134 research outputs found
Molecular cloning and characterization of an acyl-ACP thioesterase gene (AhFatB1) from allotetraploid peanut (Arachis hypogaea L.)
Acyl-acyl carrier protein (ACP) thioesterase is a nuclear encoded plastid localized enzyme which plays an essential role in chain termination during de novo fatty acid synthesis in plant. FatB genes coding for this enzyme from a variety of plant species have been isolated and characterized. However, there are few reports on such genes in peanut (Arachis hypogaea), an important edible and oilseed crop. In this study, full-length cDNA of an acyl-acyl carrier protein thioesterase (EC 3.1.2.14), designated as AhFatB1, was isolated from peanut cDNA libraries. The putative open reading frames consist of 1239 bp with five introns spliced from the corresponding genomic sequence, encoding a 413 amino acid protein, two homologous genes, AhFatB1A and AhFatB1B, with sequence difference at the 5’ non-coding regions were characterized at the nucleotide level from different cultivated peanut genotypes, and the two genes have their origin in different diploid progenitor which was evidenced by the characterization of AhFatB1 genes from Arachis duranensis and Arachis ipaensis, the putative A-genome donor and B-genome donor respectively. AhFatB1 genes are constitutively expressed in peanut tissues and the total FatB1 transcript accumulations are temporally regulated during peanut seed development.Keywords: Peanut thioesterase, palmitic acid oilsee
The emerging oilseed crop Sesamum indicum enters the “Omics” era
Sesame (Sesamum indicum L.) is one of the oldest oilseed crops widely grown in Africa and Asia for its high-quality nutritional seeds. It is well adapted to harsh environments and constitutes an alternative cash crop for smallholders in developing countries. Despite its economic and nutritional importance, sesame is considered as an orphan crop because it has received very little attention from science. As a consequence, it lags behind the other major oil crops as far as genetic improvement is concerned. In recent years, the scenario has considerably changed with the decoding of the sesame nuclear genome leading to the development of various genomic resources including molecular markers, comprehensive genetic maps, high-quality transcriptome assemblies, web-based functional databases and diverse daft genome sequences. The availability of these tools in association with the discovery of candidate genes and quantitative trait locis for key agronomic traits including high oil content and quality, waterlogging and drought tolerance, disease resistance, cytoplasmic male sterility, high yield, pave the way to the development of some new strategies for sesame genetic improvement. As a result, sesame has graduated from an “orphan crop” to a “genomic resource-rich crop.” With the limited research teams working on sesame worldwide, more synergic efforts are needed to integrate these resources in sesame breeding for productivity upsurge, ensuring food security and improved livelihood in developing countries. This review retraces the evolution of sesame research by highlighting the recent advances in the “Omics” area and also critically discusses the future prospects for a further genetic improvement and a better expansion of this crop. (Résumé d'auteur
Insight into the AP2/ERF transcription factor superfamily in sesame and expression profiling of DREB subfamily under drought stress
Background. Sesame is an important oilseed crop mainly grown in inclement areas with high temperatures and frequent drought. Thus, drought constitutes one of the major constraints of its production. The AP2/ERF is a large family of transcription factors known to play significant roles in various plant processes including biotic and abiotic stress responses. Despite their importance, little is known about sesame AP2/ERF genes. This constitutes a limitation for drought-tolerance candidate genes discovery and breeding for tolerance to water deficit. Results. One hundred thirty-two AP2/ERF genes were identified in the sesame genome. Based on the number of domains, conserved motifs, genes structure and phylogenetic analysis including 5 relatives species, they were classified into 24 AP2, 41 DREB, 61 ERF, 4 RAV and 2 Soloist. The number of sesame AP2/ERF genes was relatively few compared to that of other relatives, probably due to gene loss in ERF and DREB subfamilies during evolutionary process. In general, the AP2/ERF genes were expressed differently in different tissues but exhibited the highest expression levels in the root. Mostly all DREB genes were responsive to drought stress. Regulation by drought is not specific to one DREB group but depends on the genes and the group A6 and A1 appeared to be more actively expressed to cope with drought. Conclusions. This study provides insights into the classification, evolution and basic functional analysis of AP2/ERF genes in sesame which revealed their putative involvement in multiple tissue-/developmental stages. Out of 20 genes which were significantly up- /down-regulated under drought stress, the gene AP2si16 may be considered as potential candidate gene for further functional validation as well for utilization in sesame improvement programs for drought stress tolerance. (Résumé d'auteur
Simple sequence repeat (SSR)-based diversity analysis of groundnut (Arachis hypogaea L.) germplasm resistant to bacterial wilt
Groundnut is one of the most important oilseed crops in the world. Bacterial wilt, caused by Ralstonia solanacearum E. F. Smith, is one of the major biotic constraints to groundnut production particularly in South-East Asia and East Africa. Several sources of resistance to bacterial wilt have been identified through field screening of groundnut germplasm. The aim of the present study was to quantify the genetic diversity among selected bacterial wilt-resistant lines, in comparison with the levels of variation observable within the cultivated A. hypogaea gene pool. Thirty-two SSR markers were used to assess the degree of molecular polymorphism between 46 selected genotypes revealing 107 alleles, of which 101 (99.4%) were polymorphic with gene diversity scores ranging from 0.103 to 0.669, averaging 0.386. Cluster and multidimensional scaling analysis revealed two distinct groups within the germplasm broadly corresponding to the two subspecies (hypogaea and fastigiata) of A. hypogaea. However, accessions of varieties peruviana and aequatoriana grouped together with the varieties from subsp. hypogaea, rather than grouping with the other varieties of subsp. fastigiata. Analysis of molecular variance (AMOVA) revealed that 15% of the total observed variation was accounted for by disease response groups. This analysis will be useful in the selection of parental genotypes for mapping populations and breeding programmes attempting to broaden the genetic base of future groundnut cultivars. In particular, this opens up significant opportunities for the development of intraspecific mapping populations that will be highly relevant to modern groundnut breeding programmes
