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A novel Gram-stain-negative, aerobic strain, designated Y22T, was isolated from peanut field soil in Laoshan Mountain in China. Cells of strain Y22T were rod-shaped and motile by a single flagellum. The strain was found to be oxidase- and catalase-positive. 16S rRNA gene sequence based on phylogenetic analysis indicated that strain Y22T belonged to the genus Pseudomonas, and showed the highest 16S rRNA gene sequence similarity of 99.0% to Pseudomonas pelagia JCM 15562T, followed by Pseudomonas salina JCM 19469T (98.4%), Pseudomonas sabulinigri JCM 14963T (97.9%), Pseudomonas bauzanensis CGMCC 1.9095T (97.6%) and Pseudomonas litoralis KCTC23093T (97.5%). The phylogenetic analysis based on multilocus sequence analyses with concatenated 16S rRNA, gyrB, rpoD and rpoB genes indicated that strain Y22T belonged to Pseudomonas pertucinogena lineage. The average nucleotide identity scores between strain Y22T and closely related species were 74.6–82.8%, and the Genome-to-Genome Distance Calculator scores were 16.4–44.9%. The predominant cellular fatty acids of strain Y22T were C18:1ω7c (29.6%), C17:0 cyclo (17.5%) and summed feature 3 (C16:1ω7c and/or C16:1ω6c) (17.4%). The genomic DNA G+C content was 57.9 mol%. On the basis of phenotypic characteristics, phylogenetic analyses and in silico DNA–DNA relatedness, a novel species, Pseudomonas laoshanensis sp. nov. is proposed. The type strain is Y22T (= JCM 32580T = KCTC 62385T = CGMCC 1.16552T).

Peanut or groundnut (Arachis hypogaea L.), a legume of South American origin, has high seed oil content (45–56%) and is a staple crop in semiarid tropical and subtropical regions, partially because of drought tolerance conferred by its geocarpic reproductive strategy. We present a draft genome of the peanut A-genome progenitor, Arachis duranensis, and 50,324 protein-coding gene models. Patterns of gene duplication suggest the peanut lineage has been affected by at least three polyploidizations since the origin of eudicots. Resequencing of synthetic Arachis tetraploids reveals extensive gene conversion in only three seed-to-seed generations since their formation by human hands, indicating that this process begins virtually immediately following polyploid formation. Expansion of some specific gene families suggests roles in the unusual subterranean fructification of Arachis. For example, the S1Fa-like transcription factor family has 126 Arachis members, in contrast to no more than five members in other examined plant species, and is more highly expressed in roots and etiolated seedlings than green leaves. The A. duranensis genome provides a major source of candidate genes for fructification, oil biosynthesis, and allergens, expanding knowledge of understudied areas of plant biology and human health impacts of plants, informing peanut genetic improvement and aiding deeper sequencing of Arachis diversity.

Haematococcus pluvialis is a green alga known to accumulate the keto-carotenoid astaxanthin under stress conditions. In H. pluvialis, carotenoids are derived from isopentenyl diphosphate (IPP), which is synthesized via the non-mevalonate methyl-d-erythritol 4-phosphate (MEP) pathway. The present study revealed that several treatments caused changes in pigment profiles and the expression levels of genes encoding MEP pathway enzymes. Additionally, photosynthesis fluorescence was monitored. Generally, under stress conditions, there was an increase in astaxanthin, along with a decrease in total chlorophyll and photo capacity. Six IPP biosynthetic genes were cloned from H. pluvialis. Expression analysis revealed that these transcripts were upregulated under stress culture conditions. However, the extent of MEP pathway gene expression varied with the stress conditions. 4-Diphosphocytidyl-2-C-methyl-d-erythritol (CDP-ME) synthase (CMS) and CDP-ME kinase (CMK) exhibited significantly higher transcriptional expression under nitrogen starvation treatments. While 1-deoxy-d-xylulose 5-phosphate (DXP) synthase (DXS), CMS, CMK 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate (HMBPP) synthase (HDS), and HMBPP reductoisomerase (HDR) showed significant upregulation on the second day under nitrogen starvation and high light (HL-N). The enhanced expression of these genes was also observed on the third day under high light. The high expression of MEP pathway genes was correlated with the accumulation of astaxanthin under HL-N stress. This is the first report of the isolation of IPP biosynthetic genes and their differential expression in H. pluvialis under stress conditions. The present study revealed the influence of stress conditions on the expression of MEP pathway genes and changes in pigment profiles.

