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Pod size is a key agronomic trait that influences peanut yield greatly. However, our understanding of the mechanisms underlying pod size is limited. In this study, we employed a segregating population derived from a cross between the small-pod line ND_S and the large-pod line ND_L to map quantitative trait loci (QTL) associated with pod size. Initial mapping performed using bulk segregant analysis revealed a candidate interval on chromosome A05 referred to as qPSW05. We refined this interval to a 256.9 kb genomic region using newly developed molecular markers. Through sequence and expression analyses, we identified the candidate gene AhXE45GC, which encodes an AN1 zinc finger protein. We discovered a 33-bp insertion in the intron of AhXE45GCin ND_S. Accessions that lack this insertion, such as ND_L, had significantly larger pods than those with the insertion, including ND_S. To facilitate marker-assisted selection for peanut pod size, we developed a molecular marker associated with this polymorphism. This marker could provide a valuable genetic resource for breeding high-yielding peanut varieties.

Peanut (Arachis hypogaeaL.) is an important oil crop. Oleic acid is a major factor that determines the quality of peanuts. Therefore, the high oleic and high oleic to linoleic acid ratio are the target traits in an advanced peanut breeding program. This study provided an extensive evaluation of the genetic and physical characteristics as well as disease resistance of 220 high oleic peanut varieties in China. Notably, these varieties clustered into five major categories based on their traits. A majority of these varieties have been bred using interspecific hybridization or selected from mutants of self-crossed parents, with the main parent varieties being Kaixuan 016 and CTWE. Analysis of disease resistance showed that most high oleic peanut varieties could resist two or three diseases. However, those varieties with resistance to multiple diseases were relatively scarce. Moreover, some high oleic peanut varieties showed no disease resistance or inadequate testing. The results further indicate that the genetic basis for high oleic peanut breeding is insufficient, highlighting the need for its further development. Importantly, our findings lay a critical foundation for future high oleic peanut breeding and promote better understanding of the genetic and trait diversity offered by these varieties.

Peanut (Arachis hypogaeaL.) is one of the most important oil crops in the world due to its lipid-rich seeds. Lipid accumulation and degradation play crucial roles in peanut seed maturation and seedling establishment, respectively. Here, we utilized lipidomics and transcriptomics to comprehensively identify lipids and the associated functional genes that are important in the development and germination processes of a large-seed peanut variety. A total of 332 lipids were identified; triacylglycerols (TAGs) and diacylglycerols were the most abundant during seed maturation, constituting 70.43 and 16.11%, respectively, of the total lipids. Significant alterations in lipid profiles were observed throughout seed maturation and germination. Notably, TAG (18:1/18:1/18:2) and (18:1/18:2/18:2) peaked at 23386.63 and 23392.43 nmol/g, respectively, at the final stage of seed development. Levels of hydroxylated TAGs (HO-TAGs) increased significantly during the initial stage of germination. Accumulation patterns revealed an inverse relationship between free fatty acids and TAGs. Lipid degradation was determined to be regulated by diacylglycerol acyltransferase, triacylglycerol lipase, and associated transcription factors, predominantly yielding oleic acid, linoleic acid, and linolenic acid. Collectively, the results of this study provide valuable insights into lipid dynamics during the development and germination of large-seed peanuts, gene resources, and guiding future research into lipid accumulation in an economically important crop.

Peanut (Arachis hypogaeaL.) bacterial wilt (BW), caused by Ralstonia solanacearum(RS), is a devastating soil-borne disease that poses a significant threat to peanut yield and quality. Nucleotide-binding leucine-rich repeat (NBS-LRR) proteins are a class of plant-specific immune receptors that recognize pathogen-secreted effector molecules and activate immune responses to resist pathogen infections. However, the precise functions of AhCNgenes (CN is a class of NLR genes lacking LRR structural domains) in peanut plants are not fully understood. In this study, a total of 150 AhCNgenes were identified and classified into nine subfamilies based on a systematic phylogenetic analysis. The AhCNgenes showed highly conserved structural features; promoter cis-elements indicated involvement in plant hormone signaling and defense responses. Following inoculation with RS, the highly resistant peanut variety ‘H108’ significantly outperformed the susceptible variety ‘H107’ in physiological indicators such as plant height, main stem diameter, and fresh weight, likely due to inhibition of bacterial proliferation and diffusion in the stem vascular bundle. AhCN34was found to be significantly upregulated in H108 compared to H107 during plant infection and in response to treatment with each of three plant hormones. Importantly, AhCN34overexpression in peanut leaves enhanced their resistance to BW. These findings demonstrate the great potential of AhCN34for applications in peanut resistance breeding. Our identification and characterization of AhCNgenes provide insights into the mechanisms underlying peanut BW resistance and inform future research into genetic methods of improving peanut BW resistance.

