Biology subjects

Blein, T.

Publications and source records attributed to Blein, T..

17 recordsLinked to original sources

bioRxiv2026

Stealth CAR-Tregs evade CD3 antibody therapy and skew immune responses toward regulation

Organ transplantation standard of care relies on lifelong immunosuppression, increasing infection and malignancy risks. An emerging approach using Chimeric Antigen Receptor Regulatory T cells (CAR-Tregs) targeting donor antigens, allows the suppression of alloimmune responses while preserving protective immunity. However, transplant recipients harbor a substantial pool of alloreactive memory T-cells, limiting CAR-Tregs tolerance-promoting effect. To address this challenge, our strategy combines selective depletion of activated T-cells, using non-mitogenic CD3 antibody therapy, with HLA-A2-targeted-CAR-Treg therapy. We established that T-cell receptor alpha chain (TRAC) deletion does not impair CAR-Treg antigen-specific activation, expansion, or their transcriptomic, phenotypic, epigenetic, and functional profiles. TRAC-/-CAR-Tregs exhibit robust protection from CD3 antibody depletion in circulation and peripheral tissues, whereas most TRAC+/+CAR-T cells are eliminated. Importantly, TRAC+/+CAR-T cells that escape CD3 antibody mediated depletion exhibit a transcriptomic signature consistent with T-cell exhaustion. Our findings demonstrate that CD3 antibody therapy provides an in vivo survival advantage to TRAC-/-CAR-Tregs, thereby shifting the immune balance toward regulation. This approach might enhance the translational potential of CAR-Treg therapy by reducing the required cell dose needed for clinical efficacy.

immunology↗

bioRxiv2026

The long non-coding RNA ACHLYS modulates biomolecular condensates to regulate alternative splicing in root development

Alternative splicing (AS) enables eukaryotes to dynamically adjust RNA and protein isoforms encoded in one gene. Long non-coding RNAs (lncRNA) have emerged as novel regulators of AS through multiple modes of action, including interactions with splicing factor (SF) proteins. Here, we used Arabidopsis thaliana lateral root development to dissect the specificity of lncRNAs in AS regulation. Data mining and a transient expression screen allowed us to identify novel lncRNAs interacting in vivo with the well-characterized SFs Nuclear speckle RNA binding protein A (NSRa) and glycine-rich RNA-binding protein 7 (GRP7), that are differentially expressed during lateral root organogenesis. We identified 4 lncRNAs affecting more than 250 AS events in plant cells, whereby most AS events are unique for each lncRNA. Notably, 19% of the AS events linked to two NSRa-recognized lncRNAs are identical and positively correlated. One lncRNA was named ACHLYS and is highly conserved in several Brassicaceae whereas another was the recently characterized FLAIL lncRNA. ACHLYS knockdown (KD-ACHLYS) and overexpressing lines (OE-ACHLYS) modulate AS regulation in plants and affect root architecture. In parallel, we performed NSRa-iCLIP to determine in vivo genome-wide NSRa binding sites. Interestingly, NSRa binding sites are locally enriched in ACHLYS-dependent AS introns and ACHLYS itself. A specific ACHLYS-induced AS event requires NSRa function showing that ACHLYS defines AS targets through NSRa interaction on specific transcripts. In vitro assays indicate that direct interaction of NSRa with ACHLYS promotes NSRa phase separation. Furthermore, overexpression of ACHLYS in NSRa-GFP plants results in increased accumulation of NSRa in Nuclear speckles. Our data revealed that ACHLYS can modulate NSRa condensates in vivo and binds to NSRa for modifying AS patterns, suggesting a new mechanism where lncRNAs can fine tune SFs regulation and the transcriptome output in eukaryotic organogenesis.

molecular biology↗

bioRxiv2025

The subunit 3 of the SUPERKILLER (SKI) complex mediates miR172-directed cleavage of Nodule Number Control 1 (NNC1) to modulate nodulation in Medicago truncatula