The cultivated peanut (Arachis hypogaea L.) is important oil crop and cold stress seriously influences its development and yields. Tolerant varieties produced using transgenic techniques will effectively increase peanut plantation area and enhance yields. However, little is known about the network of gene expression regulation related to cold stress in peanut. Therefore, we screened genes regulated by cold stress in peanut. In total, 1478 up-regulated and 1510 down-regulated probe sets were successfully identified in leaves of peanut subjected to cold stress using the microarray technique. Data analysis indicated that the main biological processes involved in cold stress response included signal transduction, transcript regulations and accumulation of soluble metabolites. Regulation of cell division, translation, protein modification, transport and DNA/RNA-related processes were also involved in peanut cold acclimation. Our study also revealed that protein kinases, transcription factors, heat shock proteins, resistance proteins, stilbene synthase, and so on, may play important functions in cold stress regulation of peanut. The function of some probe sets in cold stress regulation had not been clarified (e.g. proteins functioning in glycerol ether metabolic process, microtubule-based movement or nutrient reservoir activity). Some genes we identified lack functional annotation and their roles in response to cold are yet to be elucidated. These results showed an overview of the transcription map of peanut under cold stress, which may yield some useful insights into cold-mediated signal transduction pathways in peanut and offer some candidate genes as potential markers of tolerance to cold stress.

The MYB superfamily constitutes one of the most abundant groups of transcription factors and plays central roles in developmental processes and defense responses in plants. In the work described in this article, 30 unique peanut MYB genes that contained full-length cDNA sequences were isolated. The 30 genes were grouped into three categories: one R1R2R3-MYB, nine R2R3-MYBs and 20 MYB-related members. The sequence composition of the R2 and R3 repeats was conserved among the nine peanut R2R3-MYB proteins. Phylogenetic comparison of the members of this superfamily between peanut and Arabidopsis revealed that the putative functions of some peanut MYB proteins were clustered into the Arabidopsis functional groups. Expression analysis during abiotic stress identified a group of MYB genes that responded to at least one stress treatment. This is the first comprehensive study of the MYB gene family in peanut.

Phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) catalyses phosphoenolpyruvate (PEP) to yield oxaloacetate, which is involved in protein biosynthesis. Pyruvate kinase (PK; EC 2.7.1.40) catalyzes PEP to yield pyruvate, which is involved in fatty acid synthesis. In this study, five PEPC genes (AhPEPC1, AhPEPC2, AhPEPC3, AhPEPC4, and AhPEPC5) from peanut have been cloned. Using a quantitative real-time RT-PCR approach, the expression pattern of each gene was monitored during the seed development of four peanut varieties (E11, Hebeigaoyou, Naihan 1, and Huayu 26). It was found that these five genes shared similar expression behaviors over the developmental stages of E11 with high expression levels at 30 and 40 d after pegging (DAP); whereas these five genes showed irregular expression patterns during the seed development of Hebeigaoyou. In Naihan 1 and Huayu 26, the expression levels of the five genes remained relatively high in the first stage. The PEPC activity was monitored during the seed development of four peanut varieties and seed oil content was also characterized during whole period of seed development. The PEPC activity followed the oil accumulation pattern during the early stages of development but they showed a significantly negative correlation thereafter. These results suggested that PEPC may play an important role in lipid accumulation during the seed development of four peanut varieties tested.

