Biology subjects

Offringa, R.

Publications and source records attributed to Offringa, R..

At least 19 recordsLinked to original sources

bioRxiv2026

A phospholipid-dependent PDK1-AGC kinase cascade regulates pollen tube growth

3-PHOSPHOINOSITIDE-DEPENDENT PROTEIN KINASE1 (PDK1), a conserved master regulator of AGC kinases, is encoded by two redundant genes in Arabidopsis thaliana, PDK1 and PDK2. pdk1 pdk2 mutants exhibit a broad range of defects, including apolar or arrested pollen tube growth, a phenotype also observed in agc1.5 agc1.7 mutants. Pollen-specific expression of constitutively active AGC1.5 in pdk1 pdk2 restores polar pollen tube growth, indicating that PDK1 functions upstream of redundant AGC1.5/AGC1.7 signaling in this process. In contrast, the PDK1 splice variant PDK1S0, lacking the phospholipid-binding PH domain, cannot restore polar pollen tube growth. Our results indicate a key role for the phospholipid PI(4,5)P2 in recruiting PDK1 through its PH domain to establish polar pollen tube growth, as PI(4,5)P2 marks the pollen germination initiation site together with PDK1, it forms a dome at the plasma-membrane of the pollen tube tip beneath which PDK1 remains largely cytosolic and exhibits reciprocal feedback regulation with the PDK1-AGC1.5/1.7 kinases. Defects in endocytosis and actin organization further support that phospholipid-dependent PDK1-AGC signaling maintains pollen tube growth polarity.

plant biology↗

bioRxiv2026

Genotype-phenotype mapping identifies fetal-like CD55+ immunoregulatory cancer cells as mediators of immune escape in colorectal cancer

Immune evasion is a defining feature of advanced colorectal cancer (CRC), yet the cellular mechanisms linking cancer cell states to immune suppression remain poorly understood. To systematically map tumour-immune interactions in advanced CRC, we modelled recurrent human CRC mutations using a multiplex CRISPR-based genetically engineered mouse model platform. The resulting 20 models recapitulate key stages, genetic routes and histopathological features of human CRC, while single-cell transcriptomics reveals extensive disease complexity across models. Profiling of the epithelial tumour compartment identified a population of fetal-like immunoregulatory cancer cells (IRCs) characterized by interferon-{gamma} and MAPK activity. IRCs are marked by expression of the membrane-bound complement regulatory protein CD55. Mechanistically, CD55 protects IRCs from immune surveillance and complement-mediated lysis. Together, these findings reveal a cancer cell-immune interface that promotes immune evasion in advanced CRC.

cancer biology↗

bioRxiv2025

The plant longevity gene AHL15 delays leaf senescence by repressing ORESARA1 and cytokinin degradation

The Arabidopsis thaliana (Arabidopsis) AT-HOOK MOTIF NUCLEAR LOCALIZED 15 (AHL15) gene is associated with various longevity phenotypes and extends the life span of plants when overexpressed. In this study, we show that, in addition to previously described longevity phenotypes, constitutive overexpression of AHL15 in Arabidopsis delays leaf senescence, whereas ahl15 loss-of-function accelerates this process. Dexamethasone-induced nuclear localization of AHL15-GR during dark-triggered senescence results in a stay-green phenotype and represses the expression of several early senescence-associated genes. Among these, the ORESARA1 (ORE1) locus is directly bound by AHL15, suggesting a direct repressive effect of AHL15 on senescence. Furthermore, we demonstrate that AHL15 acts by directly repressing the expression of several CYTOKININ OXIDASE (CKX) genes involved in cytokinin inactivation, resulting in a delayed degradation of cytokinins during dark-induced senescence. Cytokinins are known to delay senescence, and together with the downregulation of ORE1 expression, this explains the repressive effect of AHL15 on senescence. SignificanceHere, we show that in addition to its previously reported effects on aging processes, the AT-HOOK MOTIF NUCLEAR LOCALIZED-family protein AHL15 also represses leaf senescence. Our results demonstrate that AHL15 delays the senescence program in two ways: by directly repressing the senescence master regulator ORESARA1, and by transcriptional repression of CYTOKININ OXIDASE genes, resulting in a delayed breakdown of the senescence-inhibiting hormone cytokinin, which together explain the strong stay-green phenotype of AHL15-overexpressing plants.

