Yupeng Cai

Flowering time and drought resistance are two pivotal agronomic traits in soybean. Elucidating coregulatory modules that link soybean flowering and drought response is essential for constructing comprehensive molecular maps of trait coupling. In this study, we identified that MORN-MOTIF REPEAT PROTEIN REGULATING FLOWERING LIKE (GmMRFL) gene functions as a bifunctional regulator that concurrently promotes floral transition by upregulating the expression of Flowering Locus T (FT) genes and enhances drought resilience through stomatal adjustment, accompanied by abscisic acid (ABA) signaling and reactive oxygen species (ROS) suppression. In addition, the transcription factor AP2/ETHYLENE-RESPONSIVE FACTOR 011 (GmERF011) specifically binds to and activates the Hap1 promoter variant of GmMRFL, thereby promoting the upregulation of GmMRFL expression. Phenotypic analyses of hairy roots validated the role of GmERF011 in enhancing drought tolerance in soybean. Integrated molecular analyses revealed that GmMRFL interacts with ANKYRIN REPEAT DOMAIN PROTEIN 2 (GmANK2). These findings demonstrate that GmMRFL serves as a molecular hub that coordinately modulates photoperiod-dependent flowering regulation and drought adaptation, thereby establishing it as a prime target for multi-trait engineering in precision crop breeding.

Sugars serve as primary energy sources and key essential signaling molecules, playing pivotal roles in regulating plant growth and development. Crop yield is tightly linked to the efficient partitioning of photoassimilates from source leaves to sink organs. This process is intricately regulated by sugar sensing and transport systems, which orchestrate the dynamic source–sink balance by modulating phloem loading, long-distance translocation, and sink unloading. While substantial progress has been made in deciphering these mechanisms in model organisms, a comprehensive understanding of the regulatory network in soybean—a globally significant crop with unique plant architecture in which leaves, inflorescences, and pods are borne on nodes—remains elusive. The emergence of gene-editing tools, notably CRISPR/Cas9, offers powerful tools for dissecting redundant transporter families and targeted engineering of key regulatory nodes. This review synthesizes the current understanding of the molecular networks governing sugar perception and long-distance transport, with a specific focus on soybean. It further explores the utility of gene editing in accelerating the functional characterization of critical components and highlights potential molecular targets for manipulating source–sink dynamics to enhance soybean yield.

Soybean (Glycine max) is a globally important crop; however, its productivity is severely impacted by phosphorus (P) deficiency. Understanding the transcriptional regulation of low P (LP) response mechanisms is essential for enhancing soybean P use efficiency. In this study, we found that the Nuclear Factor-Y (NF-Y) transcription factor GmNF-YC4, in addition to its previously discovered role in regulating flowering time, possesses another functions in modulating root morphology and P uptake. Knockout of GmNF-YC4 notably boosted root proliferation and P uptake while also influencing the expression of genes related to LP stress. GmNF-YC4 acts as a specific DNA-binding transcriptional repressor, modulating the expression of the soybean α-EXPANSIN 7 (GmEXPA7) gene, which encodes a cell wall-loosening factor, through direct binding to its promoter region. Further investigation revealed that GmEXPA7 expression is predominantly root-specific and induced by LP. Moreover, overexpression of GmEXPA7 in soybean hairy roots enhanced LP tolerance by stimulating root growth and P uptake. We further screened and obtained more potential target genes of GmNF-YC4 via DNA affinity purification sequencing, including those related to LP stress. These findings underscore the pivotal role of the GmNF-YC4-GmEXPA7 module as a key regulator in mitigating LP stress in soybean.