Several ethylene-responsive element binding factor (ERF) family proteins have been demonstrated to play important roles in transcriptional regulation of a variety of biological processes, including responses to environmental conditions such as drought, salt, and cold. To date, there have been no reports on this family in peanut. In this study, 40 ESTs in a peanut cDNA library, whose amino acid sequences contained AP2/ ERF domain, have been identified. Of these, full-length sequences of six genes were cloned. Sequence analysis indicated that all six proteins contained only one AP2/ ERF domain and should belong to the ERF family. The six genes were designated Arachis hypogaea ERF 1–6 (AhERF1–6). The expression patterns of AhERF1–6 were analyzed under cold, salt and drought stress. The results indicated that the expression of AhERF4 and AhERF6 were rapidly and substantially enhanced under abiotic stress. The expression of AhERF1 and AhEERF5 were slightly enhanced under certain stress conditions. Some genes were down-regulated when under stress, such as AhEERF3 in leaves under salt stress and AhERF2 in leaves under drought stress. Interestingly, the expression of AhERF3 and AhERF5 exhibited contrary expression patterns in peanut leaves and roots upon PEG treatment. These results suggested that different ERF proteins may have different functions in peanut abiotic stress acclimation.

Purified and enriched brain microglia from neonatal chickens were infected with live Marek's disease virus (MDV)-both the very virulent (vv) YL040920 strain and the attenuated vaccine strain CVI988/Rispens in vitro. Although YL040920-infected microglia showed lower viral DNA loads compared with those infected with CVI988/Rispens at the same infectious dose (400 plaque-forming units for each), no significant differences in IFN-γ and IL-12p35 transcription were detected between the two MDV strains. Chicken microglia infected with live or fixed YL040920 expressed dramatically higher levels of IL-12p40, IL-8, and macrophage inflammatory protein-1β (MIP-1β) transcripts compared with those infected with CVI988/Rispens. On the other hand, CVI988/Rispens induced significantly higher levels of IFN-β transcription than YL040920, especially the live virus. Inducible nitric oxide (NO) synthase (iNOS) transcription and NO production correlated with levels of both YL040920 and CVI988/Rispens live strain infection. Moreover, fixed MDVs induced higher levels of iNOS/NO than live viruses, especially with CVI988/Rispens. This study demonstrates that chicken microglial cells can become infected with live YL040920 and CVI988/Rispens and that microglia represent cellular sources of IL-12p40, IL-12p35, IFN-γ, IFN-β, IL-8, MIP-1β, iNOS mRNA, and NO expression after MDV infection in vitro. Transcription levels of IL-12p35 and IFN-γ were associated with MDV DNA replication, whereas transcription levels of IL-12p40, IFN-β, IL-8, and MIP-1β were associated with both MDV DNA replication and expression of viral specific genes. The transcription of iNOS was responsible for expression of viral specific genes, whereas it was suppressed by viral DNA replication during infection. Although YL040920, compared with CVI988/Rispens, induced similar levels of the typical Th1-type cytokine IFN-γ in microglia, vvMDV induced significant increases in other cytokines [IL-12 (p40 and 12p35), IL-8, and MIP-1β]. More detailed investigation, as well as in vivo testing of the effects of vvMDV infection on Th1 responses, iNOS expression, and NO production in the brain of chickens should be undertaken.

Fatty acid desaturases can introduce double bonds into the hydrocarbon chains of fatty acids to produce unsaturated fatty acids. In the present study, 29 full-length desaturase genes were identified from soybean genome by a thorough annotation exercise. A comprehensive analysis was performed to characterize phylogeny, chromosomal locations, structures, conserved motifs, and expression patterns of those genes. The soybean genes were phylogenetically clustered into nine subfamilies with the Arabidopsis counterparts, FAB2, FAD2, FAD3, FAD5, FAD6, FAD7, FAD8, SLD1, and DES1. Twenty-nine desaturase genes were found to be distributed on at least 15 of the 20 soybean chromosomes. The gene structures and motif compositions were considerably conserved among the subfamilies. The majority of desaturase genes showed specific temporal and spatial expression patterns across different tissues and developmental stages based on microarray data analyses. The study may provide new insights into the origin and evolution of fatty acid biosynthesis pathways in higher plants. Additionally, the characterization of desaturases from soybean will lead to the identification of additional genes for genetic modification of plants to produce nutritionally important fatty acids.

