Biology subjects

Crespi, M.

Publications and source records attributed to Crespi, M..

23 records · Page 2Linked to original sources

bioRxiv2020

An Arabidopsis long noncoding RNA modulates the transcriptome through interactions with a network of splicing factors

Alternative splicing (AS) is a major source of transcriptome and proteome diversity in higher organisms. Long noncoding RNAs (lncRNAs) have emerged as regulators of AS through a range of molecular mechanisms. In Arabidopsis thaliana, the AS regulators NSRa and b, which affect auxin-driven lateral root formation, can interact with the ALTERNATIVE SPLICING COMPETITOR (ASCO) lncRNA. Here, we analyzed the effect of the knockdown and overexpression of ASCO at genome-wide level and found a high number of deregulated and differentially spliced genes, related to flagellin responses and biotic stress. In agreement, roots from ASCO-knocked down plants are more sensitive to flagellin. Surprisingly, only a minor subset of genes overlapped with the AS defects of the nsra/b double mutant. Using biotin-labelled oligonucleotides for RNA-mediated ribonucleoprotein purification, we found that ASCO binds to the highly conserved core spliceosome component PRP8a. ASCO deregulation impairs the recognition of specific flagellin-related transcripts by PRP8a and SmD1b, another spliceosome component, suggesting that ASCO function regulates AS through the interaction with multiple splicing factors. Hence, lncRNAs may interact in a dynamic network with many splicing factors to modulate transcriptome reprogramming in eukaryotes.

molecular biology↗

bioRxiv2019

Genome sequence of the cluster root forming white lupin

White lupin (Lupinus albus L.) is a legume that produces seeds recognized for their high protein content and good nutritional value (lowest glycemic index of all grains, high dietary fiber content, and zero gluten or starch)1-5. White lupin can form nitrogen-fixing nodules but has lost the ability to form mycorrhizal symbiosis with fungi6. Nevertheless, its root system is well adapted to poor soils: it produces cluster roots, constituted of dozens of determinate lateral roots that improve soil exploration and phosphate remobilization7. As phosphate is a limited resource that comes from rock reserves8, the production of cluster roots is a trait of interest to improve fertilizers efficiency. Using long reads sequencing technologies, we provide a high-quality genome sequence of a modern variety of white lupin (2n=50, 451 Mb), as well as de novo assemblies of a landrace and a wild relative. We describe how domestication impacted soil exploration capacity through the early establishment of lateral and cluster roots. We identify the APETALA2 transcription factor LaPUCHI-1, homolog of the Arabidopsis morphogenesis coordinator9, as a potential regulator of this trait. Our high-quality genome and companion genomic and transcriptomic resources enable the development of modern breeding strategies to increase and stabilize yield and to develop new varieties with reduced allergenic properties (caused by conglutins10), which would favor the deployment of this promising culture.

genomics↗

bioRxiv2019

Two ecotype-related long non-coding RNAs in the environmental control of root growth

BackgroundRoot architecture varies widely between species and even between ecotypes of the same species despite the strong conservation of the protein-coding portion of their genomes. In contrast, non-coding RNAs evolved rapidly between ecotypes and may control their differential responses to the environment as several long non-coding RNAs (lncRNAs) can quantitatively regulate gene expression.\n\nResultsRoots from Columbia (Col) and Landsberg erecta (Ler) ecotypes respond differently to phosphate starvation. We compared complete transcriptomes (mRNAs, lncRNAs and small RNAs) of root tips from these two ecotypes during early phosphate starvation. We identified thousands of new lncRNAs categorized as intergenic or antisense RNAs that were largely conserved at DNA level in these ecotypes. In contrast to coding genes, many lncRNAs were specifically transcribed in one ecotype and/or differentially expressed between ecotypes independently of the phosphate condition. These ecotype-related lncRNAs were characterized by analyzing their sequence variability among plants and their link with siRNAs. Our analysis identified 675 lncRNAs differentially expressed between the two ecotypes including specific antisense RNAs targeting key regulators of root growth responses. Mis-regulation of several intergenic lncRNAs showed that at least two ecotype-related lncRNAs regulate primary root growth in Col.\n\nConclusionsThe in depth exploration of the non-coding transcriptome of two ecotypes identified thousands of new lncRNAs showing specific expression in root apexes. De-regulation of two ecotype-related lncRNAs revealed a new pathway involved in the regulation of primary root growth. The non-coding genome may reveal novel mechanisms involved in ecotype adaptation of roots to different soil environments.

