Biology subjects

Pratt, A.

Publications and source records attributed to Pratt, A..

3 recordsLinked to original sources

bioRxiv2026

Small RNA-guided transgene repression systems enable toxic gene cloning in bacteria

Multiple vectors and bacterial strains have been developed to enable cloning and amplification of DNA plasmids used in bioengineering applications when transgenic components are toxic to the host. These include plasmids that limit readthrough transcription into transgenic sequences and host strains carrying mutations to minimize recombination or plasmid copy number. However, these techniques are insufficient in cases where transgene expression elements are recognized by the bacterial transcriptional apparatus, or the translation products have functions in cellular metabolism. Here we demonstrate two platforms that mitigate bacterial expression of transgenes driven by the prokaryotic-like promoters of chloroplast transgenes destined for use in plant plastid genetic engineering applications. Both an engineered CRISPRi approach and utilization of the native E. coli Hfq repression system resulted in significant knockdown of plasmid-borne transgene expression, resulting in reproducibly successful cloning and plasmid amplification. The advancements reported here will facilitate synthetic biology studies generally, and enable complex transgenic studies in prokaryotic-like organelles.

molecular biology↗

bioRxiv2025

Functional relocation of the maize chloroplast atpB gene to the nucleus restores photosynthetic competence to a gene-edited non-photosynthetic mutant

We present a novel approach to photosynthetic gene engineering in maize using a nuclear-encoded, chloroplast-targeted TALE-cytidine deaminase enzyme to create non-photosynthetic knockout mutants of the chloroplast rbcL gene. An off-target mutation in the adjacent atpB gene, encoding the {beta} subunit of ATP synthase, was consistently found in all edited lines, identified as pigment-deficient in tissue culture. These double mutants, carrying mutations in both genes, were purified to homoplasmy using unique leaf-base regeneration techniques. To test mutation complementation and identify the causal gene, nuclear transgenic lines expressing chloroplast-targeted RbcL and AtpB proteins were generated. The results show that nuclear expression of AtpB restores chlorophyll accumulation and supports wild-type growth in tissue culture.

plant biology↗

bioRxiv2019

Extensive Evaluation of Weighted Ensemble Strategies for Calculating Rate Constants and Binding Affinities of Molecular Association/Dissociation Processes

The weighted ensemble (WE) path sampling strategy is highly efficient in generating pathways and rate constants for rare events using atomistic molecular dynamics simulations. Here we extensively evaluated the impact of several advances to the WE strategy on the efficiency of computing association and dissociation rate constants (kon, koff) as well as binding affinities (KD) for a set of benchmark systems, listed in order of increasing timescales of molecular association/dissociation processes: methane/methane, Na+/Cl-, and K+/18-crown-6 ether. In particular, we assessed the advantages of carrying out (i) a large set of \"light-weight\" WE simulations that each consist of a small number of trajectories vs. a single \"heavy-weight\" WE simulation that consists of a relatively large number of trajectories, (ii) equilibrium vs. steady-state WE simulations, (iii) history augmented Markov State Model (haMSM) post-simulation analysis of equilibrium sets of trajectories, and (iv) tracking of trajectory history (the state last visited) during the dynamics propagation of equilibrium WE simulations. Provided that state definitions are known in advance, our results reveal that heavy-weight, steady-state WE simulations are the most efficient protocol for calculating kon, koff, and KD values. If states are not strictly defined in advance, heavy-weight, equilibrium WE simulations are the most efficient protocol. This efficiency can be further improved with the inclusion of trajectory history during dynamics propagation. In addition, applying the haMSM post-simulation analysis enhances the efficiency of both steady-state and equilibrium WE simulations. Recommendations of appropriate WE protocols are made according to the goals of the simulations (e.g. to efficiently calculate rate constants and/or generate a diverse set of pathways).

biophysics↗