Analyzing subcellular reorganization during early Arabidopsis embryogenesis using fluorescent markers

Virtually all growth, developmental, physiological, and defense responses in plants are accompanied by reorganization of subcellular structures to enable altered cellular growth, differentiation or function. Visualizing cellular reorganization is therefore critical to understand plant biology at the cellular scale. Fluorescently labeled markers for organelles, or for cellular components are widely used in combination with confocal microscopy to visualize cellular reorganization. Early during plant embryogenesis, the precursors for all major tissues of the seedling are established, and in Arabidopsis, this entails a set of nearly invariant switches in cell division orientation and directional cell expansion. Given that these cellular reorganization events are genetically regulated and coupled to formative events in plant development, they offer a good model to understand the genetic control of cellular reorganization in plant development. Until recently, it has been challenging to visualize subcellular structures in the early Arabidopsis embryo for two reasons: embryos are deeply embedded in seed coat and fruit, and in addition, no dedicated fluorescent markers, expressed in the embryo, were available. We recently established both an imaging approach and a set of markers for the early Arabidopsis embryo. Here, we describe a detailed protocol to use these new tools in imaging cellular reorganization.</p

A mass-spring model unveils the morphogenesis of phototrophic Diatoma biofilms

Diatoms often dominate planktonic communities in the ocean and phototrophic biofilms in streams and rivers, greatly contributing to global biogeochemical fluxes. In pelagic ecosystems, these microscopic algae can form chain-like microcolonies, which seem advantageous for nutrient uptake and protect against grazing, and at the same time reduce sinking. Despite the capability of many diatoms to form chains, their contribution to the architecture of phototrophic biofilms remains elusive. Here we propose a computational model to simulate the growth and behaviour of Diatoma chains in contrasting flow environments. This mass-spring mechanical model captures the natural behaviour of Diatoma chains well, emphasising the relevance of chain growth and entanglement for biofilm morphogenesis. The model qualitatively describes formation of intricate dome-shaped structures and of dreadlock-type streamers as observed in nature in multidirectional and unidirectional flow, respectively. The proposed model is a useful tool to study the effect of fluid dynamics on biofilm morphogenesis.BT/BiotechnologyApplied Science

YET ANOTHER INTRODUCTION TO ROUGH PATHS

This article provides another point of view on the theory of rough paths, which starts with simple considerations on ordinar

CLE25 peptide regulates phloem initiation in Arabidopsis through a CLERK-CLV2 receptor complex

The phloem, located within the vascular system, is critical for delivery of nutrients and signaling molecules throughout the plant body. Although the morphological process and several factors regulating phloem differentiation have been reported, the molecular mechanism underlying its initiation remains largely unknown. Here, we report that the small peptide-coding gene, CLAVATA 3 (CLV3)/EMBEYO SURROUNDING REGION 25 (CLE25), the expression of which begins in provascular initial cells of 64-cell-staged embryos, and continues in sieve element-procambium stem cells and phloem lineage cells, during post-embryonic root development, facilitates phloem initiation in Arabidopsis. Knockout of CLE25 led to delayed protophloem formation, and in situ expression of an antagonistic CLE25(G6T) peptide compromised the fate-determining periclinal division of the sieve element precursor cell and the continuity of the phloem in roots. In stems of CLE25(G6T) plants the phloem formation was also compromised, and procambial cells were over-accumulated. Genetic and biochemical analyses indicated that a complex, consisting of the CLE-RESISTANT RECEPTOR KINASE (CLERK) leucine-rich repeat (LRR) receptor kinase and the CLV2 LRR receptor-like protein, is involved in perceiving the CLE25 peptide. Similar to CLE25, CLERK was also expressed during early embryogenesis. Taken together, our findings suggest that CLE25 regulates phloem initiation in Arabidopsis through a CLERK-CLV2 receptor complex