Phosphoenolpyruvate carboxylase (PEPC) is widely distributed in plants and bacteria, and catalyzes the carboxylation of phosphoenolpyruvate to form oxaloacetate and inorganic phosphate. To investigate the molecular mechanisms of the regulation and control of peanut oil, with the degenerated primers and RACE-PCR approach, five PEPC genes were cloned from peanut, and designated as AhPEPC1, AhPEPC2, AhPEPC3, AhPEPC4, and AhPEPC5, respectively. The structure and phylogenetic analysis of PEPC protein indicated that AhPEPC1-4 genes encoded a typical plant-type PEPC-enzyme, and AhPEPC5 a bacterial-type. By real-time quantitative RT-PCR approach the expression pattern of each gene was detected in various tissues of normal and high oil-content peanut varieties. It was found that there was a lower expression level of AhPEPCs genes except for the AhPEPC2 in high-oil peanut than normal-oil peanut line. The results provide some fundamental information for the further investigation of plant PEPC proteins and their role in regulation of oil-content in peanut seeds.

Delta(12) fatty acid desaturase gene has been targeted as a logical candidate controlling the high oleate trait in peanut seeds. By RT-PCR method, the full-length cDNAs of Delta(12) fatty acid desaturase gene were isolated from peanut (Arachis hypogaea L.) genotypes with normal and high ratio of oleic to linoleic acid, which were designated AhFAD2B and AhFAD2B', respectively. Sequence alignment of their coding regions revealed that an extra A was inserted at the position +442 bp of AhFAD2B' sequence of high oleic acid genotypes, which resulted in the shift of open reading frame and a truncated protein AhFAD2B', with the loss of one histidine box involved in metal ion complex required for the reduction of oxygen. Analysis of transcript level showed that the expression of Delta(12) fatty acid desaturase gene in high oleic acid genotype was slightly lower than that in normal genotype. The enzyme activity experiment of yeast (Saccharomyces cerevisiae) cell transformed with AhFAD2B or AhFAD2B' proved that only AhFAD2B gene product showed significant Delta(12) fatty acid desaturase activity, but AhFAD2B' gene product did not. These results suggested that the change of AhFAD2B' gene sequence resulted in lower activity or deactivation of Delta(12) fatty acid desaturase in high oleic acid genotype.

Background MicroRNAs (miRNAs) are noncoding RNAs of approximately 21 nt that regulate gene expression in plants post-transcriptionally by endonucleolytic cleavage or translational inhibition. miRNAs play essential roles in numerous developmental and physiological processes and many of them are conserved across species. Extensive studies of miRNAs have been done in a few model plants; however, less is known about the diversity of these regulatory RNAs in peanut (Arachis hypogaea L.), one of the most important oilseed crops cultivated worldwide. Results A library of small RNA from peanut was constructed for deep sequencing. In addition to 126 known miRNAs from 33 families, 25 novel peanut miRNAs were identified. The miRNA* sequences of four novel miRNAs were discovered, providing additional evidence for the existence of miRNAs. Twenty of the novel miRNAs were considered to be species-specific because no homolog has been found for other plant species. qRT-PCR was used to analyze the expression of seven miRNAs in different tissues and in seed at different developmental stages and some showed tissue- and/or growth stage-specific expression. Furthermore, potential targets of these putative miRNAs were predicted on the basis of the sequence homology search. Conclusions We have identified large numbers of miRNAs and their related target genes through deep sequencing of a small RNA library. This study of the identification and characterization of miRNAs in peanut can initiate further study on peanut miRNA regulation mechanisms, and help toward a greater understanding of the important roles of miRNAs in peanut.