plant biology↗

bioRxiv2025

The Lettuce Expression Browser: from lab to LEB

Lettuce (Lactuca sativa L.) is an economically important leafy vegetable within the Asteraceae family, cultivated worldwide across diverse agricultural systems. Recent advances in genomic and transcriptomic resources have positioned lettuce as a promising model system for functional genomics in the Asteraceae. However, currently available gene expression datasets lack comprehensive tissue-specific resolution, primarily focus on a single cultivar and are not visualised in an interpretable manner, limiting their utility for broader genetic and physiological studies. To bridge this gap, we developed the Lettuce Expression Browser (LEB), a publicly available platform providing high-resolution gene expression maps across various organs, tissues and developmental stages in both cultivated and wild lettuce species. The LEB integrates transcriptomic data from finely dissected seedlings, shoot tissues at various developmental stages and seedlings subjected to abiotic stresses (salt and far-red), visualised using the ggPlantmap R package. This platform offers an intuitive interface for exploring gene expression patterns and serves as a valuable resource for those studying lettuce development, stress responses, and evolutionary genomics. The LEB is hosted on the LettuceKnow Web Portal (https://lettuce.bioinformatics.nl) and can be expanded to include additional datasets, enhancing its role as a key tool for lettuce research and crop improvement. Significance statementThe Lettuce Expression Browser (LEB) provides the first high-resolution gene expression atlas for both cultivated and wild lettuce species. This open-access resource enables detailed exploration of gene activity across development stages and stress conditions, advancing functional genomics in the Asteraceae family.

plant biology↗

bioRxiv2025

AT-HOOK-MOTIF NUCLEAR LOCALIZED 15 extends plant longevity by binding at poorly accessible, epigenetic mark-depleted chromatin that surrounds transcribed regions

BackgroundMembers of the AT-HOOK MOTIF NUCLEAR LOCALIZED (AHL) gene family have been shown to play important roles in plant development. In Arabidopsis thaliana, one member of this family, AHL15, induces somatic embryogenesis and extends plant longevity when overexpressed - the latter through strong repression of several ageing-related developmental transitions. However, its direct target genes and the mechanisms by which it regulates their expression have remained elusive to date. ResultsIn this study we identified the genome-wide DNA binding sites of AHL15 and show that AHL15 binds throughout the genome at AT-rich sequences near the transcription start- and end sites in regions depleted of epigenetic marks. We show that induction of AHL15 activity causes strong and rapid changes in transcription, with the majority of the differentially expressed genes being downregulated but without directly affecting chromatin accessibility, resulting in developmental defects. In addition, AHL15 binding to regions near the transcription start and end sites was enhanced at genes that were differentially expressed upon AHL15 induction and was especially strong near the transcription start site of upregulated genes and near the transcription end site of downregulated genes. Finally, we show that AHL15 shares binding sites with the chromatin architectural protein GH1-HMGA2/HON5, which was previously shown to alter transcription by disrupting gene loop formation. ConclusionsTogether, our findings suggest that AHL15 affects the expression of its target genes by regulating the 3D organization rather than by changing the accessibility of chromatin or the deposition of histone modifications.

plant biology↗

bioRxiv2025

GreenLeafVI: A FIJI plugin for high-throughput analysis of leaf chlorophyll content

