Biology subjects

Jander, G.

Publications and source records attributed to Jander, G..

7 recordsLinked to original sources

bioRxiv2018

Silencing cathepsin L expression reduces Myzus persicae protein content and the nutritional value as prey for Coccinella septempunctata

Gut-expressed aphid genes, which may be more easily inhibited by RNA interference (RNAi) constructs, are attractive targets for pest control efforts involving transgenic plants. Here we show that expression of cathepsin L, a cysteine protease that functions in aphid guts, can be reduced by expression of an RNAi construct in transgenic tobacco. The effectiveness of this approach is demonstrated by up to 80% adult mortality, reduced fecundity, and delayed nymph production of Myzus persicae (green peach aphids) when cathepsin L expression was reduced by plant-mediated RNAi. Consistent with the function of cathepsin L as a gut protease, M. persicae fed on the RNAi plants had a lower protein content in their bodies and excreted more protein in their honeydew. Larvae of Coccinella septempunctata (seven-spotted ladybugs) grew more slowly on aphids having reduced cathepsin L expression, suggesting that prey insect nutritive value, and not just direct negative effects of the RNAi construct, needs to be considered when producing transgenic plants for RNAi-mediated pest control.\n\nHighlightsO_LISilencing expression of cathepsin L by RNA interference reduces protein content of Myzus persicae (green peach aphid) bodies.\nC_LIO_LIHoneydew of aphids with cathepsin L silenced contains elevated protein.\nC_LIO_LICathepsin L is required for efficient protein uptake from phloem sap.\nC_LIO_LIAphids with cathepsin L expression silenced have increased mortality and fewer offspring.\nC_LIO_LICoccinella septempunctata (seven-spotted ladybugs) grow more slowly on aphids with expression of cathepsin L silenced.\nC_LI\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=173 SRC=\"FIGDIR/small/451211_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (26K):\norg.highwire.dtl.DTLVardef@5ee6d7org.highwire.dtl.DTLVardef@853fe8org.highwire.dtl.DTLVardef@26c2aborg.highwire.dtl.DTLVardef@b67e2b_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2018

Genome sequence of the corn leaf aphid (Rhopalosiphum maidis Fitch)

BackgroundThe corn leaf aphid (Rhopalosiphum maidis Fitch) is the most economically damaging aphid pest on maize (Zea mays), one of the worlds most important grain crops. In addition to causing direct damage due to the removal of photoassimilates, R. maidis transmits several destructive maize viruses, including Maize yellow dwarf virus, Barley yellow dwarf virus, Sugarcane mosaic virus, and Cucumber mosaic virus.\n\nFindingsA 326-Mb genome assembly of BTI-1, a parthenogenetically reproducing R. maidis clone, was generated with a combination of PacBio (208-fold coverage) and Illumina sequencing (80-fold coverage), which contains a total of 689 contigs with an N50 size of 9.0 Mb. The contigs were further clustered into four scaffolds using the Phase Genomics Hi-C interaction maps, consistent with the commonly observed 2n = 8 karyotype of R. maidis. Most of the assembled contigs (473 spanning 321 Mb) were successfully orientated in the four scaffolds. The R. maidis genome assembly captured the full length of 95.8% of the core eukaryotic genes, suggesting that it is highly complete. Repetitive sequences accounted for 21.2% of the assembly, and a total of 17,647 protein-coding genes were predicted in the R. maidis genome with integrated evidence from ab initio and homology-based gene predictions and transcriptome sequences generated with both PacBio and Illumina. An analysis of likely horizontally transferred genes identified two from bacteria, seven from fungi, two from protozoa, and nine from algae.\n\nConclusionsA high-quality R. maidis genome was assembled at the chromosome level. This genome sequence will enable further research related to ecological interactions, virus transmission, pesticide resistance, and other aspects of R. maidis biology. It also serves as a valuable resource for comparative investigation of other aphid species.

genomics↗

bioRxiv2018

Metabolome-scale genome-wide association studies reveal chemical diversity and genetic control of maize specialized metabolites

One Sentence SummaryHPLC-MS metabolite profiling of maize seedlings, in combination with genome-wide association studies, identifies numerous quantitative trait loci that influence the accumulation of foliar metabolites.\n\nAbstractCultivated maize (Zea mays) retains much of the genetic and metabolic diversity of its wild ancestors. Non-targeted HPLC-MS metabolomics using a diverse panel of 264 maize inbred lines identified a bimodal distribution in the prevalence of foliar metabolites. Although 15% of the detected mass features were present in >90% of the inbred lines, the majority were found in <50% of the samples. Whereas leaf bases and tips were differentiated primarily by flavonoid abundance, maize varieties (stiff-stalk, non-stiff-stalk, tropical, sweet corn, and popcorn) were differentiated predominantly by benzoxazinoid metabolites. Genome-wide association studies (GWAS), performed for 3,991 mass features from the leaf tips and leaf bases, showed that 90% have multiple significantly associated loci scattered across the genome. Several quantitative trait locus hotspots in the maize genome regulate the abundance of multiple, often metabolically related mass features. The utility of maize metabolite GWAS was demonstrated by confirming known benzoxazinoid biosynthesis genes, as well as by mapping isomeric variation in the accumulation of phenylpropanoid hydroxycitric acid esters to a single linkage block in a citrate synthase-like gene. Similar to gene expression databases, this metabolomic GWAS dataset constitutes an important public resource for linking maize metabolites with biosynthetic and regulatory genes.

genetics↗

bioRxiv2018

Ethylene signaling regulates natural variation in the abundance of antifungal acetylated diferuloylsucroses and Fusarium graminearum resistance in maize seedling roots

