Biology subjects

Platt, T. G.

Publications and source records attributed to Platt, T. G..

3 recordsLinked to original sources

bioRxiv2021

Gene loss during the transition to multicellularity

Multicellular evolution is a major transition associated with momentous diversification of multiple lineages and increased developmental complexity. The volvocine algae comprise a valuable system for the study of this transition, as they span from unicellular to undifferentiated and differentiated multicellular morphologies despite their genomes being highly similar, suggesting multicellular evolution requires few genetic changes to undergo dramatic shifts in developmental complexity. Here, the evolutionary dynamics of six volvocine genomes were examined, where a gradual loss of genes was observed in parallel to the co-option of a few key genes. Protein complexes in the six species exhibited a high degree of novel interactions, suggesting that gene loss plays a role in evolutionary novelty. This finding was supported by gene network modeling, where gene loss outpaces gene gain in generating novel stable network states. These results suggest developmental complexity may be driven by gene loss, and not just by gene gain. Significance StatementIncreased developmental complexity is thought to evolve mainly through genetic innovation and co-option. Comparison of the genomes of the closely related volvocines revealed that despite large changes in developmental complexity their genomes are exhibiting significant gene loss. Further, a burst of gene loss is shown to occur at the transition to undifferentiated multicellularity by gene inactivation and decay. This likely results in changes to protein-protein interactions within the cell, suggesting evolutionary novelty does not always require gene gain. Using empirical and modelling approaches we demonstrate gene loss can more easily produce protein network novelty than gene gain. We propose that gene loss can be a driver of biological innovation, allowing for reconfiguration of gene networks and differential use of existing functional repertoires.

evolutionary biology↗

bioRxiv2020

Simultaneous Discovery of Positive and Negative Interactions Among Root Microbiome Bacteria Using Microwell Recovery Arrays

Understanding the consequences of microbe-microbe interactions is critical in efforts to predict the function of microbiomes and to manipulate or construct communities to achieve desired outcomes. The investigation of these interactions poses a significant challenge - in part due to the lack of suitable experimental tools. We present the Microwell Recovery Array, a high throughput approach designed to rapidly screen interactions across a microbiome and uncover higher-order combinations of strains that either inhibit or promote the function of a GFP-producing focal species. One experiment generates 104 unique microbial communities that contain a focal species combined with a unique combination of previously uncharacterized cells from plant rhizosphere. Cells are then sequentially extracted from individual co-culture wells that display highest or lowest levels of focal species function using a novel high-resolution photopolymer extraction system. Microbes present are subsequently identified and the putative interactions are validated. Using this approach, we screen the Populus trichocarpa rhizosphere for bacterial strains affecting the survival and growth of Pantoea sp. YR343, a plant growth promoting strain isolated from the P. trichocarpa rhizosphere. We were able to simultaneously isolate and validate multiple Stenotrophomonas strains that antagonize strain YR343 growth and a set of Enterobacter strains that promote strain YR343 growth. The latter demonstrates the unique ability of the platform to uncover multi-membered consortia that generate emergent phenotypes. This knowledge will inform the development of beneficial consortia that promote the production of Populus biofuel feedstock, while the platform is adaptable to screening higher-order interactions in any microbiome of interest. