). Subcellular localization studies show that RH31 is mainly located in the nucleus, but under salinity, it translocates to the cytoplasm where it accumulates in cytoplasmic granules. After cycloheximide (CHX) treatment which can block the formation of SGs by interfering with mRNP homeostasis, these cytoplasmic granules disappeared. More importantly, RH31 co-localizes with SGs marker protein RBP47. RH31 deletion results in salt-hypersensitive phenotype, while RH31 overexpression causes more resistant to salt stress. In summary, we demonstrate that RH31, the TSN1 binding protein, is a component of plant SGs and participates in regulation of salt-stress tolerance in Arabidopsis.

Soybean GmMYB133 Inhibits Hypocotyl Elongation and Confers Salt Tolerance in Arabidopsis

REVEILLE (RVE) genes generally act as core circadian oscillators to regulate multiple developmental events and stress responses in plants. It is of importance to document their roles in crops for utilizing them to improve agronomic traits. Soybean is one of the most important crops worldwide. However, the knowledge regarding the functional roles of RVEs is extremely limited in soybean. In this study, the soybean gene GmMYB133 was shown to be homologous to the RVE8 clade genes of Arabidopsis. GmMYB133 displayed a non-rhythmical but salt-inducible expression pattern. Like AtRVE8, overexpression of GmMYB133 in Arabidopsis led to developmental defects such as short hypocotyl and late flowering. Seven light-responsive or auxin-associated genes including AtPIF4 were transcriptionally depressed by GmMYB133, suggesting that GmMYB133 might negatively regulate plant growth. Noticeably, the overexpression of GmMYB133 in Arabidopsis promoted seed germination and plant growth under salt stress, and the contents of chlorophylls and malondialdehyde (MDA) were also enhanced and decreased, respectively. Consistently, the expressions of four positive regulators responsive to salt tolerance were remarkably elevated by GmMYB133 overexpression, indicating that GmMYB133 might confer salt stress tolerance. Further observation showed that GmMYB133 overexpression perturbed the clock rhythm of AtPRR5, and yeast one-hybrid assay indicated that GmMYB133 could bind to the AtPRR5 promoter. Moreover, the retrieved ChIP-Seq data showed that AtPRR5 could directly target five clients including AtPIF4. Thus, a regulatory module GmMYB133-PRR5-PIF4 was proposed to regulate plant growth and salt stress tolerance. These findings laid a foundation to further address the functional roles of GmMYB133 and its regulatory mechanisms in soybean.