No abstract

bZIP transcription factors play key roles in plant growth, development, and stress signaling. A bZIP gene BnbZIP2 (GenBank accession number: KP642148) was cloned from ramie. BnbZIP2 has a 1416 base pair open reading frame, encoding a 471 amino acid protein containing a characteristic bZIP domain and a leucine zipper. BnbZIP2 shares high sequence similarity with bZIP factors from other plants. The BnbZIP2 protein is localized to both nuclei and cytoplasm. Transcripts of BnbZIP2 were found in various tissues in ramie, with significantly higher levels in female and male flowers. Its expression was induced by drought, high salinity, and abscisic acid treatments. Analysis of the cis-elements in promoters of BnbZIP2 identified cis-acting elements involved in growth, developmental processes, and a variety of stress responses. Transgenic Arabidopsis plants' overexpression of BnbZIP2 exhibited more sensitivity to drought and heavy metal Cd stress during seed germination, whereas more tolerance to high-salinity stress than the wild type during both seed germination and plant development. Thus, BnbZIP2 may act as a positive regulator in plants' response to high-salinity stress and be an important candidate gene for molecular breeding of salt-tolerant plants.

Abiotic stresses are one of the significant threats to soybean (Glycine max L.) growth and yields worldwide. Soybean has a crucial role in the global food supply chain and food security and contributes the main protein share compared to other crops. Hence, there is a vast scientific saddle on soybean researchers to develop tolerant genotypes to meet the growing need of food for the huge population. A large portion of cultivated land is damaged by salinity stress, and the situation worsens yearly. In past years, many attempts have increased soybean resilience to salinity stress. Different molecular techniques such as quantitative trait loci mapping (QTL), genetic engineering, transcriptome, transcription factor analysis (TFs), CRISPR/Cas9, as well as other conventional methods are used for the breeding of salt-tolerant cultivars of soybean to safeguard its yield under changing environments. These powerful genetic tools ensure sustainable soybean yields, preserving genetic variability for future use. Only a few reports about a detailed overview of soybean salinity tolerance have been published. Therefore, this review focuses on a detailed overview of several molecular techniques for soybean salinity tolerance and draws a future research direction. Thus, the updated review will provide complete guidelines for researchers working on the genetic mechanism of salinity tolerance in soybean.

Xyloglucan endotransglycosylase/hydrolase (XTH) genes play an important role in plant resistance to abiotic stress. However, systematic studies of the response of Boehmeria nivea (ramie) XTH genes (BnXTHs) to cadmium (Cd) stress are lacking. We sought to identify the BnXTH-family genes in ramie through bioinformatics analyses and to investigate their responses to Cd stress. We identified 19 members of the BnXTH gene family from the ramie genome, referred to as BnXTH1-19, among which BnXTH18 and BnXTH19 were located on no chromosomes and the remaining genes were unevenly distributed across 11 chromosomes. The 19 members were divided into four groups, Groups I/II/IIIA/IIIB, according to their phylogenetic relationships, and these groups were supported by analyses of intron–exon structure and conserved motif composition. A highly conserved catalytic site (HDEIDFEFLG) was observed in all BnXTH proteins. Additionally, three gene pairs (BnXTH6–BnXTH16, BnXTH8–BnXTH9, and BnXTH17–BnXTH18) were obtained with a fragment and tandem-repeat event analysis of the ramie genome. An analysis of cisregulatory elements revealed that BnXTH expression might be regulated by multiple hormones and abiotic and biotic stress responses. In particular, 17 cisregulatory elements related to abiotic and biotic stress responses and 11 cisregulatory elements related to hormone responses were identified. We also found that most BnXTH genes responded to Cd stress, and BnXTH1, BnXTH3, BnXTH6, and BnXTH15 were most likely to contribute to the Cd tolerance of ramie, as evidenced by the substantial increases in expression under Cd treatment. Heterologous expression of BnXTH1, BnXTH6, and BnXTH15 significantly enhanced the Cd tolerance of transgenic yeast cells. These results suggest that the BnXTH gene family is involved in Cd stress responses, laying a theoretical foundation for functional studies of BnXTH genes and the innovative breeding of Cd-tolerant ramie.

Ramie cell walls play an important role in cadmium (Cd) detoxification. However, the Cd binding capacity of the cell wall components and the cell wall compositions among ramie species remains unclear. Therefore, this study compared two ramie populations (‘Dazhuhuangbaima’ (low-Cd-accumulating population) and ‘Zhongzhu 1’ (high-Cd-accumulating population)) with different Cd enrichment characteristics. The two ramie populations were treated with 0, 25, and 75 mg kg−1 Cd for 30 days; then, their root length, plant height, biomass, Cd enrichment in the organs, subcellular Cd distribution, Cd content in the cell wall polysaccharides, and hemicellulose content were determined. The root length, plant height, biomass, and Cd enrichment in all organs were significantly higher (p ≤ 0.05) in ‘Zhongzhu 1’ than in ‘Dazhuhuangbaima’ under Cd stress. In addition, the subcellular Cd distribution analysis revealed that Cd was mainly found in the cell wall in both ramie populations. Among the cell wall fractions, Cd was mainly bound to the hemicelluloses, with 60.38–73.10% and 50.05–64.45% Cd accumulating in the ‘Zhongzhu 1’ and ‘Dazhuhuangbaima’ cell wall hemicelluloses, respectively. However, the Cd concentration in the ‘Zhongzhu 1’ hemicellulose was significantly higher (p ≤ 0.05) than that in the ‘Dazhuhuangbaima’ hemicellulose. Hemicellulose content analysis further revealed that the hemicellulose concentration increased with the Cd concentration in both populations, but it was significantly higher (p ≤ 0.05) in ‘Zhongzhu 1’ than in ‘Dazhuhuangbaima’ across all Cd treatments. Thus, ramie copes under Cd stress by increasing the hemicellulose content in the cell wall. The findings in this study confirm that hemicellulose is the main enrichment site for Cd in ramie. It also provides a theoretical basis for Cd enrichment breeding in ramie.