Biology subjects

Geilfus, C.-M.

Publications and source records attributed to Geilfus, C.-M..

3 recordsLinked to original sources

bioRxiv2024

Application of cryo-FIB-SEM for investigating organelle ultrastructure in guard cells of higher plants

Stomata are vital for CO2 and water vapor exchange, with guard cells aperture and ultrastructure highly responsive to environmental cues. However, traditional methods for studying guard cell ultrastructure, which rely on chemical fixation and embedding, often distort cell morphology and compromise membrane integrity, leaving no suitable methodology until now. In contrast, plunge-freezing in liquid ethane rapidly preserves cells in a near-native vitreous state for cryogenic electron microscopy. Using this approach, we applied Cryo-Focused Ion Beam-Scanning Electron Microscopy (cryo- FIB-SEM) to study the guard cell ultrastructure of Vicia faba, a higher plant model chosen for its sensitivity to external factors and ease of epidermis isolation, advancing beyond previous cryo-FIB-SEM applications in lower plant algae. The results firstly introduced cryo-FIB-SEM volume imaging, enabling subcellular ultrastructure visualization of higher plants like V. faba in a vitrified, unaltered state. 3D models of organelles such as stromules, chloroplast protrusions, chloroplasts, starch granules, mitochondria, and vacuoles were reconstructed from cryo-FIB-SEM volumetric data, with their surface area and volume initially determined using manual segmentation. Future studies using this near-native volume imaging technique hold promise for investigating how environmental factors like drought or salinity influence stomatal behavior and the morphology of guard cells and their organelles.

plant biology↗

bioRxiv2024

Date palm acclimates to aridity by diverting organic osmolytes for root osmotic adjustment in parallel with leaf membrane remodeling and ROS scavenging

Highlight statementOsmotic strength of date palm roots increases with soil desiccation, for which the accumulation of organic osmolytes, such as sugars, is essential in complement to energetically cheap mineral osmotics. Date palm (Phoenix dactylifera L.) is an important crop in arid regions that is well-adapted to desert ecosystems. To understand the remarkable ability to grow and yield in water-limited environments, experiments were conducted in a simulated desert environment with water-withholding for up to four weeks. In response to drought, root, rather than leaf, osmotic strength increased, with sugars contributing more to the osmolyte increase than minerals. Consistently, carbon and amino acid metabolism was acclimated toward biosynthesis at both the transcriptional and translational levels. In leaves, a remodeling of membrane systems was observed, suggesting changes in thylakoid lipid composition, which together with the restructuring of the photosynthetic apparatus, indicated an acclimation preventing oxidative damage. Thus, xerophilic date palm avoids oxidative damage under drought by combined prevention and rapid detoxification of oxygen radicals. Although minerals were expected to serve as cheap key osmotics, date palm also relies on organic osmolytes for osmotic adjustment of the roots during desiccation. The diversion of these resources away from growth is consistent with date palms strategy of generally slow growth in harsh environments and clearly indicates a trade-off between growth and stress-related physiological responses.

plant biology↗

bioRxiv2023

In planta exploitation of leaf apoplastic compounds: a window of opportunity for spatiotemporal studies of apoplastic metabolites, hormones and physiology

Processes in the leaf apoplast are relevant for development, cell wall rheological properties, plant nutrition, sink-source portioning, microbe-host plant-interactions or intercellular information exchange and signaling and are therefore regulated or influenced by the composition of the leaf apoplastic solute. In contrast to the traditional methods for the extraction of apoplastic solutes that are more or less destructive, we propose a new method that allows extraction of leaf apoplastic solutes (i) non-invasively and, thus, (ii) over time. Moreover, the method has (iii) a high spatial resolution that allows identification of solute-microdomains in the leaf apoplast. The method was established for Arabidopsis thaliana and Vicia faba leaves but should also be applicable to other plants species with similar leaf morphologies. It is based on the infiltration of an aqueous extraction solution into the apoplast followed by its recovery seconds later, both through the stomata. By this, the apoplast (and its solutes) of an identical leaf can be sampled on successive days with negligible symplastic contamination. A spatiotemporal mapping of leaf apoplastic ion and metabolite patterns within the identical leaf opens a window of opportunity for understanding apoplast biology. As for example, the existence of apoplastic abscisic acid gradients within a leaf in response to salinity was witnessed in this study, as was the unsuspected accumulation of kaempferol glycosides in the leaf apoplast. The presented method is relevant for plant developmental biologists, phytopathologists, plant physiologists, plant nutritionists and others that need to integrate apoplast biology into their research approaches.

plant biology↗