Biology subjects

Mueller, L. A.

Publications and source records attributed to Mueller, L. A..

26 records · Page 2Linked to original sources

bioRxiv2020

Comprehensive genotyping of Brazilian Cassava (Manihot esculenta Crantz) Germplasm Bank: insights into diversification and domestication

Cassava (Manihot esculenta Crantz) is a major staple root crop of the tropics, originating from the Amazonas region. In this study, 3,354 cassava landraces and modern breeding lines from the Embrapa Cassava Germplasm Bank (CGB) were characterized. All individuals were subjected to genotyping-by-sequencing (GBS), identifying 27,045 Single Nucleotide Polymorphisms (SNPs). Identity-by-state and population structure analyses revealed a unique set of 1,536 individuals and 10 distinct genetic groups with heterogeneous linkage disequilibrium (LD). On this basis, 1,300 to 4,700 SNP markers were selected for large quantitative trait loci (QTL) detection. Identified genetic groups were further characterized for population genetics parameters including minor allele frequency (MAF), observed heterozygosity (Ho), effective population size estimate [Formula] and polymorphism information content (PIC). Selection footprints and introgressions of M. glaziovii were detected. Spatial population structure analysis revealed five ancestral populations related to distinct Brazilian ecoregions. Estimation of historical relationships among identified populations suggest earliest population split from Amazonas to Atlantic forest and Caatinga eco-regions and active gene flows. This study provides a thorough genetic characterization of ex situ germplasm resources from cassava center of origin, South America, with results shedding light on Brazilian cassava characteristics and its biogeographical landscape. These Findings support and facilitate the use of genetic resources in modern breeding programs including implementation of association mapping and genomic selection strategies. Key messageBrazilian cassava diversity was characterized through population genetics and clustering approaches, highlighting contrasted genetic groups, and spatial genetic differentiation.

plant biology↗

bioRxiv2020

Genetic architecture and gene mapping of cyanide in cassava (Manihot esculenta Crantz.)

Cassava is a root crop originating from South America and a major staple crop in the Tropics, including marginal environments. In this study, we focused on South American and African cassava germplasm and investigated the genetic architecture of Hydrogen Cyanide (HCN), a major component of tuber quality. HCN is a plant defense component against herbivory but also toxic for human consumption. We genotyped 3,354 landraces and modern breeding lines originating from 26 Brazilian states and 1,389 individuals were phenotypically characterized across multi-year trials for HCN. All plant material was subjected to high density genotyping using Genotyping-by-sequencing (GBS). We performed genome wide association mapping (GWAS) to characterize the genetic architecture and gene mapping of HCN. Field experiment revealed strong broad and narrow-sense trait heritability (0.82 and 0.41 respectively). Two major loci were identified, encoding for an ATPase and a MATE protein and contributing up to 7% and 30% of the cyanide concentration in roots, respectively. We developed diagnostic markers for breeding applications, validated trait architecture consistency in African germplasm and investigated further evidence for domestication of sweet and bitter cassava. Fine genomic loci characterization indicate; (i) a major role played by vacuolar transporter in regulating HCN content, (ii) co-domestication of sweet and bitter cassava major alleles to be geographical zone dependant, and (ii) major loci allele for high cyanide cassava in Manihot esculenta Crantz seems to originate from its ancestor, M. esculenta ssp. flabellifolia. Taken together these findings expand insights on cyanide in cassava and its glycosylated derivatives in plants. One-sentence summaryIdentification of an intracellular transporter gene and its allelic variation allow to point out cultivars with up to 30 percent decrease in cassava root cyanide content, toxic for human consumption.

genetics↗

bioRxiv2020

A Solanum lycopersicoides reference genome facilitates biological discovery in tomato

Wild relatives of tomato are a valuable source of natural variation in tomato breeding, as many can be hybridized to the cultivated species (Solanum lycopersicum). Several, including Solanum lycopersicoides, have been crossed to S. lycopersicum for the development of ordered introgression lines (ILs). Despite the utility of these wild relatives and their associated ILs, limited finished genomes have been produced to aid genetic and genomic studies. We have generated a chromosome-scale genome assembly for Solanum lycopersicoides LA2951 using PacBio sequencing, Illumina, and Hi-C. We identified 37,938 genes based on Illumina and Isoseq and compared gene function to the available cultivated tomato genome resources, in addition to mapping the boundaries of the S. lycopersicoides introgressions in a set of cv. VF36 x LA2951 introgression lines (IL). The genome sequence and IL map will support the development of S. lycopersicoides as a model for studying fruit nutrient/quality, pathogen resistance, and environmental stress tolerance traits that we have identified in the IL population and are known to exist in S. lycopersicoides.

genomics↗

bioRxiv2019

Citrusgreening.org: An open access and integrated systems biology portal for the Huanglongbing (HLB) disease complex

