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Background and aims: Serotonin (5-hydroxtryptamine, 5-HT) is an important factor in gut function, playing key roles in intestinal peristalsis and secretion, and in sensory signalling in the brain-gut axis. Removal from its sites of action is mediated by a specific protein called the serotonin reuptake transporter (SERT or 5-HTT). Polymorphisms in the promoter region of the SERT gene have effects on transcriptional activity, resulting in altered 5-HT reuptake efficiency. It has been speculated that such functional polymorphisms may underlie disturbance in gut function in individuals suffering with disorders such as irritable bowel syndrome (IBS). The aim of this study was to assess the potential association between SERT polymorphisms and the diarrhoea predominant IBS (dIBS) phenotype. Subjects: A total of 194 North American Caucasian female dIBS patients and 448 female Caucasian controls were subjected to genotyping. Methods: Leucocyte DNA of all subjects was analysed by polymerase chain reaction based technologies for nine SERT polymorphisms, including the insertion/deletion polymorphism in the promoter (SERT-P) and the variable tandem repeat in intron 2. Statistical analysis was performed to assess association of any SERT polymorphism allele with the dIBS phenotype. Results:A strong genotypic association was observed between the SERT-P deletion/deletion genotype and the dIBS phenotype (p = 3.07 ×10-5; n = 194). None of the other polymorphisms analysed was significantly associated with the presence of disease. Conclusions:Significant association was observed between dIBS and the SERT-P deletion/deletion genotype, suggesting that the serotonin transporter is a potential candidate gene for dIBS in women. [ABSTRACT FROM AUTHOR]

Background: Maize (Zea mays L.) is a major cereal crop, with the United States accounting for over 40% of the worldwide production. Corn leaf aphid [CLA; Rhopalosiphum maidis (Fitch)] is an economically important pest of maize and several other monocot crops. In addition to feeding damage, CLA acts as a vector for viruses that cause devastating diseases in maize. We have shown previously that the maize inbred line Mp708, which was developed by classical plant breeding, provides heightened resistance to CLA. However, the transcriptomic variation conferring CLA resistance to Mp708 has not been investigated., Results: In this study, we contrasted the defense responses of the resistant Mp708 genotype to those of the susceptible Tx601 genotype at the transcriptomic (mRNA-seq) and volatile blend levels. Our results suggest that there was a greater transcriptomic remodeling in Mp708 plants in response to CLA infestation compared to the Tx601 plants. These transcriptomic signatures indicated an activation of hormonal pathways, and regulation of sesquiterpenes and terpenoid synthases in a constitutive and inducible manner. Transcriptomic analysis also revealed that the resistant Mp708 genotype possessed distinct regulation of ethylene and jasmonic acid pathways before and after aphid infestation. Finally, our results also highlight the significance of constitutive production of volatile organic compounds (VOCs) in Mp708 and Tx601 plants that may contribute to maize direct and/or indirect defense responses., Conclusions: This study provided further insights to understand the role of defense signaling networks in Mp708's resistance to CLA.

12-Oxo-phytodienoic acid (OPDA), an intermediate in the jasmonic acid (JA) biosynthesis pathway, regulates diverse signaling functions in plants, including enhanced resistance to insect pests. We previously demonstrated that OPDA promoted enhanced callose accumulation and heightened resistance to corn leaf aphid (CLA; Rhopalosiphum maidis ), a phloem sap-sucking insect pest of maize ( Zea mays ). In this study, we used the electrical penetration graph (EPG) technique to monitor and quantify the different CLA feeding patterns on the maize JA-deficient 12-oxo-phytodienoic acid reductase ( opr7opr8 ) plants. CLA feeding behavior was unaffected on B73, opr7opr8 control plants (- OPDA), and opr7opr8 plants that were pretreated with OPDA (+ OPDA). However, exogenous application of OPDA on opr7opr8 plants prolonged aphid salivation, a hallmark of aphids' ability to suppress the plant defense responses. Collectively, our results indicate that CLA utilizes its salivary secretions to suppress or unplug the OPDA-mediated sieve element occlusions in maize., (© 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