Chlorophyll breakdown is a central process during plant senescence or stress responses and leaf chlorophyll content is therefore a strong predictor of plant health. Chlorophyll quantification can be done in several ways, most of which are time-consuming or require specialized equipment. A simple alternative to these methods is the use of image-based chlorophyll estimation, which uses the color values in RGB images to calculate colorimetric visual indexes as a measure for the leaf chlorophyll content. Image-based chlorophyll measurement is non-destructive and, apart from a digital camera, requires no specialized equipment. Here, we developed the ImageJ plugin GreenLeafVI that facilitates high-throughput image analysis for measuring leaf chlorophyll content. Our plugin offers the option to white-balance images to decrease variation between images and has an optional background removal step. We show that this method can reliably quantify leaf chlorophyll content in a variety of plant species. In addition, we show that image-based chlorophyll quantification can replicate GWAS results based on traditional chlorophyll extraction methods, showing that this method is highly accurate.

plant biology↗

bioRxiv2024

From aerial drone to QTL: Leveraging next-generation phenotyping to reveal the genetics of color and height in field-grown Lactuca sativa

In recent years, the automation of genotyping has significantly enhanced the efficiency of genome-wide association studies. As a result, phenotyping rather than genotyping is now the rate-limiting step, especially in field experiments. For this reason, there is a strong need to further automate in-field phenotyping. Here we present a GWAS study on 194 field-grown accessions of lettuce (Lactuca sativa). These accessions were non-destructively phenotyped at two time points 15 days apart using an unmanned aerial vehicle. Our high throughput phenotyping approach integrates an RGB camera, a multispectral camera to measure the reflectance at 5 wavelengths (blue, green, red, red edge, near-infrared), and precise height estimation. We used the mean and other descriptives such as median, quantiles, minimum and maximum to quantify different aspects of color and height variation in lettuce from the drone images. Using this approach, we confirm several previously described QTLs, now in populations grown under field conditions, and identify several new QTLs for plant-height and color.

plant biology↗

bioRxiv2023

optiPRM: A targeted immunopeptidomics LC-MS workflow with ultra-high sensitivity for the detection of mutation-derived tumor neoepitopes from limited input material

Personalized cancer immunotherapies such as vaccines and T cell receptor (TCR)-transgenic T cells rely on the presentation of tumor-specific peptides by human leukocyte antigen (HLA) class I molecules to cytotoxic T cells. Such neoepitopes can for example arise from somatic mutations and their identification is crucial for the rational design of new therapeutic interventions. For their detection by liquid chromatography mass spectrometry (LC-MS), we have developed a parameter optimization workflow to tune targeted assays for maximum detection sensitivity on a per peptide basis, termed optiPRM. Optimization of collision energy using optiPRM allows for improved detection of low abundant peptides that are very hard to detect using standard parameters. Applying this to immunopeptidomics, we detected a neoepitope in a patient-derived xenograft (PDX) from as little as 2.5x106 cells input. Application of the workflow on small patient tumor samples allowed for the detection of five mutation-derived neoepitopes in three patients. One neoepitope was confirmed to be recognized by patient T cells. In conclusion, we here present optiPRM, a targeted MS workflow reaching ultra-high sensitivity by per peptide parameter optimization, which allowed for the identification of actionable neoepitopes from sample sizes usually available in the clinic.