Flowering time and growth period are key agronomic traits which directly affect soybean (Glycine max (L.) Merr.) adaptation to diverse latitudes and farming systems. The FLOWERING LOCUS T (FT) homologs GmFT2a and GmFT5a integrate multiple flowering regulation pathways and significantly advance flowering and maturity in soybean. Pinpointing the genes responsible for regulating GmFT2a and GmFT5a will improve our understanding of the molecular mechanisms governing growth period in soybean. In this study, we identified the Nuclear Factor Y‐C (NFY‐C) protein GmNF‐YC4 as a novel flowering suppressor in soybean under long‐day (LD) conditions. GmNF‐YC4 delays flowering and maturation by directly repressing the expression of GmFT2a and GmFT5a. In addition, we found that a strong selective sweep event occurred in the chromosomal region harboring the GmNF‐YC4 gene during soybean domestication. The GmNF‐YC4^Hap3 allele was mainly found in wild soybean (Glycine soja Siebold & Zucc.) and has been eliminated from G. max landraces and improved cultivars, which predominantly contain the GmNF‐YC4^Hap1 allele. Furthermore, the Gmnf‐yc4 mutants displayed notably accelerated flowering and maturation under LD conditions. These alleles may prove to be valuable genetic resources for enhancing soybean adaptability to higher latitudes.

Plants can sense the photoperiod to flower at the right time. As a sensitive short‐day crop, soybean (Glycine max) flowering varies greatly depending on photoperiods, affecting yields. Adaptive changes in soybeans rely on variable genetic loci such as E1 and FLOWERING LOCUS T orthologs. However, the precise coordination and control of these molecular components remain largely unknown. In this study, we demonstrate that GmFT5b functions as a crucial factor for soybean flowering. Overexpressed or mutated GmFT5b resulted in significantly early or later flowering, altering expression profiles for several downstream flowering‐related genes under a long‐day photoperiod. GmFT5b interacts with the transcription factor GmFDL15, suggesting transcriptional tuning of flowering time regulatory genes via the GmFT5b/GmFDL15 complex. Notably, GmFT5a partially compensated for GmFT5b function, as ft5a ft5b double mutants exhibited an enhanced late‐flowering phenotype. Association mapping revealed that GmFT5b was associated with flowering time, maturity, and geographical distribution of soybean accessions, all associated with the E1 locus. Therefore, GmFT5b is a valuable target for enhancing regional adaptability. Natural variants or multiple mutants in this region can be utilized to generate optimized soybean varieties with precise flowering times.

Seed size is a critical agronomic trait that influences the yield and appearance quality of soybeans, making it a primary breeding objective with significant economic value. While the molecular mechanisms that regulate soybean seed size remain largely unknown, several functional molecular targets have been applied in breeding to create larger grain size materials. In this study, we utilized the CRISPR/Cas9 system to induce the targeted mutagenesis of GmEOD1, which encodes the E3 ubiquitin ligase. The resulting homozygous soybean mutant of GmEOD1 exhibited larger seed size and 100-seed weight, with no significant change in the average seed weight per plant. The sum of crude protein and oil content increased significantly in mutants while fatty acid composition remained unchanged. We identified six haplotypes among 156 soybean cultivars, with Hap1 and Hap2 representing the majority of cultivars with relatively higher 100-seed weight, suggesting that sequence variations of GmEOD1 may correlate with seed weight. Transcriptomic analysis across five stages of seed development revealed that stages one–three mainly focused on cell cycle, growth, wall synthesis and modification, photosynthesis, and sugar metabolism; promoting cell growth, reproduction, and carbon accumulation; and providing key intermediates for substance synthesis. Stages four–five focused on polysaccharide catabolism, xylan metabolism, and nutrient pool activity, promoting the accumulation of dry matter, such as sugars, proteins, and lipids in seeds. Weighted gene co-expression network analysis (WGCNA) of modules related to seed size revealed 13 hub genes involved in seed development regulation. This study provides a valuable theoretical basis and excellent opportunities for genetic editing of germplasm cells with subsequent molecular soybean seed size breeding, facilitating easier seed selection to improve soybean quality.

Human existence is intricately intertwined with crops, which can serve as abundant sources of food, feed, and all kinds of consumable resources