The corn leaf aphid (CLA; Rhopalosiphum maidis ) is a phloem sap-sucking insect that attacks many cereal crops, including maize ( Zea mays ). We previously showed that the maize inbred line Mp708, which was developed by classical plant breeding, provides enhanced resistance to CLA. Here, using electrophysiological monitoring of aphid feeding behavior, we demonstrate that Mp708 provides phloem-mediated resistance to CLA. Furthermore, feeding by CLA on Mp708 plants enhanced callose deposition, a potential defense mechanism utilized by plants to limit aphid feeding and subsequent colonization. In maize, benzoxazinoids (BX) or BX-derived metabolites contribute to enhanced callose deposition by providing heightened resistance to CLA. However, BX and BX-derived metabolites were not significantly altered in CLA-infested Mp708 plants, indicating BX-independent defense against CLA. Evidence presented here suggests that the constitutively higher levels of 12-oxo-phytodienoic acid (OPDA) in Mp708 plants contributed to enhanced callose accumulation and heightened CLA resistance. OPDA enhanced the expression of ethylene biosynthesis and receptor genes, and the synergistic interactions of OPDA and CLA feeding significantly induced the expression of the transcripts encoding Maize insect resistance1-Cysteine Protease, a key defensive protein against insect pests, in Mp708 plants. Furthermore, exogenous application of OPDA on maize jasmonic acid-deficient plants caused enhanced callose accumulation and heightened resistance to CLA, suggesting that the OPDA-mediated resistance to CLA is independent of the jasmonic acid pathway. We further demonstrate that the signaling function of OPDA, rather than a direct toxic effect, contributes to enhanced CLA resistance in Mp708., (© 2019 American Society of Plant Biologists. All Rights Reserved.)

Metacaspases are distant relatives of animal caspases found in plants, protozoa and fungi. Some recent studies have demonstrated that metacaspases are involved in regulating the developmental and environmentally induced programmed cell death in plants. In this study, we identified metacaspase gene family in potato ( Solanum tuberosum L.) and analyzed their expression pattern in various developmental tissues and stress responses of plants. There were eight metacaspase genes identified in the Peptidase (Cysteine protease) C14 family and based upon sequence alignment and phylogenetic analysis, a systematic nomenclature of potato metacaspases (SotubMCs) has been proposed. Three of the eight candidate genes showing homology with Arabidopsis thaliana type I metacaspase, AtMC1 were given name SotubMC1, SotubMC2 and SotubMC3 as per the degree of relatedness. Similarly, the next three being homologous to A. thaliana type I metacaspase, AtMC3 were named SotubMC4, SotubMC5, and SotubMC6. The remaining two were named SotubMC7 and SotubMC8, showing significant similarity with type II metacaspases of A. thaliana, AtMC4 and AtMC9, respectively. Evolutionary divergence analysis of SotubMCs from its orthologs in seven other members of Solanaceae family as well as with A. thaliana , Vitis vinifera and Oryza sativa was also carried out. The d N /d S ratios of the orthologous pairs suggested the SotubMCs were under purifying (negative) selection in course of plant evolution. Splicing patterns of potato metacaspases were also analyzed. Amongst all SotubMCs, SotubMC2, SotubMC4, SotubMC6 and SotubMC7 genes appeared to produce multiple alternative spliced variants of different lengths. Furthermore using protein modeling tools, we have predicted the protein structure of identified metacaspases. The cis-regulatory elements analysis was also performed exhibiting the presence of development, stress and hormones related cis-elements in the promoter regions of the SotubMCs. This indicates that potato metacaspases might be playing important roles in the development, stress and hormone responsive pathways. Moreover, relative expression analysis of identified genes was carried out using qRT-PCR in various developmental tissues that also include stolons and tubers. The eight metacaspases showed differential expression in different tissues. Some of the tissues such as leaf undergoing senescence among different leaf developmental stages (immature, mature and senescent) displayed higher relative expression of some of the metacaspases, implying their involvement in leaf senescence. The expression pattern of SotubMCs under various abiotic, biotic and hormonal stresses was also analysed. The results showed that many members of the potato metacaspase gene family displayed differential expression patterns under various stress conditions. Taken together, the study could provide crucial resources for further investigations to understand the functional roles of the identified metacaspases in potato.