immunology↗

bioRxiv2023

Incorporation of TRDV segments into TCR alpha chains

In human tumor models we tried to identify and clone the TCR of tumor-reactive T cells enriched in mixed lymphocyte tumor-cell cultures (MLTC). In a particular MLTC, we identified a predominant TCR beta chain using the Beta Mark Vbeta Kit, but a corresponding alpha chain could not be amplified via RT-PCR using TRAV-specific forward primers. Therefore, we applied 5RACE to obtain the TCR alpha chain sequences. The 5RACE product revealed an alpha chain that encompassed 89bp of the TRDV1 5UTR, followed by the TRDV1 coding sequence joined in frame to TRAJ24. The ORF reaching from the TRDV1 start codon to the TRAC segment was intact, suggesting a functional TCR. To analyze this MLTC population in greater depth we conducted 10X VDJ sequencing. CellRanger identified the beta chain known from the Beta Mark analysis, but no corresponding alpha chain in the filtered results. The corresponding TRDV-containing TCR alpha chain could, however, be detected in the "all_contig_annotations" files. In a separate project, we performed TCR sequencing of tumor-infiltrating lymphocytes (TILs) in a murine tumor model. Also here, a predominant clonotype contained a TCR alpha chain joining Trdv2-2 in frame to Traj49. Transfection of both TCR cDNAs resulted in cell surface localization of TCR and CD3 as validated by FACS. Tumor recognition of the human, TRDV1-containing TCR could be demonstrated by IFNgamma ELISpot whereas the murine TCR did not recognize a tumor-derived cell line. TRDV-containing alpha chains have been reported in the literature for two HLA I-restricted TCRs against HIV peptides (Ueno et al, Eur J Immunol, 2003). To determine whether such TDRV-containing TCRs are unique events or whether Vdelta segments are commonly incorporated into TCR alpha chains, we queried the NCBI Sequence Read Archive (SRA) for 10X VDJ data and analyzed 21 human and 23 murine datasets. We found that especially TRDV1, Trdv1 and to some extent Trdv2-2 are more commonly incorporated into TCR alpha chains than some TRAV genes, making the TRDV segments a relevant contribution to TCR alpha diversity. For apparently solitary beta chains in 10X VDJ datasets, we suggest to scrutinize the "all_contig_annotations" files as these may contain an accompanying, TRDV-containing alpha chain.

immunology↗

bioRxiv2022

The effect of short-term activation of AHL15 on long-term plant developmental change and transcriptome profile

We have previously documented that overexpression of the Arabidopsis nuclear protein AHL15 leads to reprogramming of somatic cells to embryonic cells (Karami et al., 2021) and to suppression of plant ageing (Karami et al., 2020). Here we show that transient (4 hours) activation of overexpressed AHL15-GR in Arabidopsis seedlings has long-term effects on plant development. RNA sequencing analysis detected an extensive reprogramming of the transcriptome 4 hours after AHL15-GR activation, with respectively 540 and 1107 genes showing more than 2-fold up- and down-regulation. AHL15 seemed to act in a transcription leveldependent manner, activating predominantly low expressed genes and repressing mostly highly expressed genes. Rapid decondensation of heterochromatin was observed after AHL15 activation in leaf primordia and axillary meristems, indicating that the global reprogramming of the transcriptome by transient activation of this AT-Hook domain protein might be caused by extensive modulation of the chromatin configuration. We also found that co-activated or co-repressed genes were often physically linked in small chromosomal clusters, which is in line with regulation at the chromatin level.

developmental biology↗

bioRxiv2022

Key role of auxin cellular accumulation in totipotency and pluripotency acquisition

