MicroRNAs (miRNAs) are versatile regulators of gene expression at both the transcription and post-transcription levels. The microRNA miR396 plays vital roles in growth, development, and resistance to abiotic stresses in many plant species. However, the roles and functions of miR396 in soybeans are not well understood. Here, we report that Gm-miR396a influences soybean development and salinity tolerance. We found that soybean miR396a was responsive to salt stress. Gm-miR396a gene-edited lines (miR396a-GEs), created using CRISPR/Cas9, exhibited more branches, higher grain yields, and greater salinity tolerance than control plants. The transcripts in lines with altered abundance of miR396a-GE were significantly enriched for biological processes related to hormone regulation. Overexpression of the Gm-miR396a precursor (pre-miR396a-OE) resulted in developmental deficiencies including dwarfness, abnormal inflorescences and flowers, smaller and fewer seeds, and small leaves with larger and more numerous stomata. Transcriptome analysis indicated photosynthesis-related genes were downregulated in pre-miR396a-OE plants. These results contribute valuable insights into the function of Gm-miR396a in soybeans and hold promise for enhancing soybean yield and salinity tolerance through germplasm innovation.

DREBs are transcription factors that regulate abiotic stress tolerance in plants. Previously, we reported that wheat transgenic lines overexpressing GmDREB1 showed increased tolerance to drought and salt stress. However, the molecular basis of increased tolerance is still poorly understood, and whether the overexpression of DREB will cause unexpected effects is also of concern. We performed seed metabolic profiling of the genetically modified (GM) wheat T349 and three non-GM cultivars with LC-MS to identify the metabolic basis of stress tolerance and to assess the unexpected effects of exogenous gene insertion. Although we did not note the appearance of novel metabolites or the disappearance of existing metabolites, overexpression of the transcription factor GmDREB1 in T349 wheat influenced metabolite levels in seeds. Increased levels of stress tolerance-associated metabolites were found in the stress-sensitive non-transgenic acceptor counterpart J19, while metabolites associated with cell membrane structure and stability accumulated in T349. Among these metabolites in T349, most showed levels similar to those in the non-GM wheats. Overexpression of GmDREB1 in T349 may cause a shift in its metabolic profile leading to down-regulation of several energy-consuming processes to favor increased yield under stress conditions, which is a reasonable expectation of breeders while creating the GM wheat and GmDREB1 overexpression did not cause unexpected effects in T349 seeds. These results may be helpful for GM crop research and risk assessment.

Small auxin-upregulated RNAs (SAURs) are genes regulated by auxin and environmental factors. In this study, we identified a SAUR gene in wheat, TaSAUR75. Under salt stress, TaSAUR75 is downregulated in wheat roots. Subcellular localization revealed that TaSAUR75 was localized in both the cytoplasm and nucleus. Overexpression of TaSAUR75 increased drought and salt tolerance in Arabidopsis. Transgenic lines showed higher root length and survival rate and higher expression of some stress-responsive genes than control plants under salt and drought stress. Less H₂O₂ accumulated in transgenic lines than in control plants under drought stress. Our findings reveal a positive regulatory role of the auxin-responsive gene TaSAUR75 in plant responses to drought and salt stress and provide a candidate gene for improvement of abiotic stress tolerance in crop breeding.