Biology subjects

Luden, T.

Publications and source records attributed to Luden, T..

3 recordsLinked to original sources

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

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↗