Genome editing and in vitro based-plant propagation require efficient plant regeneration system. Somatic embryogenesis (SE) or de novo shoot regeneration are two major systems that widely used for plant in vitro regeneration. Most SE or shoot regeneration protocols rely on the exogenous application of the synthetic auxin analog 2,4-dichlorophenoxyacetic acid (2,4-D) and naphthylene acetic acid (NAA), whereas the natural auxins indole-3-acetic acid (IAA), 4-chloroindole-3-acetic acid (4-Cl-IAA) or indole-3-butyric acid (IBA) are not or less effective for plant regeneration. Although these synthetic auxins mimics the physiological activity of the main natural auxin IAA in many aspects, there are also clear differences that have been attributed to differences in stability or to different affinities for certain TIR1/AFB-Aux/IAA auxin co-receptor pairs. Here we show that the success of 2,4-D in inducing SE from Arabidopsis is related to ineffectiveness as substrate for auxin efflux, resulting in its intracellular 2,4-D accumulation. Reducing auxin efflux by addition of the auxin transport inhibitor naphthylphthalamic acid (NPA) also allowed natural auxins and other synthetic analogs to induce SE in Arabidopsis with similar efficiencies as 2,4-D. The PIN-FORMED auxin efflux carriers PIN1, PIN2 and the ATP-binding cassette-B auxin transporters ABCB1 and ABCB19 were shown to be partially responsible for the efflux of natural auxins during SE induction. Importantly, all somatic embryos induced in Arabidopsis by IAA in the presence of NPA showed a normal embryo to seedling conversion and subsequent plant development, whereas for the 2,4-D system this was limited to 50-60% of the embryos. We showed that the auxin transport inhibition promotes de novo shoot regeneration capacity from callus induced by 4-Cl-IAA in Brassica napus. In addition, we observed a obvious acceleration in shoot bud emerging from callus induced by 4-Cl-IAA than 2,4-D. Based on our data we conclude, that the efficiency of plant propagation can be significantly improved by applying the natural auxins in the presence of the auxin transport inhibitor NPA.

plant biology↗

bioRxiv2022

Structure-activity relationship of 2,4-D correlates auxin activity with the induction of somatic embryogenesis in Arabidopsis thaliana

2,4-dichlorophenoxyacetic acid (2,4-D) is a synthetic analogue of the plant hormone auxin that is commonly used in many in vitro plant regeneration systems, such as somatic embryogenesis (SE). Its effectiveness in inducing SE, compared to the natural auxin indole-3-acetic acid (IAA), has been attributed to the stress triggered by this compound rather than its auxin activity. However, this hypothesis has never been thoroughly tested. Here we used a library of 40 2,4-D analogues to test the structure-activity relationship with respect to the capacity to induce SE and auxin activity in Arabidopsis thaliana. Four analogues induced SE as effectively as 2,4-D and 13 analogues induced SE but were less effective. Based on root growth inhibition and auxin response reporter expression, the 2,4-D analogues were classified into different groups, ranging from very active auxins to not active. A halogen at the 4-position of the aromatic ring was important for auxin activity, whereas a halogen at the 3-position resulted in reduced activity. Moreover, a small substitution at the carboxylate chain was tolerated, as was extending the carboxylate chain with two but not with one carbon. In the process, we also identified two 2,4-D analogues as efficient inducers of adventitious root formation and several possible anti-auxins. The auxin activity of the 2,4-D analogues was consistent with their simulated TIR1-Aux/IAA coreceptor binding characteristics. A strong correlation was observed between SE induction efficiency and auxin activity, indicating that the stress-related effects triggered by 2,4-D that are considered important for SE induction are down-stream of auxin signaling.

plant biology↗

bioRxiv2021

Deep molecular characterization linked to drug response profiling of pancreatic ductal adenocarcinoma using patient-derived organoids.

Pancreatic ductal adenocarcinoma (PDAC) is characterized by high drug resistance and poor prognosis. Novel therapeutic and stratification strategies are urgently needed. Here, we present an integration of in-depth genomic and transcriptomic characterization with drug screening and clinical outcome based on a catalogue of 51 patient-derived tumor organoids (PDOs) from resected PDAC. Known PDAC molecular subtypes and their prognostic value are conserved in organoids. Integration of transcriptomic and drug response profiles suggest a metabolism-mediated modulations of drug resistance. Copy number alterations on chromosome 13q and wild-type status of TP53 emerged as potential novel genomic biomarkers for sensitivity to 5-FU and oxaliplatin treatment, respectively. Functional testing of targeted drugs in PDOs revealed its additional value for genome-driven personalized oncology. Co-deletion of TP53/POLR2A increased vulnerability to RNA polymerase II inhibition, pointing to a promising target for personalized treatment in PDAC. SignificancePatient-derived PDAC organoids hold great promise as surrogate tumor models for personalized oncology. By integrating highly granular molecular, drug sensitivity and clinical data, we demonstrate that PDOs are valid models for molecular characterization and response prediction that also enable identification of novel drug sensitivity biomarkers and resistance mechanisms in PDAC.

