Auxin plays an important role in regulating plant development, and Auxin/indole acetic acid (Aux/IAA) is a type of auxin-responsive gene and plays an important role in auxin signaling; to date, although 29 Aux/IAA proteins have been reported in Abrabidopsis thaliana, only parts of the Aux/IAA family gene functions have been identified. We previously reported that a bud sport of ‘Longfeng’ (LF) apple (Malus domestica), named ‘Grand longfeng’ (GLF), which showed a larger fruit size than LF, has lower expression of MdAux/IAA2. In this study, we identified the function of the MdAux/IAA2 gene in apple fruit size difference using Agrobacterium-mediated genetic transformation. Overexpression of MdAux/IAA2 decreased the apple flesh callus increment and caused a smaller globular cell size. In addition, overexpression of MdAux/IAA2 in GLF fruit resulted in the reduction of apple fruit size, weight, and cell size, while silencing MdAux/IAA2 in LF apple fruit resulted in an increase in apple fruit weight and cell size. We suggest that the high auxin content depressed the expression of MdAux/IAA2, and that the downregulated expression of MdAux/IAA2 led to the formation of GLF. Our study suggests a mechanism for fruit size regulation in plants and we will explore the transcription factors functioning in this process in the future.

Total flower and pod numbers (TFPN) and effective pod numbers per plant (PNPP) are among the most important agronomic traits for soybean production. However, the underlying genetic mechanism remains unclear. In this study, we constructed a recombinant inbred line population derived from a cross between JY73 (high TFPN) and TJSLH (low TFPN) to map loci for the two traits. In total, six QTL for TFPN and five QTL for PNPP were identified, among which a QTL on chromosome 4, named qFPN4, explained 9.2% and 9.6% of the phenotypic variation of TFPN and PNPP, respectively. Analysis of residual heterozygous lines for qFPN4 indicated that TFPN or PNPP was controlled by a single dominant gene at this locus and delimited the QTL into a ~2.62 Mb interval which tightly linked to an Indel marker C1-5. This mapping result was further confirmed by bulked segregant analysis (BSA) of the near isogenic lines. The genome-sequencing-based BSA also identified eight candidate genes carrying nonsynonymous SNPs and/or Indels; two genes, Glyma.04G176600 and Glyma.04G178900, were nominated as the most promising genes for qFPN4 based on additional expression and function analysis. These results improve our understanding of the genetic mechanism of TFPN and PNPP and indicate the potential for soybean yield improvement.

Fruit size is a key economic trait in horticultural crops, determined by an integrated network of genetic, hormonal, epigenetic, and environmental factors. This review synthesizes recent advances in understanding this regulation. Genetically, key quantitative trait loci (QTLs) such as fw2.2, fw3.2, FAS, and LC control cell number and organ size. Hormones including auxin, gibberellin, cytokinin, and brassinosteroid regulate cell division and expansion. Transcription factors (e.g., YABBY, WOX families) and epigenetic mechanisms (DNA methylation, histone modifications, endoreduplication) provide additional regulatory layers. Environmental factors (light, temperature, water, nutrition) and cultivation practices (pruning, thinning) ultimately shape the final fruit phenotype. Emerging technologies like multi-omics, CRISPR-Cas9 gene editing, and artificial intelligence offer powerful tools for future research and molecular breeding, which aim to decode the complex regulatory network and enhance crop yield and quality.

Research on structural variations in the field of crop genetics has expanded with the rapid development of genome sequencing technologies. As an important aspect of genomic variations, structural variations have a profound impact on the genetic characteristics of crops and significantly affect their key agronomic traits, such as yield, quality, and disease and stress resistance—by changing the gene arrangement order, copy number, and the positions of regulatory elements. Compared with single-nucleotide polymorphisms, structural variations present a diverse range of types, including deletions, duplications, inversions, and translocations, and their impacts are more extensive and profound. However, research on structural variations in crops still faces many challenges, for example those relating to different ploidy levels, genome repetitiveness, and their associations with phenotypes. Nevertheless, breakthroughs in long-read sequencing technologies and the integration of multi-omics data offer hope for solving these problems. A deep understanding of the impact of structural variations on crops is of great significance for accurately analyzing the evolutionary history of crops and guiding modern crop breeding, and is expected to provide strong support for global food security and the sustainable development of agriculture.

Saline–alkali environments restrict soybean production in China. Wild soybean genes can be used to improve the alkaline tolerance of cultivated soybean in molecular breeding. The expansin protein family promotes cell wall expansion. In this study, the relative expression levels of expansin family genes in wild soybean treated with 50 mM NaHCO₃ were measured at 0, 3, 6, and 12 h, and the relative expression of GsEXPA8 was found to be higher at 12 h. Wild soybean was treated with abscisic acid (ABA), indole-3-acetic acid (IAA), gibberellic acid (GA), and jasmonic acid (JA), and GsEXPA8 was found to respond to ABA and IAA signals. Sequence analysis shows that GsEXPA8 has DPBB_EXPA and expansin domains. Subcellular localization analysis shows that GsEXPA8 was localized in the cytoplasm in protoplasts and the cell membrane or wall in tobacco, indicating that it has nuclear membrane localization signals. GsEXPA8 overexpression reduced the malondialdehyde content in transgenic plants treated with NaHCO₃ and increased peroxidase activity before treatment. After the transformation of soybean roots from hair roots, GsEXPA8 was found to be expressed in the outer root cells and promote the development of thicker, shorter roots, thereby improving the plant’s alkaline tolerance. Stable GsEXPA8 transformation improved saline alkaline tolerance via the regulation of the alkali stress-related genes GmKIN1, GmRD22, GmDnaJA6, GmNFYC1, and GmMYB14. These findings provide support for further research on alkali-tolerance regulation pathways and molecular breeding for alkali tolerance.

Soil alkalinity and heavy metal toxicity are major abiotic stresses that severely limit plant growth and crop productivity. Wild soybean (Glycine soja) exhibits strong alkaline tolerance, making it a valuable genetic resource for improving cultivated soybean. Previous studies identified Gshdz4 and GsNAC019 as key alkaline-tolerant transcription factors, and GsEXPA8 as an alkaline-tolerant expansin protein. This study establishes a hierarchical "nucleus-nucleus-membrane" regulatory model in wild soybean, wherein the nuclear master transcription factor Gshdz4 transcriptionally upregulates GsNAC019, which in turn activates the expression of the plasma membrane-localized expansin GsEXPA8, collectively enhancing alkaline tolerance. We further investigated the role of Gshdz4 in conferring resistance to combined sodium bicarbonate and cadmium chloride stress in soybean. Through integrated RNA-seq and CUT&Tag-seq analyses, we identified Gshdz4 as a direct binder and regulator of diverse stress-responsive genes-including GmDEAH5, GmHSP22.3, GmACR4, and GmATG1c. Under alkaline stress, Gshdz4 modulates GmSLX8, GmSF3, and GmPP4; under cadmium stress, it regulates GmGMFL01 and GmUNC, establishing a broad-spectrum defense mechanism. Additional targets encompass splicing factors, heat shock proteins, ABA signaling components, and ethylene-responsive factors. GO and KEGG enrichment analyses confirmed that Gshdz4 participates in multiple hormonal pathways (ABA, IAA, ET, JA) and stress response signaling. Our findings revealed Gshdz4 as a master transcriptional regulator under multiple stresses and provide a theoretical foundation for molecular breeding strategies to enhance soybean resilience.