Legumes and rhizobia establish a nitrogen-fixing symbiosis that involves the formation of a lateral root organ, the nodule, and the infection process that allows intracellular accommodation of rhizobia within nodule cells. This process involves significant gene expression changes regulated at the transcriptional and post-transcriptional levels. We have previously shown that a transcript encoding the subunit 3 of the Superkiller Complex (SKI), which guides mRNAs to the exosome for 3'-to-5' degradation, is required for nodule formation and bacterial persistence within the nodule, as well as the induction of early nodulation genes (e.g., MtENOD40) during the Medicago truncatula-Sinorhizobium meliloti symbiosis. Here, we reveal through transcript degradome and small RNA sequencing analysis that knockdown of MtSKI3 impairs the miR172-directed endonucleolytic cleavage of the mRNA encoding Nodule Number Control 1 (MtNNC1), an APETALA2 transcription factor that negatively modulates nodulation. Knockdown of MtNNC1 enhances nodule number, bacterial infection, and the induction of MtENOD40 upon inoculation with S. meliloti whereas overexpression of a miR172-resistant form of MtNNC1 significantly reduces nodule formation. This work identifies miR172 cleavage of MtNNC1 and its control by MtSKI3, a component of the 3'-to-5'mRNA degradation pathway, as a new regulatory hub controlling indeterminate nodulation.

plant biology↗

bioRxiv2024

The Arabidopsis RNA-binding protein SGS3 is recruited to the chromatin remodeler CHR11 to promote siRNA production from protein-coding genes

In plants, aberrant RNAs produced by endogenous genes or transgenes are normally degraded by the nuclear and cytosolic RNA quality control (RQC) pathways. Under certain biotic or abiotic stresses, RQC is impaired, and aberrant RNAs are converted into siRNAs that initiate post-transcriptional gene silencing (PTGS) in the cytosol. How aberrant RNAs are selected and brought to the cytoplasm is not known. Here we show that the RNA-binding protein SUPPRESSOR OF GENE SILENCING (SGS)3 shuttles between the cytosol and the nucleus where it associates with the ISWI-like CHROMATIN REMODELER (CHR)11. CHR11 binds to transgenes prone to trigger PTGS. Knocking down CHR11 and its paralog CHR17 strongly reduces transgene PTGS, suggesting that SGS3 recruitment by CHR11/17 facilitates PTGS initiation. CHR11 is also enriched at endogenous protein-coding genes (PCGs) producing nat-siRNAs and va-siRNAs under biotic or abiotic stresses, and this production is reduced in chr11 chr17 double mutants at genome-wide level. Moreover, impairing CHR11 and CHR17 rescues the lethal phenotype caused by the massive production of siRNAs from PCGs in RQC-deficient mutants. We propose that SGS3 recruitment by CHR11/17 allows exporting RNAs to the cytosol to initiate the production of siRNAs. One Sentence SummaryThe plant PTGS component SGS3 is recruited by the chromatin remodeler CHR11 to select nuclear RNAs for export to the cytosol and siRNA production.

cell biology↗

bioRxiv2023

The transcription factor NF-YA10 determines the area explored by Arabidopsis thaliana roots through direct regulation of LAZY and TAC genes

Root developmental plasticity relies on transcriptional reprogramming, which largely depends on the activity of transcription factors (TFs). NF-YA2 and NF-YA10 (Nuclear Factor A2 and A10) are down-regulated by the specific miRNA isoform miR169defg, in contrast to miR169a. Here, we analyzed the role of the Arabidopsis thaliana TF NF-YA10 in the regulation of lateral root development. Plants expressing a version of NF-YA10 resistant to miR169 cleavage showed a perturbation in the lateral root gravitropic response. By extracting novel features of root architecture using the ChronoRoot deep-learning-based phenotyping system, we uncovered a differential emergence angle of lateral roots over time when compared to Col-0. Detailed phenotyping of root growth dynamics revealed that NF-YA10 activity modulates the area explored by Arabidopsis roots. Furthermore, we found that NF-YA10 directly regulates TAC1 and LAZY genes by targeting their promoter regions, genes previously linked to gravitropism. Hence, the TF NF-YA10 is a new element in the control of LR gravitropism and root system architecture.