O_LIThe production and regulation of defensive specialized metabolites plays a central role in pathogen resistance in maize (Zea mays) and other plants. Therefore, identification of genes involved in plant specialized metabolism can contribute to improved disease resistance.\nC_LIO_LIWe used comparative metabolomics to identify previously unknown antifungal metabolites in maize seedling roots, and investigated the genetic and physiological mechanisms underlying their natural variation using quantitative trait locus (QTL) mapping and comparative transcriptomics approaches.\nC_LIO_LITwo maize metabolites, smilaside A (3,6-diferuloyl-3',6'-diacetylsucrose) and smiglaside C (3,6-diferuloyl-2',3',6'-triacetylsucrose), that may contribute to maize resistance against Fusarium graminearum and other fungal pathogens were identified. Elevated expression of an ethylene receptor gene, ETHYLENE INSENSITIVE 2 (ZmEIN2), co-segregated with decreased smilaside A/smiglaside C ratio. Pharmacological and genetic manipulation of ethylene availability and sensitivity in vivo indicated that, whereas ethylene was required for the production of both metabolites, the smilaside A/smiglaside C ratio was negatively regulated by ethylene sensitivity. This ratio, rather than the absolute abundance of these two metabolites, was important for maize seedling root defense against F. graminearum.\nC_LIO_LIEthylene signaling regulates the relative abundance of the two F. graminearum-resistance-related metabolites and affects resistance against F. graminearum in maize seedling roots.\nC_LI

plant biology↗

bioRxiv2018

Fusarium graminearum-Induced Shoot Elongation and Root Reduction in Maize Seedlings Correlate with Later Seedling Blight Severity

Fusarium graminearum seedling blight is a common disease of maize (Zea mays). Development of genetic resistance to seedling blight in maize germplasm requires efficient and accurate quantitative assessment of disease severity. Through artificial inoculation experiments under controlled growth conditions, we determined that host genotype, pathogen genotype, and infection dose influence the extent to which F. graminearum induces shoot elongation and inhibits root growth in maize seedlings. A comparison of fifteen maize inbred lines showed independent variation of these two fungus-induced effects on seedling growth. In a broader survey with nine commercial maize hybrids and three field-collected fungal isolates, there was significant correlation between these seedling growth responses, as well as with later seedling blight severity. Analysis of variance suggested that this variation and the observed correlative relationships were primarily driven by differing pathogenicity of the three fungal isolates. Together, our results indicate that F. graminearum-induced shoot elongation and root reduction in maize seedlings have distinct underlying physiological mechanisms, and that early observations of seedling growth responses can serve as a proxy for investigating natural variation in host resistance and pathogen aggressiveness at later growth stages.

plant biology↗

bioRxiv2017

Spodoptera exigua caterpillar feeding induces rapid defense responses in maize leaves

Insects such as beet armyworm caterpillars (Spodoptera exigua) cause extensive damage to maize (Zea mays) by consuming foliar tissue. Maize plants respond to such insect attack by triggering defense mechanisms that involve large changes in gene expression and the biosynthesis of specialized metabolites and defense signaling molecules. To investigate dynamic maize responses to herbivore feeding, leaves of maize inbred line B73 were infested with S. exigua caterpillars for 1 to 24 hours, followed by comprehensive transcriptomic and metabolomic characterization. Our results show that the most significant gene expression responses of maize to S. exigua feeding occur at early time points, within 4 to 6 hours after caterpillar infestation. However, both gene expression and metabolite profiles continued changing during the entire 24-hour experiment while photosynthesis genes were gradually decreased. The primary and specilaze metabolism shift maught be temporal and dynamic processes in the infested leaf tissue. We analyzed the effects of mutating genes in two major defense-related pathways, benzoxazinoids (Bx1 and Bx2) and jasmonic acid (Lox8), using Dissociation (Ds) transposon insertions in maize inbred line W22. Together, these results show that maize leaves shift to implementation of chemical defenses within one hour after the initiation of caterpillar attack. Thus, the induced biosynthesis of specialized metabolites can have major effects in maize-caterpillar interactions.\n\nHIGHLIGHTA comprehensive transcriptic and metabolomic profiling time course of maize foliar responses to caterpillar feeding identifies genes for the synthesis of benzoxazinoids and phytohormones.

plant biology↗

bioRxiv2016

A global co-expression network approach for connecting genes to specialized metabolic pathways in plants

Plants produce a tremendous diversity of specialized metabolites (SMs) to interact with and manage their environment. A major challenge hindering efforts to tap this seemingly boundless source of pharmacopeia is the identification of SM pathways and their constituent genes. Given the well-established observation that the genes comprising a SM pathway are co-regulated in response to specific environmental conditions, we hypothesized that genes from a given SM pathway would form tight associations (modules) with each other in gene co-expression networks, facilitating their identification. To evaluate this hypothesis, we used 10 global co-expression datasets--each a meta-analysis of hundreds to thousands of expression experiments--across eight plant model organisms to identify hundreds of modules of co-expressed genes for each species. In support of our hypothesis, 15.3-52.6% of modules contained two or more known SM biosynthetic genes (e.g., cytochrome P450s, terpene synthases, and chalcone synthases), and module genes were enriched in SM functions (e.g., glucoside and flavonoid biosynthesis). Moreover, modules recovered many experimentally validated SM pathways in these plants, including all six known to form biosynthetic gene clusters (BGCs). In contrast, genes predicted based on physical proximity on a chromosome to form plant BGCs were no more co-expressed than the null distribution for neighboring genes. These results not only suggest that most predicted plant BGCs do not represent genuine SM pathways but also argue that BGCs are unlikely to be a hallmark of plant specialized metabolism. We submit that global gene co-expression is a rich, but largely untapped, data source for discovering the genetic basis and architecture of plant natural products, which can be applied even without knowledge of the genome sequence.

plant biology↗