plant biology↗

bioRxiv2019

Role of MPK4 in pathogen-associated molecular pattern-triggered alternative splicing in Arabidopsis

Alternative splicing (AS) of pre-mRNAs in plants is an important mechanism of gene regulation in environmental stress tolerance but plant signals involved are essentially unknown. Pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) is mediated by mitogen-activated protein kinases and the majority of PTI defense genes are regulated by MPK3, MPK4 and MPK6. These responses have been mainly analyzed at the transcriptional level, however many splicing factors are direct targets of MAPKs. Here, we studied alternative splicing induced by the PAMP flagellin in Arabidopsis. We identified 506 PAMP-induced differentially alternatively spliced (DAS) genes. Although many DAS genes are targets of nonsense-mediated degradation (NMD), only 19% are potential NMD targets. Importantly, of the 506 PAMP-induced DAS genes, only 89 overlap with the set of 1849 PAMP-induced differentially expressed genes (DEG), indicating that transcriptome analysis does not identify most DASevents. Global DAS analysis of mpk3, mpk4, and mpk6 mutants revealed that MPK4 is a key regulator of PAMP-induced differential splicing, regulating AS of a number of splicing factors and immunity-related protein kinases, such as the calcium-dependent protein kinase CPK28, the cysteine-rich receptor like kinases CRK13 and CRK29 or the FLS2 co-receptor SERK4/BKK1. These data suggest that MAP kinase regulation of splicing factors is a key mechanism in PAMP-induced AS regulation of PTI.\n\nSignificance statementAlternative pre-mRNA splicing (AS) affects plant responses to environmental stresses. So far, however, the regulation of AS is little understood. Here, we studied AS induced by the pathogen-associated molecular pattern (PAMP) flagellin in Arabidopsis. We identified 506 differentially alternatively spliced (DAS) genes, 89 of which overlap with the 1849 DEG, indicating that the majority of DAS events go undetected by common transcriptome analysis. PAMP-triggered immunity is mediated by mitogen-activated protein kinases. Global DAS analysis of MAPK mutants revealed that MPK4 is a key regulator of AS by affecting splicing factors and a number of important protein kinases involved in immunity. Since PAMP-triggered phosphorylation of several splicing factors is directly mediated by MAPKs, we discovered a key mechanism of AS regulation.

plant biology↗

bioRxiv2018

Assessing the response of small RNA populations to allopolyploidy using resynthesized Brassica napus allotetraploids

Allopolyploidy, combining interspecific hybridization with whole genome duplication, has had significant impact on plant evolution. Its evolutionary success is related to the rapid and profound genome reorganizations that allow neo-allopolyploids to form and adapt. Nevertheless, how neo-allopolyploid genomes adapt to regulate their expression remains poorly understood. The hypothesis of a major role for small non-coding RNAs (sRNAs) in mediating the transcriptional response of neo-allopolyploid genomes has progressively emerged. Generally, 21-nt sRNAs mediate post-transcriptional gene silencing (PTGS) by mRNA cleavage whereas 24-nt sRNAs repress transcription (transcriptional gene silencing, TGS) through epigenetic modifications. Here, we characterize the global response of sRNAs to allopolyploidy in Brassica, using three independently resynthesized B. napus allotetraploids surveyed at two different generations in comparison with their diploid progenitors. Our results suggest an immediate but transient response of specific sRNA populations to allopolyploidy. These sRNA populations mainly target non-coding components of the genome but also target the transcriptional regulation of genes involved in response to stresses and in metabolism; this suggests a broad role in adapting to allopolyploidy. We finally identify the early accumulation of both 21- and 24-nt sRNAs involved in regulating the same targets, supporting a PTGS-to-TGS shift at the first stages of the neo-allopolyploid formation. We propose that reorganization of sRNA production is an early response to allopolyploidy in order to control the transcriptional reactivation of various non-coding elements and stress-related genes, thus ensuring genome stability during the first steps of neo-allopolyploid formation.

evolutionary biology↗