plant biology↗

bioRxiv2022

Regulatory and evolutionary annotation identifies KAN1, MYB44 and PIF4 as regulators of Arabidopsis lincRNAs expressed in root

Thousands of long intergenic noncoding RNAs (lincRNAs) have been identified in plant genomes. While some lincRNAs have been characterized as important regulators in different biological processes, little is known about the transcriptional regulation for most plant lincRNAs. Through the integration of eight annotation resources, we defined 6,599 high-confidence lincRNA loci in Arabidopsis thaliana. For lincRNAs belonging to different evolutionary age categories, we identified major differences in sequence and chromatin features, as well as in the level of conservation and purifying selection acting during evolution. Spatiotemporal gene expression profiles combined with transcription factor (TF) chromatin immunoprecipitation data were used to construct a TF- lincRNA regulatory network containing 2,659 lincRNAs and 15,686 interactions. We found that properties characterizing lincRNA expression, conservation and regulation differ between plants and animals. Experimental validation confirmed the role of three TFs, KAN1, MYB44, and PIF4, as key regulators controlling root- specific lincRNA expression, demonstrating the predictive power of our network. Furthermore, we identified 58 lincRNAs, regulated by these TFs, showing strong root cell-type specific expression or chromatin accessibility, which are linked with GWAS genetic associations related to root system development and growth. The multi-level genome-wide characterization covering chromatin state information, promoter conservation, and ChIP-based TF binding, for all detectable lincRNAs across 769 expression samples, permits to rapidly define the biological context and relevance of lincRNAs in Arabidopsis regulatory networks. One-line sentenceA multi-level Arabidopsis gene regulatory network identifies novel regulators controlling root-specific lincRNA expression, offering a promising strategy to identify lincRNAs involved in plant biology.

plant biology↗

bioRxiv2022

Synergistic action of the Arabidopsis spliceosome components PRP39a and SmD1 in promoting post-transcriptional transgene silencing

Besides regulating splicing, the conserved spliceosome component SmD1 was shown to promote posttranscriptional silencing of sense transgenes (S-PTGS). Here, we show that the conserved spliceosome component PRP39a also plays a role in S-PTGS. However, PRP39a and SmD1 actions appear distinct in both splicing and S-PTGS. Indeed, RNA-seq analysis of prp39a and smd1 mutants identified different sets of deregulated mRNAs and non-coding RNAs, both at expression level and alternative splicing genome-wide. Moreover, double mutant analyses involving prp39a or smd1 and RNA quality control (RQC) mutants revealed genetic interactions of SmD1 and PRP39a with distinct nuclear RQC machineries, suggesting synergistic rather than redundant roles in the RQC/PTGS interplay. Supporting this hypothesis, a prp39a smd1 double mutant exhibited enhanced suppression of S-PTGS compared with single mutants. Because no major changes in the expression of PTGS or RQC components or in small RNA production were identified in prp39a and smd1 mutants, and because prp39a and smd1 mutations do not alter PTGS triggered by inverted-repeat transgenes directly producing dsRNA (IR-PTGS), PRP39a and SmD1 seem to synergistically promote a step specific to S-PTGS. We propose that, independent of their specific roles in splicing, PRP39a and SmD1 limit 3-to-5 and 5-to-3 degradation of transgene aberrant RNAs, respectively, thus favoring the export of aberrant RNAs to the cytoplasm where their transformation into dsRNA initiates S-PTGS.

