Biology subjects

Moeller, B.

Publications and source records attributed to Moeller, B..

3 recordsLinked to original sources

bioRxiv2026

Myosin-Driven Nuclear Movement Generates Stromules in Arabidopsis thaliana

Plastids form stroma-filled tubular extensions, termed stromules, that are implicated in inter-organellar communication. In pathogen-challenged Nicotiana benthamiana, stromule formation is driven by kinesins acting along microtubules. However, whether this mechanism also operates in unstressed plants or in other species remains unknown. Using systematic genetic analysis of all class XI myosin genes and quantitative time-lapse imaging in Arabidopsis (Arabidopsis thaliana), we show that basal stromule formation is predominantly myosin dependent through two distinct mechanisms. Myosin XI-I generates most stromules by driving oscillatory nuclear movement that mechanically pulls stromules from stationary plastids within the approx. 8m wide stromule-promoting zone. Myosins XI-K, XI-1, and XI-2 additionally drive a movement-independent, nucleus-associated stromule subpopulation within the same zone, establishing two mechanistically distinct pathways. We propose that movement-coupled stromules function as dynamic tethers maintaining plastid-nucleus proximity during nuclear oscillations, while movement-independent stromules expand the plastid membrane area within the perinuclear space, increasing the potential contact surface with the nucleus and surrounding environment. Together, both populations are proposed to enhance signal and metabolite exchange at the plastid-nucleus interface. These findings indicate that stromule biogenesis is both mechanistically and functionally context dependent, challenging the universality of the kinesin-microtubule model across plant species and physiological states.

plant biology↗

bioRxiv2019

rhizoTrak: A flexible open source Fiji plugin for user-friendly manual annotation of time-series images from minirhizotrons

Background and aimsMinirhizotrons are commonly used to study root turnover which is essential for understanding ecosystem carbon and nutrient cycling. Yet, extracting data from minirhizotron images requires intensive annotation effort. Existing annotation tools often lack flexibility and provide only a subset of the required functionality. To facilitate efficient root annotation in minirhizotrons, we present the user-friendly open source tool rhizoTrak. Methods and resultsrhizoTrak builds on TrakEM2 and is publically available as Fiji plugin. It uses treelines to represent branching structures in roots and assigns customizable status labels per root segment. rhizoTrak offers configuration options for visualization and various functions for root annotation mostly accessible via keyboard shortcuts. rhizoTrak allows time-series data import and particularly supports easy handling and annotation of time series images. This is facilitated via explicit temporal links (connectors) between roots which are automatically generated when copying annotations from one image to the next. rhizoTrak includes automatic consistency checks and guided procedures for resolving conflicts. It facilitates easy data exchange with other software by supporting open data formats. ConclusionsrhizoTrak covers the full range of functions required for user-friendly and efficient annotation of time-series images. Its flexibility and open source nature will foster efficient data acquisition procedures in root studies using minirhizotrons.

plant biology↗

bioRxiv2018

Microtubule-associated protein IQ67 DOMAIN5 regulates interdigitation of leaf pavement cells in Arabidopsis thaliana

Plant microtubules form a highly dynamic intracellular network with important roles for regulating cell division, cell proliferation and cell morphology. Its organization and dynamics are coordinated by various microtubule-associated proteins (MAPs) that integrate environmental and developmental stimuli to fine-tune and adjust cytoskeletal arrays. IQ67 DOMAIN (IQD) proteins recently emerged as a class of plant-specific MAPs with largely unknown functions. Here, using a reverse genetics approach, we characterize Arabidopsis IQD5 in terms of its expression domains, subcellular localization and biological functions. We show that IQD5 is expressed mostly in vegetative tissues, where it localizes to cortical microtubule arrays. Our phenotypic analysis of iqd5 loss-of-function lines reveals functions of IQD5 in pavement cell (PC) shape morphogenesis, as indicated by reduced interdigitation of neighboring cells in the leaf epidermis of iqd5 mutants. Histochemical analysis of cell wall composition further suggests reduced rates of cellulose deposition in anticlinal cell walls, which correlate with reduced asymmetric expansion. Lastly, we provide evidence for IQD5-dependent recruitment of calmodulin calcium sensors to cortical microtubule arrays. Our work thus identifies IQD5 as a novel player in PC shape regulation, and, for the first time, links calcium signaling to developmental processes that regulate multi-polar growth in PCs.\n\nHighlightMicrotubule-localized Arabidopsis IQ67 DOMAIN5 regulates pavement cell morphogenesis in the leaf epidermis and links calcium-calmodulin signaling to lobe initiation and asymmetric expansion during early phases of interdigitated cell growth.

plant biology↗