Biology subjects

Fowler, H.

Publications and source records attributed to Fowler, H..

3 recordsLinked to original sources

bioRxiv2024

Reconfigurable multi-component nanostructures built from DNA origami voxels

In cells, proteins rapidly self-assemble into sophisticated nanomachines. Bio-inspired self-assembly approaches, such as DNA origami, have achieved complex 3D nanostructures and devices. However, current synthetic systems are limited by lack of structural diversity, low yields in hierarchical assembly, and challenges in reconfiguration. Here, we develop a modular system of DNA origami voxels with programmable 3D connections. We demonstrate multifunctional pools of up to 12 unique voxels that can assemble into many shapes, prototyping 50 structures. Multi-step assembly pathways with sequential reduction in conformational freedom were then explored to increase yield. Voxels were first assembled into flexible chains and then folded into rigid structures, increasing yield 100-fold. Furthermore, programmable switching of local connections between flexible and rigid states achieved rapid and reversible reconfiguration of global structures. We envision that foldable chains of DNA origami voxels can be integrated with scalable assembly methods to achieve new levels of complexity in reconfigurable nanomaterials.

synthetic biology↗

bioRxiv2022

Integrated PET and confocal imaging informs a functional timeline for the dynamic process of vascular reconnection during grafting.

Grafting is a widely used agricultural technique that involves the physical joining of separate plant parts so they form a unified vascular system, enabling beneficial traits from independent genotypes to be captured in a single plant. This simple, yet powerful tool has been used for thousands of years to improve abiotic and biotic stress tolerance, enhance yield, and alter plant architecture in diverse crop systems. Despite the global importance and ancient history of grafting, our understanding of the fundamental biological processes that make this technique successful remains limited, making it difficult to efficiently expand on new genotypic graft combinations. One of the key determinants of successful grafting is the formation of the graft junction, an anatomically unique region where xylem and phloem strands connect between newly joined plant parts to form a unified vascular system. Here, we use an integrated imaging approach to establish a spatiotemporal framework for graft junction formation in the model crop Solanum lycopersicum (tomato), a plant that is commonly grafted worldwide to boost yield and improve abiotic and biotic stress resistance. By combining Positron Emission Tomography (PET), a technique that enables the spatio-temporal tracking of radiolabeled molecules, with high-resolution laser scanning confocal microscopy (LSCM), we are able to merge detailed, anatomical differentiation of the graft junction with a quantitative timeline for when xylem and phloem connections are functionally re-established. In this timeline, we identify a 72-hour window when anatomically connected xylem and phloem strands regain functional capacity, with phloem restoration typically preceding xylem restoration by about 24-hours. Furthermore, we identify heterogeneity in this developmental and physiological timeline that corresponds with microvariability in the physical contact between newly joined rootstock-scion tissues. Our integration of PET and confocal imaging technologies provides a spatio-temporal timeline that will enable future investigations into cellular and tissue patterning events that underlie successful versus failed vascular restoration across the graft junction.

plant biology↗

bioRxiv2018

Functional dissection of the ARGONAUTE7 promoter

ARGONAUTES are the central effector proteins of RNA silencing which bind target transcripts in a small RNA-guided manner. Arabidopsis thaliana has ten ARGONAUTE (AGO) genes, with specialized roles in RNA-directed DNA methylation, post-transcriptional gene silencing, and antiviral defense. To better understand specialization among AGO genes at the level of transcriptional regulation we tested a library of 1497 transcription factors for binding to the promoters of AGO1, AGO10, and AGO7 using yeast 1-hybrid assays. A ranked list of candidate DNA-binding TFs revealed binding of the AGO7 promoter by a number of proteins in two families: the miR156-regulated SPL family and the miR319-regulated TCP family, both of which have roles in developmental timing and leaf morphology. Possible functions for SPL and TCP binding are unclear: we showed that these binding sites are not required for the polar expression pattern of AGO7, nor for the function of AGO7 in leaf shape. Normal AGO7 transcription levels and function appear to depend instead on an adjacent 124-bp region. Progress in understanding the structure of this promoter may aid efforts to understand how the conserved AGO7-triggered TAS3 pathway functions in timing and polarity.

plant biology↗