Quantitative real-time reverse transcription PCR (qRT-PCR), a sensitive technique for quantifying gene expression, depends on the stability of the reference gene(s) used for data normalization. Only a few studies on the reference genes have been done with peanut to date. In the present study, 14 potential reference genes in peanut were evaluated for their expression stability using the geNorm and NormFinder statistical algorithms. Expression stability was assessed by qRT-PCR across 32 biological samples, including various tissue types, seed developmental stages, salt and cold treatments. The results showed that the best-ranked references genes differed across the samples. UKN1, UKN2, TUA5 and ACT11 were the most stable across all the tested samples. A combination of ACT11, TUA5, UKN2, PEPKR1 and TIP41 would be appropriate as a reference panel for normalizing gene expression data across the various tissues tested, whereas the combination of TUA5 and UKN1 was the most suitable for seed developmental stages. TUA5 and EF1b exhibited the most stable expression under cold treatment. For salt-treated leaves, TUA5 and UKN2 were the most stably expressed and HDC and UKN1 for salt-treated roots. The relative gene expression level of peanut Cys(2)/His(2)-type zinc finger protein gene AhZFP1 was analyzed in order to validate the reference genes selected for this study. These results provide guidelines for the selection of reference genes under different experimental conditions and also a foundation for more accurate and widespread use of qRT-PCR in peanut gene analysis.

Kosteletzkya virginica is a halophyte species which could be used for production of industrial raw material such as biodiesel and for developing ecologically sound saline agriculture as well as for tideland soil improving. Using Rapid Amplification of cDNA Ends (RACE) method, a 1610 bp cDNA of stearoyl-ACP desaturase (SAD) gene containing a 1188 bp complete open reading fragment (ORF) was firstly isolated from seeds of K. virginica. Sequence analysis revealed that the nucleotide sequence of K. virginica SAD had a high level of homology to SAD from Gossypium hirsutum, but had relative low identity to SAD from other pants. However, K. virginica SAD had a high level of amino acid sequence homology to SAD from other plants. Characteristics of the deduced protein were predicted and analyzed using bioinformatic methods. Expression analysis via real-time PCR indicated that expression levels of the SAD gene were markedly distinct in different K. virginica tissues and different development stage seeds. The results of the expression analysis in this study, combined with existing research, suggest that SAD may be involved in the regulation of plant seed growth and development. These results serve as a foundation for further studies of the mechanisms regulating SAD gene expression and could eventually lead to the development of higher quality K. virginica varieties.

β-ketoacyl-ACP synthetase II (KAS II) which catalyzes the elongation of 16:0-ACP to 18:0-ACP，determines the ratio of palmitic acid (16:0) to stearic acid (18:0). Using Rapid Amplification of cDNA Ends (RACE) and a peanut cDNA library we had previously constructed, we isolated a 1867bp cDNA of the KAS II gene containing a 1212bp complete open reading fragment (ORF). Sequence analysis revealed that peanut KAS II had a high level of nucleotide and amino acid sequence homology to KAS II from other plants. Phylogenetic analysis showed that KAS II from plants, bacteria and virus were grouped into different clades respectively suggesting the independent evolution of KAS II from different sources. Characteristics of the deduced protein were predicted and analyzed using bioinformatic methods. The protein was predicted as stable and hydrophobic with molecular weight of 43181.4 and theoretical PI of 5.69. Expression analysis by real-time PCR indicated that expression levels of KAS II gene were markedly distinct in different peanut tissues and varieties. The expression analysis in this study combined with existing researches suggested KAS II may be involved in the regulation of plant growth and development.

Acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) catalyzes the synthesis of malonyl-CoA, the first intermediate in fatty acid synthesis. Genes for multi-functional acetyl-CoA carboxylase and two subunits of multi-subunit acetyl-CoA carboxylase, biotin carboxylase and β-Carboxyltransferase, have been cloned from peanut. The ORF of the three proteins are 6783bp, 1623bp, 1479 bp in length, encoding 2260, 540, 492 amino acids, respectively. The predicted amino acid sequences of the multi-functional AhACCase and AhBC from peanut shared high sequence identity, 90.9% and 88%, to the corresponding Glycine max proteins, respectively, while the amino acid sequence of AhβCT gene showed 71.6% identity with that from Nothofagus gunnii. Phylogenetic analysis showed that all of these three genes from peanut were grouped into the big branch of proteins from higher plant. Moreover, observation of the tree revealed that multi-functional ACCase genes may arise by independent gene duplication events in green algae and higher plants branches, and the biotin carboxylase and β-Carboxyltransferase genes from cyanobacteria may be the origin of genes from higher plants, mosses and eukaryotic algae.

The plant C2H2-type zinc finger proteins play important roles in plant tolerance to abiotic stresses. In this study, we isolated the full-length cDNA of a C2H2-type zinc finger protein gene AhZFP1 from peanut (Arachis hypogaea L.). AhZFP1 encodes a 24.75kDa protein with two C2H2-type zinc finger domains. Phylogenetic analysis showed that the AhZFP1 was close to Arabidopsis zinc finger protein AZF2. The semi-quantitative RT-PCR assay revealed that the expression of AhZFP1 was induced by salt stress in peanut roots, stems and leaves. AhZFP1 was the first C2H2-type zinc finger protein gene reported in peanut.

β-ketoacyl-acyl carrier protein synthase (KAS) plays a pivotal role in de novo fatty acid biosynthesis, joining short carbon units to construct fatty acyl chains by a three-step Claisen condensation reaction in plants and bacteria. A putative KASâ… cDNAs was isolated from peanut by searching a peanut seedling full-length cDNA library. The AhKASâ… contains four strictly conserved residues Cys221–His361–Lys392–His397 in the active site, which is an important characteristic of KAS Is in plants and bacteria. The AhKAS â… gene containing 1 912 bp cDNA sequence with a 1 413 bp ORF, encodes 470 amino acids. The predicted amino acid sequences translated from the AhKASâ… gene shared 90.2% sequence identity to the corresponding protein in Glycine max . The cDNA was cloned into plasmid pET-28a and expressed in Escherichia coli BL21. Quantitative real-time PCR analysis suggested AhKAS â… was expressed with higher levels in leaf and seed than those in other tissues. In addition, AhKAS â… RNA was found in high abundance at 45 and 65 DAP (days after pegging) during seed development. This work may serve as a foundation for further studies on the mechanisms regulating the expression of KAS â… gene and provide candidate genes for modifying oil quality via transgenic plants.

Fatty acid biosynthesis is catalysed in most bacteria and plants by a group of highly conserved proteins known as the Type II fatty acid synthase (FAS) system. In this study, genes for β-ketoacyl-ACP reductase (KR), β-hydroxyacyl-ACP dehydrase (HD), and enoyl-ACP reductase (ENR) of Type II FAS have been cloned from peanut ( Arachis hypogaea L.). The results showed that the ORF of the three genes were 972 bp, 651 bp and 1170 bp in length, encoding 323, 216 and 389 amino acids, respectively. The predicted amino acid sequences of AhKR, AhHD, AhENR shared high sequence identity of 86.3%, 81.2% and 87.2% to the corresponding ones in Glycine max, respectively. Further investigation of quantitative real-time RT-PCR analysis suggested that AhKR, AhHD and AhENR were expressed with higher levels in leaf and seed than those in root and stem tissues. Moreover, AhKR and AhENR genes reached a maximum expression level at 25 DAP (days after pegging) and showed a downward trend thereafter. In contrast, AhHD gene expressed in an irregular course during seed development. Overall, the information generated by this study will facilitate the manipulation of the quality of oils produced in seeds of oil crops.

