Legumes can utilize atmospheric nitrogen via symbiotic nitrogen fixation, but this process is inhibited by high soil inorganic nitrogen. So far, how high nitrogen inhibits N₂ fixation in mature nodules is still poorly understood. Here we construct a co-expression network in soybean nodule and find that a dynamic and reversible transcriptional network underlies the high N inhibition of N₂ fixation. Intriguingly, several NAC transcription factors (TFs), designated as Soybean Nitrogen Associated NAPs (SNAPs), are amongst the most connected hub TFs. The nodules of snap1/2/3/4 quadruple mutants show less sensitivity to the high nitrogen inhibition of nitrogenase activity and acceleration of senescence. Integrative analysis shows that these SNAP TFs largely influence the high nitrogen transcriptional response through direct regulation of a subnetwork of senescence-associated genes and transcriptional regulators. We propose that the SNAP-mediated transcriptional network may trigger nodule senescence in response to high nitrogen.

Prime editing (PE) enables precise genome modifications to mammalian cells and monocot staple crops, but remains relatively challenging in dicot plants. Here, we develop a Flanking-Nicks Prime Editor (FLICK-PE) system that boosts editing efficiency in soybean and tobacco. We show that optimization for PE by adding a nicking sgRNA could dramatically enhance intended-editing efficiency in soybean. Inspired by this observation, we design a FLICK-PE strategy to confer a pair of nicks flanking the target site. In soybean, FLICK-PE achieves on average a 15.7-fold increase in intended-editing efficiency compared to PE2, and a 2.2-fold increase compared to PE3. Using FLICK-PE, we efficiently engineer glyphosate resistance in soybean by introducing TAP–IVS mutations in EPSPS1a , achieving three amino-acid substitutions and an intended editing efficiency of 21.1%. This approach yields stable edited soybean varieties with vigorous glyphosate tolerance and minimal growth penalties in a field trial. FLICK-PE also demonstrates efficacy in tobacco, underscoring its broad applicability and versatility for rapid, precision breeding in agriculturally vital crops.

Modern agriculture currently demands higher standards for the simultaneous improvement of crop yield, quality and stress resistance. However, traditional crop breeding methods can no longer meet the needs of modern agricultural development. Improving a single trait is no longer sufficient to meet the multifaceted demands of modern agricultural production and consumer expectations. Multiple traits breeding has increasingly become a key objective in current crop breeding. Over the past decade, CRISPR/Cas9-based multiplex genome editing (MGE) has enabled efficient pyramiding and precise regulation of multiple traits via targeted editing of multiple gene loci, revolutionizing crop breeding. In this review, we briefly describe the core CRISPR/Cas-based MGE strategies and technical workflows, and thoroughly discuss the practical outcomes of MGE applications in various fields, such as enhancing crop stress resistance, increasing yield and improving quality. This review aims to provide a summary and theoretical reference for crop breeding, as well as open up new ideas for achieving different breeding goals.