Despite the potential of soybean plants to fix nitrogen through symbiotic nodules, salt stress presents significant challenges to their agricultural productivity. A recent study has identified the role of the GmERF13 transcription factor family as key regulators inhibiting the formation of these nodules under salt stress conditions.
Researchers discovered four GmERF13 proteins which are induced by salt stress and function as negative regulators of nodulation. Using the soybean cultivar Williams 82 (W82), they found notable increases in nodule density upon the loss of GmERF13 function, whereas overexpression of the same genes resulted in reduced nodule numbers. The team's findings suggest these transcription factors may play pivotal roles in modulating the soybean plant's response to changing environmental factors, particularly salinity.
Salt levels significantly affected nodule formation, with plants treated at higher concentrations losing their ability to produce these structures. Under optimal conditions, nodules arise from the interaction between soybean roots and nitrogen-fixing bacteria, leading to increased efficiency for nitrogen use. Comprehensive RNA sequencing studies unveiled the stress-induced expression of GmERF13 transposable elements, establishing their contributions to the developmental processes of nodulation.
Seedlings subjected to salt treatment revealed key alterations, emphasizing the necessity of accounting for abiotic stresses during breeding programs. Notably, GmERF13 was shown to interact with GmLBD16a, another transcription factor, undermining its binding capacity to the promoter of GmEXP17c, the latter being integral for nodule development. Through this novel interaction, GmERF13 effectively suppresses the expression of genes necessary for nodule formation under salt conditions.
The research team employed advanced genetic engineering techniques, including CRISPR/Cas9, to create mutants lacking GmERF13, observing subsequent improvements in nodulation, particularly under salt stress. These findings have broadened the current comprehension of molecular mechanisms negatively influencing nodule development, raising hopes for improving resistant soybean cultivars.
Importantly, the expression of GmERF13 genes was shown to be dependent on the abscisic acid (ABA) signaling pathway, which signifies the potential for these genes to be utilized within breeding frameworks aimed at increasing soybean resilience against salt stress. The results indicate future studies can benefit from the insights on GmERF13 signaling pathways to explore genetic variability and intrinsic plant mechanisms for combating environmental adversities.
Overall, the elucidation of GmERF13's functions not only enhances the scientific understandings of salt-mediated regulation but also suggests candidate genes for future molecular design and breeding. By targeting the GmERF13-GmLBD16a-GmEXP17 regulatory network, researchers can strategize bean cultivars optimized for performance even on saline soils.