Saline−alkaline stress is a critical abiotic stress that negatively affects plants’ growth and development. Considerably higher enhancements in plant tolerance to saline−alkaline stress have often been observed in polyploid plants compared to their diploid relatives, the underlying mechanism of which remains elusive. In this study, we explored the variations in morphological and physiological characteristics, phytohormones, and genome-wide gene expression between an autotetraploid rice and its diploid relative in response to alkaline stress. It was observed that the polyploidization in the autotetraploid rice imparted a higher level of alkaline tolerance than in its diploid relative. An eclectic array of physiological parameters commonly used for abiotic stress, such as proline, soluble sugars, and malondialdehyde, together with the activities of some selected antioxidant enzymes, was analyzed at five time points in the first 24 h following the alkaline stress treatment between the diploid and autotetraploid rice. Phytohormones, such as abscisic acid and indole-3-acetic acid were also comparatively evaluated between the two types of rice with different ploidy levels under alkaline stress. Transcriptomic analysis revealed that gene expression patterns were altered in accordance with the variations in the cellular levels of phytohormones between diploid and autotetraploid plants upon alkaline stress. In particular, the expression of genes related to peroxide and transcription factors was substantially upregulated in autotetraploid plants compared to diploid plants in response to the alkaline stress treatment. In essence, diploid and autotetraploid rice plants exhibited differential gene expression patterns in response to the alkaline stress, which may shed more light on the mechanism underpinning the ameliorated plant tolerance to alkaline stress following genome duplication.

Osmotic stress caused by drought and high salinity is the key factor limiting plant growth. However, its underlying molecular regulatory mechanism remains unclear. In this study, we found the stress-related gene Zm00001d019704 (ZmSRG7) based on transcriptome sequencing results previously obtained in the laboratory and determined its biological function in maize. We found that ZmSRG7 was significantly expressed in both roots and leaves under 10% PEG6000 or 150 mM NaCl. Subcellular localization showed that the gene was localized in the nucleus. The germination rate and root length of the ZmSRG7 overexpressing lines were significantly increased under drought or salt stress compared with the control. However, after drought stress, the survival rate and relative water content of maize were increased, while the water loss rate was slowed down. Under salt stress, the Na⁺ concentration and Na⁺: K⁺ ratio of maize was increased. In addition, the contents of antioxidant enzymes and proline in maize under drought or salt stress were higher than those in the control, while the contents of MDA, H₂O₂ and O₂⁻ were lower than those in the control. The results showed that the ZmSRG7 gene played its biological function by regulating the ROS signaling pathway. An interaction between ZmSRG7 and the Zmdhn1 protein was found using a yeast two-hybrid experiment. These results suggest that the ZmSRG7 gene can improve maize tolerance to drought or salt by regulating hydrogen peroxide homeostasis.

Drought stress is one of the major adversity stresses affecting soybean (Glycine max [L.] Merr.) yield. Late embryogenesis abundant protein (LEA protein) is a large family of proteins widely distributed in various types of organisms, and this class of proteins plays an important role in protecting proteins, membrane lipids, and lipids inside the cell. The soybean GmPM35 gene is a member of the LEA_6 subfamily. The expression of the GmPM35 gene was significantly increased after drought stress in soybeans. A subcellular localization assay confirmed that the gene acts on the cell membrane. Against wild-type Arabidopsis thaliana, we found that Arabidopsis lines overexpressing the GmPM35 gene were significantly more drought-tolerant at germination and seedling stages under drought stress. To further investigate the drought tolerance function of this gene in soybeans, nine overexpression lines of the T₃ generation soybean GmPM35 gene and two editing lines of the T₃ generation soybean GmPM35 gene were obtained by Agrobacterium-mediated method using a wild-type soybean strain (JN28) as a receptor. Germination rate, root length, chlorophyll (CHL) content, Proline (Pro) content, malondialdehyde (MDA) content, superoxide anion (O₂^•−) content, hydrogen peroxide (H₂O₂) content, (NBT, DAB) staining, and activities of antioxidant enzymes (CAT, SOD, POD), and photosynthetic physiological indexes of the three different types of strains were measured and analyzed before and after drought stress. Combined with the results of rehydration experiments and physiological and biochemical indices, we found that overexpression of the GmPM35 gene protected the activities of antioxidant enzymes under drought stress. The activities of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were increased by an average of 34.28%, 26.12%, and 30.01%, respectively, in soybean plants overexpressing the GmPM35 gene compared with wild-type soybeans. Under drought stress conditions, soybean plants overexpressing the GmPM35 gene showed an average increase of 76.81% in photosynthesis rate (Pn), 39.8% in transpiration rate (Tr), 126% in stomatal conductance (Gs), 47.71% in intercellular CO₂ concentration (Ci), and 26.44% in instantaneous water use efficiency (WUEi). The improvement of these indexes helped to reduce the accumulation of reactive oxygen species (ROS) in the plants. In addition, we found that under drought stress, the MDA content was reduced by an average of 18.8%, and the Pro content was increased by an average of 60.14% in soybean plants overexpressing the GmPM35 gene, and the changes in these indexes indicated that the plants had stronger antioxidant and osmoregulatory capacities in response to drought stress. In summary, this experiment demonstrated that the GmPM35 gene plays an important role in soybean tolerance to drought stress, and by overexpressing the GmPM35 gene, soybean plants can better tolerate drought stress and maintain normal physiological functions.

Soybean (Glycine max L. Merr.) is rich in proteins, fats, and other nutrients, and the genetic improvement of soybean protein content has long been a key research focus in breeding programs. Based on the chromosome segment substitution line (CSSL) population, this study screened target lines within this population using genotypic and phenotypic information to establish an initial mapping population for soybean seed protein content. Through single-marker analysis, a quantitative trait locus (QTL) interval was mapped to the region between 26,705,080 bp and 33,180,908 bp on chromosome 16, designated as qSPJ_1. A secondary segregating population was constructed based on the initial mapping results for fine mapping, which narrowed the interval to 0.076 Mb. A total of 9 candidate genes were identified within this interval. By comparing amino acid and promoter sequences between the two parents, performing quantitative real-time PCR (qRT-PCR) analysis, and conducting haplotype analysis, Glyma.16G165100 was preliminarily predicted as a candidate gene affecting soybean seed protein content. The single nucleotide polymorphism (SNP) variation sites in its promoter region were significantly associated with the variation in protein content in the resource population. This study provides important theoretical guidance for dissecting the genetic mechanism of soybean seed protein content and advancing its breeding improvement.