cancer biology↗

bioRxiv2021

Endogenous auxin directs development of embryonic stem cells into somatic proembryos in Arabidopsis

Somatic embryogenesis (SE) is the process by which embryos develop from in vitro cultured vegetative tissue explants. The synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) is widely used for SE induction, but SE can also be induced by overexpression of specific transcription factors, such as AT-HOOK MOTIF NUCLEAR LOCALIZED 15 (AHL15). 2,4-D and AHL15 both trigger the biosynthesis of the natural auxin indole-3-acetic acid (IAA). However, the role of this endogenously produced auxin in SE is yet not well understood. In this study we show that the induction of embryonic stem cells from explants does not require IAA biosynthesis, whereas an increase in IAA levels is essential to maintain embryo identity and for embryo formation from these stem cells. Further analysis showed that YUCCA (YUC) genes involved in the IPyA auxin biosynthesis pathway are up-regulated in embryo-forming tissues. Chemical inhibition of the IPyA pathway significantly reduced or completely inhibited the formation of somatic embryos in both 2,4-D-and AHL15-dependent systems. In the latter system, SE could be restored by exogenous IAA application, confirming that the biosynthesis-mediated increase in IAA levels is important. Our analyses also showed that PIN1 and AUX1 are the major auxin carriers that determine respectively auxin efflux and influx during SE. This auxin transport machinery is required for the proper transition of embryonic cells to proembryos and, later, for correct cell fate specification and differentiation. Taken together, our results indicate that auxin biosynthesis in conjunction with its polar transport are required during SE for multicellular somatic proembryo development and differentiation. One sentence summarySomatic embryogenesis in Arabidopsis requires auxin biosynthesis and polar auxin transport only after the acquisition of embryonic competence for somatic proembryo development and differentiation.

plant biology↗

bioRxiv2020

miR156-independent repression of the ageing pathway bylongevity-promoting AHL proteins in Arabidopsis

Plants age by transition through distinct developmental phases, with the juvenile- to adult vegetative and the adult vegetative to reproductive phase change as two consecutive important post-embryonic phase transitions. During the transition from the juvenile- to adult vegetative phase, also known as the vegetative phase change (VPC), many plants undergo specific morphological and physiological changes. In the model plant Arabidopsis thaliana (Arabidopsis), for example, the VPC is marked by clear heteroblastic changes in leaf shape and size and the appearance of trichomes on the abaxial side of leaves. The VPC and the vegetative to reproductive transition are promoted by the SQUAMOSA PROMOTOR BINDING PROTEIN-LIKE (SPL) family of transcription factors and repressed by miR156 and miR157 that target the SPL transcripts. Here we present data that the plant longevity promoting AT-HOOK MOTIF NUCLEAR LOCALIZED protein 15 (AHL15) and family members also repress the SPL-driven ageing pathway. Arabidopsis ahl loss-of-function mutants showed an accelerated VPC and flowering time, whereas AHL15 overexpression dramatically delayed the VPC and flowering time in both Arabidopsis and Nicotiana tabacum. Expression analysis and tissue-specific AHL15 overexpression revealed that AHL15 affects the VPC and flowering time directly through its expression in the shoot apical meristem and young leaves. In addition, we found evidence that AHL15 represses SPL gene expression in a miR156/157-independent manner. The juvenile traits of spl loss-of-function mutants appeared to be dependent on the enhanced expression of the AHL15 gene, providing evidence for a reciprocal negative feedback between AHL15 and SPL genes. Antagonistically to AHLs, SPLs promote axillary meristem (AM) maturation and thus prevent vegetative growth from these meristems by repressing AHL15 expression. Taken together, our results place AHL15 and family members at a central position in the SPL-driven ageing pathway as suppressors of the VPC, flowering time and AM maturation.