plant biology↗

bioRxiv2021

Sequence-unrelated long noncoding RNAs converged to modulate the activity of conserved epigenetic machineries across kingdoms

RNA-DNA hybrid (R-loop)-associated long noncoding RNAs (lncRNAs), including the Arabidopsis lncRNA AUXIN-REGULATED PROMOTER LOOP (APOLO), are emerging as important regulators of three-dimensional chromatin conformation and gene transcriptional activity. Here, we showed that in addition to the PRC1-component LIKE-HETEROCHROMATIN PROTEIN 1 (LHP1), APOLO interacts with the methylcytosine-binding protein VARIANT IN METHYLATION 1 (VIM1), a conserved homolog of the mammalian DNA methylation regulator UBIQUITIN-LIKE CONTAINING PHD AND RING FINGER DOMAINS 1 (UHRF1). The APOLO-VIM1-LHP1 complex directly regulates the transcription of the auxin biosynthesis gene YUCCA2 by dynamically determining DNA methylation and H3K27me3 deposition over its promoter during the plant thermomorphogenic response. Strikingly, we demonstrated that the lncRNA UHRF1 Protein Associated Transcript (UPAT), a direct interactor of UHRF1 in humans, can be recognized by VIM1 and LHP1 in plant cells, despite the lack of sequence homology between UPAT and APOLO. In addition, we showed that increased levels of APOLO or UPAT hamper VIM1 and LHP1 binding to YUCCA2 promoter. Collectively, our results uncover a new mechanism in which a plant lncRNA coordinates Polycomb action and DNA methylation, and reveal that evolutionary unrelated lncRNAs may exert similar functions across kingdoms.

plant biology↗

bioRxiv2020

CD28 costimulatory domain protects against tonic signaling-induced functional impairment in CAR-Tregs

The use of chimeric antigen receptor (CAR)-engineered regulatory T cells (Tregs) has emerged as a promising strategy to promote immune tolerance in transplantation. However, in conventional T cells (Tconvs), CAR expression is often associated with tonic signaling resulting from ligand-independent baseline activation. Tonic signaling may cause CAR-T cell dysfunction, especially when the CAR structure incorporates the CD28 costimulatory domain (CSD) rather than the 4-1BB CSD. Here, we explored the impact of tonic signaling on human CAR-Tregs according to the type of CSD. Compared to CD28-CAR-Tregs, 4-1BB-CAR-Tregs showed enhanced proliferation and greater activation of MAP kinase and mTOR pathways but exhibited decreased lineage stability and reduced abilities to produce IL-10 and be restimulated through the CAR. Although both CAR-Treg populations were suppressive in vivo, cell tracking with bioluminescence imaging found longer persistence for CD28-CAR-Tregs than for 4-1BB-CAR-Tregs. This study demonstrates that CD28-CAR best preserves Treg function and survival in the context of tonic signaling, in contrast with previous findings for Tconvs. SUMMARYLamarthee et al investigated the impact of chimeric antigen receptor (CAR) tonic signaling on CAR-engineered Tregs according to the incorporated costimulatory domain (either CD28 or 4-1BB). CD28 ameliorated Treg stability, long-term survival and function compared to 4-1BB.

immunology↗

bioRxiv2020

ChronoRoot: High-throughput phenotyping by deep segmentation networks reveals novel temporal parameters of plant root system architecture

BackgroundDeep learning methods have outperformed previous techniques in most computer vision tasks, including image-based plant phenotyping. However, massive data collection of root traits and the development of associated artificial intelligence approaches have been hampered by the inaccessibility of the rhizosphere. Here we present ChronoRoot, a system which combines 3D printed open-hardware with deep segmentation networks for high temporal resolution phenotyping of plant roots in agarized medium. ResultsWe developed a novel deep learning based root extraction method which leverages the latest advances in convolutional neural networks for image segmentation, and incorporates temporal consistency into the root system architecture reconstruction process. Automatic extraction of phenotypic parameters from sequences of images allowed a comprehensive characterization of the root system growth dynamics. Furthermore, novel time-associated parameters emerged from the analysis of spectral features derived from temporal signals. ConclusionsAltogether, our work shows that the combination of machine intelligence methods and a 3D-printed device expands the possibilities of root high-throughput phenotyping for genetics and natural variation studies as well as the screening of clock-related mutants, revealing novel root traits.