We have created an open access web portal with pathosystem-wide resources and bioinformatics tools for the host citrus, the vector Asian citrus psyllid (ACP) and multiple pathogens including Ca. Liberibacter asiaticus. To the best of our knowledge, this is the first example of a database to use the pathosystem as a holistic framework to understand an insect transmitted plant disease. This endeavor integrates and enables the analysis of data sets generated by the community to study the citrus greening disease complex. Users can submit relevant data sets to enable sharing and allow the community to better analyze their data within an integrated system. The portal contains a variety of tools for omics data. Metabolic pathway databases, CitrusCyc and DiaphorinaCyc provide organism specific pathways that can be used to mine metabolomics, transcriptomics and proteomics results to identify pathways and regulatory mechanism involved in disease response. Psyllid Expression Network (PEN) contains expression profiles of ACP genes from multiple life stages, tissues, conditions and hosts. Citrus Expression Network (CEN) contains public expression data from multiple tissues and conditions for various citrus hosts. All tools like Apollo/JBrowse, Biocyc, Blast, CEN and PEN connect to a central database containing gene models for citrus, ACP and multiple Liberibacter pathogens. The portal also includes electrical penetration graph (EPG) recordings of ACP feeding on citrus, information about citrus rootstock trials and metabolomics data in addition to traditional omics data types with a goal of combining and mining all information related to a pathosystem. The portal includes user-friendly manual curation tools to allow the research community to continuously improve this knowledge base as more experimental research is published. Bulk downloads are available for all genome and annotation datasets from the FTP site (ftp://ftp.citrusgreening.org). The portal can be accessed at https://citrusgreening.org/.

bioinformatics↗

bioRxiv2019

An improved de novo assembly and annotation of the tomato reference genome using single-molecule sequencing, Hi-C proximity ligation and optical maps

The original Heinz 1706 reference genome was produced by a large team of scientists from across the globe from a variety of input sources that included 454 sequences in addition to full-length BACs, BAC and fosmid ends sequenced with Sanger technology. We present here the latest tomato reference genome (SL4.0) assembled de novo from PacBio long reads and scaffolded using Hi-C contact maps. The assembly was validated using Bionano optical maps and 10X linked-read sequences. This assembly is highly contiguous with fewer gaps compared to previous genome builds and almost all scaffolds have been anchored and oriented to the 12 tomato chromosomes. We have found more repeats compared to the previous versions and one of the largest repeat classes identified are the LTR retrotransposons. We also describe updates to the reference genome and annotation since the last publication. The corresponding ITAG4.0 annotation has 4,794 novel genes along with 29,281 genes preserved from ITAG2.4. Most of the updated genes have extensions in the 5 and 3 UTRs resulting in doubling of annotated UTRs per gene. The genome and annotation can be accessed using SGN through BLAST database, Pathway database (SolCyc), Apollo, JBrowse genome browser and FTP available at https://solgenomics.net.

genomics↗

bioRxiv2019

Rapid and independent evolution of ancestral and novel defenses in a genus of toxic plants (Erysimum, Brassicaceae)

Phytochemical diversity is thought to result from coevolutionary cycles as specialization in herbivores imposes diversifying selection on plant chemical defenses. Plants in the speciose genus Erysimum (Brassicaceae) produce both ancestral glucosinolates and evolutionarily novel cardenolides as defenses. Here we test macroevolutionary hypotheses on co-expression, co-regulation, and diversification of these potentially redundant defenses across this genus. We sequenced and assembled the genome of E. cheiranthoides and foliar transcriptomes of 47 additional Erysimum species to construct a highly resolved phylogeny, revealing that cardenolide diversity increased rapidly rather than gradually over evolutionary time. Concentrations, inducibility, and diversity of the two defenses varied independently among species, with no evidence for trade-offs. Closely related species shared similar cardenolide traits, but not glucosinolate traits, likely as a result of specific selective pressures acting on distinct molecular diversification mechanisms. Ancestral and novel chemical defenses in Erysimum thus appear to provide complementary rather than redundant functions.

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↗

bioRxiv2017

Biocuration as an undergraduate training experience: Improving the annotation of the insect vector of Citrus greening disease

The Asian citrus psyllid (Diaphorina citri Kuwayama) is the insect vector of the bacterium Candidatus Liberibacter asiaticus (CLas), the pathogen associated with citrus Huanglongbing (HLB, citrus greening). HLB threatens citrus production worldwide. Suppression or reduction of the insect vector using chemical insecticides has been the primary method to inhibit the spread of citrus greening disease. Accurate structural and functional annotation of the Asian citrus psyllid genome, as well as a clear understanding of the interactions between the insect and CLas, are required for development of new molecular-based HLB control methods. A draft assembly of the D. citri genome has been generated and annotated with automated pipelines. However, knowledge transfer from well-curated reference genomes such as that of Drosophila melanogaster to newly sequenced ones is challenging due to the complexity and diversity of insect genomes. To identify and improve gene models as potential targets for pest control, we manually curated several gene families with a focus on genes that have key functional roles in D. citri biology and CLas interactions. This community effort produced 530 manually curated gene models across developmental, physiological, RNAi regulatory, and immunity-related pathways. As previously shown in the pea aphid, RNAi machinery genes putatively involved in the microRNA pathway have been specifically duplicated. A comprehensive transcriptome enabled us to identify a number of gene families that are either missing or misassembled in the draft genome. In order to develop biocuration as a training experience, we included undergraduate and graduate students from multiple institutions, as well as experienced annotators from the insect genomics research community. The resulting gene set (OGS v1.0) combines both automatically predicted and manually curated gene models. All data are available on https://citrusgreening.org/.

genomics↗