The primary role of aquaporins is to control water transport in plants, which might function in plant response against salt stress. In this research, we obtained the full-length cDNA of an aquaporin gene AhAQ1 by RT-PCR approach from salt-stressed peanut leaves. AhAQ1 encodes a protein consisting of 287 amino acids with the calculated molecular mass of 30.57 KD and the isoelectric point of 9.04. Sequence analysis indicated that AhAQ1 contained six transmembrane domains and two NPA-boxes and phylogenetic analysis showed that the AhAQ1 clusters were the same with the PIP1 family. The expression pattern of AhAQ1 in peanut tissues under high-salt treatment was examined by semi-quantitative RT-PCR, The results showed that the accumulation of AhAQ1 transcripts was induced by salt stress . The combination of these results illustrate that AhAQ1 may play a role in peanut in response to salt stress.

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Lysophosphatidyl acyltransferase (LPAAT) is a pivotal enzyme controlling the metabolic flow of lysophosphatidic acid into different phosphatidic acids in diverse tissues. The functions of LPAAT genes have been intensively studied in Arabidopsis, but not in peanut (Arachis hypogaea L.). In this study, conventional RT-PCR or RACE (rapid amplification of cDNA ends)-PCR were used to clone four AhLPAAT genes from peanut. Quantitative real-time RT-PCR analysis indicated that AhLPAAT2 transcript was more abundant in seeds, whereas the transcript abundances of other three genes were higher in flowers than in other tissues examined. During seed development, levels of AhLPAAT6 transcripts decreased, whereas levels of other three transcripts remained relatively high at the initial stages of seed development but dramatically decreased in abundance during later stages. Expression analysis of four genes under conditions of cold, salt, drought and ABA stresses indicated that AhLPAAT transcripts were differentially regulated during abiotic stresses. Transcripts of the four genes increased substantially in leaves exposed to drought stress. Levels of AhLPAAT2 transcript were distinctly enhanced after exposure to cold, salt and drought stresses, whereas AhLPAAT4 was obviously up-regulated after salt, drought and ABA treatments. The expressions of AhLPAAT6 increased in all materials after stress treatments except for salt-stressed leaves, whereas transcript levels of AhLPAAT5 only increased in cold- and drought-stressed leaves and ABA-treated roots. These insights into peanut LPAATs may facilitate modification of oil deposition and improvement of abiotic stress resistance in this important crop.

Pre-harvest aflatoxin contamination caused by Aspergillus favus is a major concern in peanut. However, little is known about the resistance mechanism, so the incorporation of resistance into cultivars with commercially-acceptable genetic background has been slowed. To identify resistance-associated genes potentially underlying the resistance mechanism, we compared transcriptome profiles in resistant and susceptible peanut genotypes under three different treatments: well watered, drought stress and both A. flavus and drought stress using a customised NimbleGen microarray representing 36 158 unigenes. Results showed that the profile of differentially expressed genes (DEGs) displayed a similar pattern of distribution among the functional classes between resistant and susceptible peanuts in response to drought stress. Under A. flavus infection with drought stress, a total of 490 unigenes involved in 26 pathways were differentially expressed in the resistant genotype YJ1 uniquely responding to A. flavus infection, in which 96 DEGs were related to eight pathways: oxidation reduction, proteolysis metabolism, coenzyme A biosynthesis, defence response, signalling, oligopeptide transport, transmembrane transport and carbohydrate biosynthesis/metabolism. Pathway analysis based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) database showed that eight networks were significantly associated with resistance to A. flavus infection in resistant genotype YJ1 compared with susceptible Yueyou7. To validate microarray analysis, 15 genes were randomly selected for real-time RT–PCR analysis. The results provided in this study may enhance our understanding of the pre-harvest peanut–A. flavus interaction and facilitate to develop aflatoxin resistant peanut lines in future breeding programs.