Fine mapping of qAHPS07 and functional studies of AhRUVBL2 controlling pod size in peanut (Arachis hypogaea L.).

Cultivated peanut (Arachis hypogaea L.) is an important oil and cash crop. Pod size is one of the major traits determining yield and commodity characteristic of peanut. Fine mapping of quantitative trait locus (QTL) and identification of candidate genes associated with pod size are essential for genetic improvement and molecular breeding of peanut varieties. In this study, a major QTL related to pod size, qAHPS07, was fine mapped to a 36.46 kb interval on chromosome A07 using F2 , recombinant inbred line (RIL) and secondary F2 populations. qAHPS07 explained 38.6%, 23.35%, 37.48%, 25.94% of the phenotypic variation for single pod weight (SPW), pod length (PL), pod width (PW) and pod shell thickness (PST), respectively. Whole genome resequencing and gene expression analysis revealed that a RuvB-like 2 protein coding gene AhRUVBL2 was the most likely candidate for qAHPS07. Overexpression of AhRUVBL2 in Arabidopsis led to larger seeds and plants than the wild type. AhRUVBL2-silenced peanut seedlings represented small leaves and shorter main stems. Three haplotypes were identified according to three SNPs in the promoter of AhRUVBL2 among 119 peanut accessions. Among them, SPW, PW and PST of accessions carrying Hap_ATT represent 17.6%, 11.2% and 26.3% higher than those carrying Hap_GAC，respectively. In addition, a functional marker of AhRUVBL2 was developed. Taken together, our study identified a key functional gene of peanut pod size, which provides new insights into peanut pod size regulation mechanism and offers practicable markers for the genetic improvement of pod size-related traits in peanut breeding.

Genome-Wide Identification of Auxin Response Factors in Peanut (Arachis hypogaea L.) and Functional Analysis in Root Morphology.

Auxin response factors (ARFs) play important roles in plant growth and development; however, research in peanut (Arachis hypogaea L.) is still lacking. Here, 63, 30, and 30 AhARF genes were identified from an allotetraploid peanut cultivar and two diploid ancestors (A. duranensis and A. ipaensis). Phylogenetic tree and gene structure analysis showed that most AhARFs were highly similar to those in the ancestors. By scanning the whole-genome for ARF-recognized cis-elements, we obtained a potential target gene pool of AhARFs, and the further cluster analysis and comparative analysis showed that numerous members were closely related to root development. Furthermore, we comprehensively analyzed the relationship between the root morphology and the expression levels of AhARFs in 11 peanut varieties. The results showed that the expression levels of AhARF14/26/45 were positively correlated with root length, root surface area, and root tip number, suggesting an important regulatory role of these genes in root architecture and potential application values in peanut breeding.

Establishment and evaluation of a peanut association panel and analysis of key nutritional traits.

Breeding programs aim to improve the yield and quality of peanut (Arachis hypogaea L.); using association mapping to identify genetic markers linked to these quantitative traits could facilitate selection efficiency. A peanut association panel was established consisting of 268 lines with extensive phenotypic and genetic variation, meeting the requirements for association analysis. These lines were grown over 3 years and the key agronomic traits, including protein and oil content were examined. Population structure (Q) analysis showed two subpopulations and clustering analysis was consistent with Q-based membership assignment and closely related to botanical type. Relative Kinship (K) indicated that most of the panel members have no or weak familial relatedness, with 52.78% of lines showing K = 0. Linkage disequilibrium (LD) analysis showed a high level of LD occurs in the panel. Model comparisons indicated false positives can be effectively controlled by taking Q and K into consideration and more false positives were generated by K than Q. A preliminary association analysis using a Q + K model found markers significantly associated with oil, protein, oleic acid, and linoleic acid, and identified a set of alleles with positive and negative effects. These results show that this panel is suitable for association analysis, providing a resource for marker-assisted selection for peanut improvement.

The preventive effect of mussel oil on gestational diabetes mellitus in pregnant mice fed by a high-fat and high-sucrose diet.

The present study aimed to investigate the preventive effect of mussel oil (MO) on gestational diabetes mellitus (GDM) in mice fed by a high-fat and high-sucrose (HFHS) diet. Pregnant mice were allocated to four groups: normal diet + corn oil (CO), HFHS + CO, HFHS + fish oil (FO), and HFHS + MO. The total n-3 polyunsaturated fatty acids (PUFAs) in MO (51.30%) and FO (48.25%) were comparable (mainly C22:6n-3 and C20:5n-3). HFHS + MO and HHFS + FO had a significantly lower area under the curve (AUC) for the oral glucose tolerance test (OGTT) than the HFHS + CO group. The HFHS + MO group but not HFHS + FO group had a significantly lower AUC for the insulin tolerance test (ITT) than the HFHS + CO group. The HFHS + MO group had significantly lower homeostasis model assessment-insulin resistance (HOMA-IR) and fasting serum insulin than the HHFS + FO and HFHS + CO groups. Liver sphingosine kinase 1 (SphK1) was significantly higher, while SphK2, Akt, and P-Akt were significantly lower in the HFHS + CO group compared with the normal diet + CO group. The HFHS + MO group but not the HFHS + FO group had significantly higher SphK2, Akt, and P-Akt than the HFHS + CO group. SphK2 had a strong negative correlation with the AUC for the OGTT (r = -0.759, p = 0.001) and insulin tolerance test (ITT) (r = -0.637; p = 0.008), fasting serum insulin (r = -0.594, p = 0.015), fasting blood glucose (r = -0.587, p = 0.017) and HOMA-IR (r = -0.629, p = 0.009) and a strong positive correlation with Akt (r = 0.594, p = 0.015) and P-Akt (r = 0.676, p = 0.004). In conclusion, mussel oil improved glucose intolerance and insulin resistance during mice pregnancy, which was superior to the effects of fish oil.

Identification of Peanut Aux/IAA Genes and Functional Prediction during Seed Development and Maturation.

Auxin-responsive genes AUX/IAA are important during plant growth and development, but there are few relevant reports in peanut. In this study, 44 AhIAA genes were identified from cultivated peanut, of which 31 genes were expressed in seed at varying degrees. AhIAA-3A, AhIAA-16A and AhIAA-15B were up-regulated, while AhIAA-11A, AhIAA-5B and AhIAA-14B were down-regulated with seed development and maturation. The expression patterns of seven genes, AhIAA-1A, AhIAA-4A, AhIAA-10A, AhIAA-20A, AhIAA-1B, AhIAA-4B and AhIAA-19B, were consistent with the change trend of auxin, and expression in late-maturing variety LM was significantly higher than that in early-maturing EM. Furthermore, allelic polymorphism analysis of AhIAA-1A and AhIAA-1B, which were specifically expressed in seeds, showed that three SNP loci in 3'UTR of AhIAA-1A could effectively distinguish the EM- and LM- type germplasm, providing a basis for breeding markers development. Our results offered a comprehensive understanding of Aux/IAA genes in peanut and provided valuable clues for further investigation of the auxin signal transduction pathway and auxin regulation mechanism in peanut.