Development of a High-Density Genetic Map Based on Specific Length Amplified Fragment Sequencing and Its Application in Quantitative Trait Loci Analysis for Yield-Related Traits in Cultivated Peanut
High-density genetic maps (HDGMs) are very useful for genomic studies and quantitative trait loci (QTL) mapping. However, the low frequency of DNA polymorphisms in peanut has limited the quantity of available markers and hindered the construction of a HDGM. This study generated a peanut genetic map with the highest number of high-quality SNPs based on specific locus amplified fragment sequencing (SLAF-seq) technology and a newly constructed RIL population (“ZH16” × “sd-H1”). The constructed HDGM included 3,630 SNP markers belonging to 2,636 bins on 20 linkage groups (LGs), and it covers 2,098.14 cM in length, with an average marker distance of 0.58 cM. This HDGM was applied for the following collinear comparison, scaffold anchoring and analysis of genomic characterization including recombination rates and segregation distortion in peanut. For QTL mapping of investigated 14 yield-related traits, a total of 62 QTLs were detected on 12 chromosomes across 3 environments, and the co-localization of QTLs was observed for these traits which were significantly correlated on phenotype. Two stable co-located QTLs for seed- and pod-related traits were significantly identified in the chromosomal end of B06 and B07, respectively. The construction of HDGM and QTL analysis for yield-related traits in this study provide useful information for fine mapping and functional analysis of genes as well as molecular marker-assisted breeding
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A Major and Stable QTL for Bacterial Wilt Resistance on Chromosome B02 Identified Using a High-Density SNP-Based Genetic Linkage Map in Cultivated Peanut Yuanza 9102 Derived Population
Bacterial wilt (BW) is one of the important diseases limiting the production of peanut (Arachis hypogaea L.) worldwide. The sufficient precise information on the quantitative trait loci (QTL) for BW resistance is essential for facilitating gene mining and applying in molecular breeding. Cultivar Yuanza 9102 is BW resistant, bred from wide cross between cultivated peanut Baisha 1016 and a wild diploid peanut species A. chacoense with BW resistance. In this study, we aim to map the major QTLs related to BW-resistance in Yuanza 9102. A high density SNP-based genetic linkage map was constructed through double-digest restriction-site-associated DNA sequencing (ddRADseq) technique based on Yuanza 9102 derived recombinant inbred lines (RILs) population. The map contained 2,187 SNP markers distributed on 20 linkage groups (LGs) spanning 1566.10 cM, and showed good synteny with AA genome from A. duranensis and BB genome from A. ipaensis. Phenotypic frequencies of BW resistance among RIL population showed two-peak distribution in four environments. Four QTLs explaining 5.49 to 23.22% phenotypic variance were identified to be all located on chromosome B02. The major QTL, qBWB02.1 (12.17–23.33% phenotypic variation explained), was detected in three environments showing consistent and stable expression. Furthermore, there was positive additive effect among these major and minor QTLs. The major QTL region was mapped to a region covering 2.3 Mb of the pseudomolecule B02 of A. ipaensis which resides in 21 nucleotide-binding site -leucine-rich repeat (NBS-LRR) encoding genes. The result of the major stable QTL (qBWB02.1) not only offers good foundation for discovery of BW resistant gene but also provide opportunity for deployment of the QTL in marker-assisted breeding in peanut
Metabolomics combined with transcriptomics analyses of mechanism regulating testa pigmentation in peanut
Peanut testa (seed coat) contains large amounts of flavonoids that significantly influence seed color, taste, and nutritional qualities. There are various colors of peanut testa, however, their precise flavonoid components and regulatory mechanism of pigmentation remain unclear. In this study, a total of 133 flavonoids were identified and absolutely quantified in the seed coat of four peanut cultivars with different testa color using a widely targeted metabolomic approach. Black peanut skin had more types and substantial higher levels of cyanidin-based anthocyanins, which possibly contribute to its testa coloration. Procyanidins and flavan-3-ols were the major co-pigmented flavonoids in the red, spot and black peanuts, while flavanols were the most abundant constitutes in white cultivar. Although the concentrations as well as composition characteristics varied, the content ratios of procyanidins to flavan-3-ols were similar in all samples except for white peanut. Furthermore, MYB-like transcription factors, anthocyanidin reductases (ANR), and UDP-glycosyltransferases (UGT) were found to be candidate genes involved in testa pigmentation via RNA-seq and weighted gene co-expression network analysis. It is proposed that UGTs and ANR compete for the substrate cyanidin and the prevalence of UGTs activities over ANR one will determine the color pattern of peanut testa. Our results provide a comprehensive report examining the absolute abundance of flavonoid profiles in peanut seed coat, and the finding are expected to be useful for further understanding of regulation mechanisms of seed coat pigmentation in peanut and other crops
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