plant biology↗

bioRxiv2020

A novel pathway controlling cambium initiation and -activity via cytokinin biosynthesis in Arabidopsis

Plant secondary growth, also referred to as wood formation, includes the production of secondary xylem, which is derived from meristematic cambium cells embedded in vascular tissues. Despite the importance of secondary xylem in plant growth and wood formation, the molecular mechanism of secondary growth is not yet well understood. Here we identified an important role for the Arabidopsis thaliana (Arabidopsis) AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED 15 (AHL15) gene, encoding for a putative transcriptional regulator, in controlling vascular cambium activity and secondary xylem formation. Secondary xylem development was significantly reduced in inflorescence stems of the Arabidopsis ahl15 loss-of-function mutant, whereas AHL15 overexpression led to extensive secondary xylem formation. AHL15 expression under a vascular meristem-specific promoter also enhanced the amount of interfascicular secondary xylem. Moreover, AHL15 appeared to be required for the enhanced secondary xylem formation in the Arabidopsis double loss-of-function mutant of the SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1) and FRUITFULL (FUL) genes. A well-known central regulator of cambial activity is the plant hormone cytokinin. We showed that the expression of two cytokinin biosynthesis genes (ISOPENTENYL TRANSERASE (IPT) 3 and 7) is decreased in ahl15 loss-of-function mutant stems, whereas the secondary xylem deficiency in these mutant stems can be resorted by cambium-specific expression of the Agrobacterium tumefaciens IPT gene, indicating that AHL15 acts through the cytokinin pathway. These findings support a model whereby AHL15 acts as a central factor inducing vascular cambium activity downstream of SOC1 and FUL and upstream of IPT3, IPT7 and LOG4, LOG5 governing the rate of secondary xylem formation in Arabidopsis inflorescence stems.

plant biology↗

bioRxiv2020

An Arabidopsis AT-hook motif nuclear protein mediates somatic embryogenesis and coinciding genome duplication

Plant somatic cells can be reprogrammed to totipotent embryonic cells that are able to form differentiated embryos in a process called somatic embryogenesis (SE), by hormone treatment or through overexpression of certain transcription factor genes, such as BABY BOOM (BBM). Here we show that overexpression of the AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED 15 (AHL15) gene induces formation of somatic embryos on Arabidopsis thaliana seedlings in the absence of hormone treatment. During zygotic embryogenesis, AHL15 expression starts early in embryo development, and AH15 and other AHL genes are required for proper embryo patterning and development beyond the heart stage. Moreover, AHL15 and several of its homologs are upregulated and required for SE induction upon hormone treatment, and they are required for efficient BBM-induced SE as downstream targets of BBM. A significant number of plants derived from AHL15 overexpression-induced somatic embryos are polyploid. Polyploidisation occurs by endomitosis specifically during the initiation of SE, assumingly due to AHL15-mediated heterochromatin decondensation coinciding with the acquisition of embryonic competency in somatic plant cells.

plant biology↗

bioRxiv2020

A suppressor of axillary meristem maturation promotes longevity in flowering plants

Post embryonic development and growth of flowering plants are for a large part determined by the activity and maturation state of stem cell niches formed in the axils of leaves, the so-called axillary meristems (AMs)1,2. Here we identify a new role for the Arabidopsis AT-HOOK MOTIF CONTAINING NUCLEAR LOCALIZED 15 (AHL15) gene as a suppressor of AM maturation. Loss of AHL15 function accelerates AM maturation, whereas ectopic expression of AHL15 suppresses AM maturation and promotes longevity in Arabidopsis and tobacco. Together our results indicate that AHL15 expression acts as a key molecular switch, directly downstream of flowering genes (SOC1, FUL) and upstream of GA biosynthesis, in extending the plants lifespan by suppressing AM maturation.

plant biology↗