Search

AhFAD2 is a key enzyme catalyzing the conversion of oleic acid into linoleic acid. The high oleic acid characteristic of peanut mainly comes from the homozygous recessive mutation of

Seed size is a key factor affecting crop yield and a major agronomic trait concerned in peanut (Arachis hypogaea L.) breeding. However, little is known about the regulation mechanism of peanut seed size. In the present study, a peanut small seed mutant1 (ssm1) was identified through irradiating peanut cultivar Luhua11 (LH11) using 60Coγ ray. Since the globular embryo stage, the embryo size of ssm1 was significantly smaller than that of LH11. The dry seed weight of ssm1 was only 39.69% of the wild type LH14. The seeds were wrinkled with darker seed coat. The oil content of ssm1 seeds were also decreased significantly. Seeds of ssm1 and LH11 were sampled 10, 20, and 40 days after pegging (DAP) and were used for RNA-seq. The results revealed that genes involved in plant hormones and several transcription factors related to seed development were differentially expressed at all three stages, especially at DAP10 and DAP20. Genes of fatty acid biosynthesis and late embryogenesis abundant protein were significantly decreased to compare with LH11. Interestingly, the gene profiling data suggested that PKp2 and/or LEC1 could be the key candidate genes leading to the small seed phenotype of the mutant. Our results provide valuable clues for further understanding the mechanisms underlying seed size control in peanut.

Background Cistanche as a famous tonic Chinese traditional medicine, is known as "desert ginseng". Its dried fleshy stem is a crucial tonic in Chinese traditional medicine, and the main active pharmacodynamic components are phenylethanol glycosides. Cistanche tubulosa is more suitable for cultivation and extracting active ingredients because it produces higher level of phenylethanol glycosides than C. deserticola. The molecular regulation of the phenylethanol glycosides is not clear, partially due to the lack of genomic and transcriptomic resources in C. tubulosa. Results In this study, we performed the full-length transcriptome sequencing and gene expression profiling of C. tubulosa using PacBio combined with BGISEQ-500 RNA-seq technology. Totally, 237,772 unique transcripts were obtained, the transcript lengths ranging from 199 bp to 31,857 bp, and the N50 length was 1,797 bp. Among the unique transcripts, 188,135 (79.12%) transcripts were annotated. Interestingly, 1080 transcripts were annotated as 22 enzymes related to PhGs biosynthesis. We measured the content of echinacoside, acteoside and total PhGs at two development stages, and found that the content of PhGs was 46.74% of dry matter in young fleshy stem (YS1) and then decreased to 31.22% at the harvest stage (HS2). To compare with YS1, 13,631 genes were up-regulated, and 15,521 genes were down regulated in HS2. Many differentially expressed genes (DEGs) were identified to be involved in phenylpropanoid biosynthesis pathway, phenylalanine metabolism pathway and tyrosine metabolism pathway between YS1 and HS2. Conclusions Based on these results, we proposed a potential model for phenylethanol biosynthesis regulation. This is the first report of transcriptome study of C. tubulosa which provided the foundation for understanding of PhGs biosynthesis regulation.

Lateral branch angle (LBA), or branch habit, is one of the most important agronomic traits in peanut. To date, the underlying molecular mechanisms of LBA have not been elucidated in peanut. To acquire the differentially expressed genes (DEGs) related to LBA, a TI population was constructed through the hybridization of a bunch-type peanut variety Tifrunner and prostrate-type Ipadur. We report the identification of DEGs related to LBA by sequencing two RNA pools, which were composed of 45 F3 lines showing an extreme opposite bunch and prostrate phenotype. We propose to name this approach Bulk RNA-sequencing (BR-seq) as applied to several plant species. Through BR-seq analysis, a total of 3083 differentially expressed genes (DEGs) were identified, including 13 gravitropism-related DEGs, 22 plant hormone-related DEGs, and 55 transcription factors-encoding DEGs. Furthermore, we also identified commonly expressed alternatively spliced (AS) transcripts, of which skipped exon (SE) and retained intron (RI) were most abundant in the prostrate and bunch-type peanut. AS isoforms between prostrate and bunch peanut highlighted important clues to further understand the post-transcriptional regulatory mechanisms of branch angle regulation. Our findings provide not only important insights into the landscape of the regulatory pathway involved in branch angle formation but also present practical information for peanut molecular breeding in the future.

The candidate gene AhLBA1 controlling lateral branch angel of peanut was fine-mapped to a 136.65-kb physical region on chromosome 15 using the BSA-seq and QTL mapping. Lateral branch angel (LBA) is an important plant architecture trait of peanut, which plays key role in lodging, peg soil penetration and pod yield. However, there are few reports of fine mapping and quantitative trait loci (QTLs)/cloned genes for LBA in peanut. In this project, a mapping population was constructed using a spreading variety Tifrunner and the erect variety Fuhuasheng. Through bulked segregant analysis sequencing (BSA-seq), a major gene related to LBA, named as AhLBA1, was preliminarily mapped at the region of Chr.15: 150-160 Mb. Then, using traditional QTL approach, AhLBA1 was narrowed to a 1.12 cM region, corresponding to a 136.65-kb physical interval of the reference genome. Of the nine genes housed in this region, three of them were involved in hormone metabolism and regulation, including one "F-box protein" and two "2-oxoglutarate (2OG) and Fe(II)-dependent oxygenase (2OG oxygenase)" encoding genes. In addition, we found that the level of some classes of cytokinin (CK), auxin and ethylene showed significant differences between spreading and erect peanuts at the junction of main stem and lateral branch. These findings will aid further elucidation of the genetic mechanism of LBA in peanut and facilitating marker-assisted selection (MAS) in the future breeding program.

Peanut is one of the most important oil crops in the world, the growth and productivity of which are severely affected by salt stress. 24-epibrassinolide (EBL) plays an important role in stress resistances. However, the roles of exogenous EBL on the salt tolerance of peanut remain unclear. In this study, peanut seedlings treated with 150 mM NaCl and with or without EBL spray were performed to investigate the roles of EBL on salt resistance. Under 150 mM NaCl conditions, foliar application of 0.1 µM EBL increased the activity of catalase and thereby could eliminate reactive oxygen species (ROS). Similarly, EBL application promoted the accumulation of proline and soluble sugar, thus maintaining osmotic balance. Furthermore, foliar EBL spray enhanced the total chlorophyll content and high photosynthesis capacity. Transcriptome analysis showed that under NaCl stress, EBL treatment up-regulated expression levels of genes encoding peroxisomal nicotinamide adenine dinucleotide carrier (PMP34), probable sucrose-phosphate synthase 2 (SPS2) beta-fructofuranosidase (BFRUCT1) and Na+/H+ antiporters (NHX7 and NHX8), while down-regulated proline dehydrogenase 2 (PRODH). These findings provide valuable resources for salt resistance study in peanut and lay the foundation for using BR to enhance salt tolerance during peanut production.