Peanut seeds have a high oil content making them an important oil crop. During development and germination, seeds undergo complex dynamic and physiological changes. Changes in lipid metabolism and underlying mechanisms during seed development have been studied extensively by DNA and RNA sequencing; however, there are few studies on dynamic changes of proteomics during peanut seed development and germination. In this study, proteomic analyses were carried out 20, 40, 60, and 80 days after pollination and 5, 10, 20, and 30 days after germination using isobaric tags for relative and absolute quantitation (iTRAQ) technology to determine the protein profiles of lipid dynamics during peanut seed development and postgermination. A total of 5712 of 8505 proteins were identified, quantified, and divided into 23 functional groups, the largest of which was metabolism-related. Further analyses of the proteins and their pathways revealed initiation of fatty acid accumulation at early stages after flowering, while lipid degradation occurred largely through the lipoxygenase-dependent pathway. Protein expression patterns related to lipid accumulation and degradation were also verified at transcript levels using quantitative real-time polymerase chain reaction. The proteome profiles determined here will significantly enrich our understanding of the process of lipid accumulation and degradation and the dynamic changes in metabolic networks during peanut development.

Background: Three-dimensional (3D) chromatin organization provides a critical foundation to investigate gene expression regulation and cellular homeostasis. Results: Here, we present the first 3D genome architecture maps in wild type and mutant allotetraploid peanut lines, which illustrate A/B compartments, topologically associated domains (TADs), and widespread chromatin interactions. Most peanut chromosomal arms (52.3%) have active regions (A compartments) with relatively high gene density and high transcriptional levels. About 2.0% of chromosomal regions switch from inactive to active (B-to-A) in the mutant line, harboring 58 differentially expressed genes enriched in flavonoid biosynthesis and circadian rhythm functions. The mutant peanut line shows a higher number of genome-wide cis-interactions than its wild-type. The present study reveals a new TAD in the mutant line that generates different chromatin loops and harbors a specific upstream AP2EREBP-binding motif which might upregulate the expression of the GA2oxgene and decrease active gibberellin (GA) content, presumably making the mutant plant dwarf. Conclusions: Our findings will shed new light on the relationship between 3D chromatin architecture and transcriptional regulation in plants.

Peanut (Arachis hypogeaL.) bacterial wilt (BW) is a devastating disease caused by Ralstonia solanacearumthat results in severe yield and quality losses. Plant defensins are short cysteine-rich peptides with antimicrobial activity. The role of defensin genes (AhDef) in peanut is unclear. A genome-wide investigation of AhDefgenes was undertaken, and 12 identified AhDefgenes were classified into two groups containing the gamma-thionin domain formed by four disulfide pairs: Cys1-Cys8, Cys2-Cys5, Cys3-Cys6, and Cys4-Cys7. In silicoanalysis revealed that AhDefgenes showed highly conserved architectural features and contained cis-elements associated with phytohormone signaling and defense responses. A highly resistant cultivar, H108 (R) and a susceptible accession, H107 (S) were tested by R. solanacearuminoculation. H108 (R) showed fewer symptoms than H107 (S) owing to inhibition of bacterial reproduction and spread in the vascular bundles of roots and stems. In a transcriptomic expression profile, AhDefgenes, particularly AhDef1.6and AhDef2.2, were up-regulated in H108 (R) compared with H107 (S) under R. solanacearuminfection and phytohormone treatment. Subcellular localization showed that the AhDef1.6 and AhDef2.2 proteins were both expressed specifically on the plasma membrane. Overexpression of protein fusion AhDef2.2-YFP in Nicotiana benthamianaand peanut leaves increased resistance to R. solanacearum, suggesting its role in response to BW infection. AhDef2.2may be valuable for peanut resistance breeding.