plant biology↗

bioRxiv2020

Identification and functional prediction of anthocyanin biosynthesis regulatory long non-coding RNAs (lncRNAs) in carrot

Carrot (Daucus carota L.) is one of the most cultivated vegetable in the world and of great importance in the human diet. Its storage organs can accumulate large quantities of anthocyanins, metabolites that confer the purple pigmentation to carrot tissues and whose biosynthesis is well characterized. Long non-coding RNAs (lncRNAs) play critical roles in regulating gene expression of various biological processes in plants. In this study, we used a high throughput stranded RNA-seq to identify and analyze the expression profiles of lncRNAs in phloem and xylem root samples using two genotypes with a strong difference in anthocyanin production. We discovered and annotated 8484 new genes, including 2095 new protein-coding and 6373 non-coding transcripts. Moreover, we identified 639 differentially expressed lncRNAs between the phenotypically contrasted genotypes, including certain only detected in a particular tissue. We then established correlations between lncRNAs and anthocyanin biosynthesis genes in order to identify a molecular framework for the differential expression of the pathway between genotypes. A specific natural antisense transcript (NAT) linked to the DcMYB7 key anthocyanin biosynthetic transcription factor suggested how the regulation of this pathway may have evolved between genotypes.

genomics↗

bioRxiv2020

The lncRNA MARS modulates the epigenetic reprogramming of the marneral cluster in response to ABA

Clustered organization of biosynthetic non-homologous genes is emerging as a characteristic feature of plant genomes. The co-regulation of clustered genes seems to largely depend on epigenetic reprogramming and three-dimensional chromatin conformation. Here we identified the long noncoding RNA (lncRNA) MARneral Silencing (MARS), localized inside the Arabidopsis marneral cluster, which controls the local epigenetic activation of its surrounding region in response to ABA. MARS modulates the POLYCOMB REPRESSIVE COMPLEX 1 (PRC1) component LIKE-HETEROCHROMATIN PROTEIN 1 (LHP1) binding throughout the cluster in a dose-dependent manner, determining H3K27me3 deposition and chromatin condensation. In response to ABA, MARS decoys LHP1 away from the cluster and promotes the formation of a chromatin loop bringing together the MARNERAL SYNTHASE 1 (MRN1) locus and a distal ABA-responsive enhancer. The enrichment of co-regulated lncRNAs in clustered metabolic genes in Arabidopsis suggests that the acquisition of novel noncoding transcriptional units may constitute an additional regulatory layer driving the evolution of biosynthetic pathways.

genetics↗

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

Light dynamically regulates growth rate and cellular organisation of the Arabidopsis root meristem.

1Large-scale methods and robust algorithms are needed for a quantitative analysis of cells status/geometry in situ. It allows the understanding the cellular mechanisms that direct organ growth in response to internal and environmental cues. Using advanced whole-stack imaging in combination with pattern analysis, we have developed a new approach to investigate root zonation under different dark/light conditions. This method is based on the determination of 3 different parameters: cell length, cell volume and cell proliferation on the cell-layer level. This method allowed to build a precise quantitative 3D cell atlas of the Arabidopsis root tip. Using this approach we showed that the meristematic (proliferation) zone length differs between cell layers. Considering only the rapid increase of cortex cell length to determine the meristematic zone overestimates of the proliferation zone for epidermis/cortex and underestimates it for pericycle. The use of cell volume instead of cell length to define the meristematic zone correlates better with cell proliferation zone.

plant biology↗