Chewing herbivores, such as caterpillars and beetles, while feeding on the host plant, cause extensive tissue damage and release a wide array of cues to alter plant defenses. Consequently, the cues can have both beneficial and detrimental impacts on the chewing herbivores. Herbivore-associated molecular patterns (HAMPs) are molecules produced by herbivorous insects that aid them to elicit plant defenses leading to impairment of insect growth, while effectors suppress plant defenses and contribute to increased susceptibility to subsequent feeding by chewing herbivores. Besides secretions that originate from glands (e.g., saliva) and fore- and midgut regions (e.g., oral secretions) of chewing herbivores, recent studies have shown that insect frass and herbivore-associated endosymbionts also play a critical role in modulating plant defenses. In this review, we provide an update on a growing body of literature that discusses the chewing insect HAMPs and effectors and the mechanisms by which they modulate host defenses. Novel "omic" approaches and availability of new tools will help researchers to move forward this discipline by identifying and characterizing novel insect HAMPs and effectors and how these herbivore-associated cues are perceived by host plant receptors.

The vasculature of plants act as a channel for transport of signal(s) that facilitate long-distance intraplant communication. In maize, Maize insect resistance1-Cysteine Protease (Mir1-CP), which has homology to papain-like proteases, provides defense to different feeding guilds of insect pests. Furthermore, accumulation of Mir1-CP in the vasculature suggests that Mir1-CP can potentially function as a phloem-mobile protein. In a recent study, we provided evidence that Mir1-CP can curtail the growth of phloem-sap sucking insect, corn leaf aphid (CLA; Rhopalosiphum maidis). Our current study further examined whether aboveground feeding by CLA can induce resistance to subsequent herbivory by belowground feeding western corn rootworm (WCR; Diabrotica virgifera virgifera). Aboveground feeding by CLA systemically induced the accumulation of Mir1-CP in the roots. Furthermore, foliage feeding by CLA provided enhanced resistance to subsequent herbivory by belowground feeding of WCR. Taken together, our previous findings and results presented here indicate that long-distance transport of Mir1-CP is critical for providing enhanced resistance to insect attack in maize.

Signaling networks among multiple phytohormones fine-tune plant defense responses to insect herbivore attack. Previously, it was reported that the synergistic combination of ethylene (ET) and jasmonic acid (JA) was required for accumulation of the maize insect resistance1 (mir1) gene product, a cysteine (Cys) proteinase that is a key defensive protein against chewing insect pests in maize (Zea mays). However, this study suggests that mir1-mediated resistance to corn leaf aphid (CLA; Rhopalosiphum maidis), a phloem sap-sucking insect pest, is independent of JA but regulated by the ET-signaling pathway. Feeding by CLA triggers the rapid accumulation of mir1 transcripts in the resistant maize genotype, Mp708. Furthermore, Mp708 provided elevated levels of antibiosis (limits aphid population)- and antixenosis (deters aphid settling)-mediated resistance to CLA compared with B73 and Tx601 maize susceptible inbred lines. Synthetic diet aphid feeding trial bioassays with recombinant Mir1-Cys Protease demonstrates that Mir1-Cys Protease provides direct toxicity to CLA. Furthermore, foliar feeding by CLA rapidly sends defensive signal(s) to the roots that trigger belowground accumulation of the mir1, signifying a potential role of long-distance signaling in maize defense against the phloem-feeding insects. Collectively, our data indicate that ET-regulated mir1 transcript accumulation, uncoupled from JA, contributed to heightened resistance to CLA in maize. In addition, our results underscore the significance of ET acting as a central node in regulating mir1 expression to different feeding guilds of insect herbivores., (© 2015 American Society of Plant Biologists. All Rights Reserved.)

Asthma is a complex disease and the intricate interplay between genetic and environmental factors underlies the overall phenotype of the disease. Families with at least two siblings with asthma were collected from Europe, Australia and the US. A genome scan using a set of 364 families with a panel of 396 microsatellite markers was conducted. Nonparametric linkage analyses were conducted for asthma and three asthma-related phenotypes: bronchial hyper-reactivity (BHR), strict definition of asthma and atopic asthma. Nine chromosomal regions with LOD scores greater than 1.5 were identified (chromosomes 1q, 2p, 3q, 4p, 4q, 6q, 12q, 20p and 21). Linkage refinement analysis was performed for three BHR loci by genotyping single nucleotide polymorphisms at an average marker density of 1 cM. The LOD scores increased to 3.07 at chromosome 4p and 4.58 at chromosome 2p, while the chromosome 6p locus did not refine. The LOD score at the chromosome 2p locus is highly significant on a genome-wide basis. The refined locus covers a region with a physical size of 12.2 Mb. Taken together, these results provide evidence for a major asthma susceptibility locus on chromosome 2p.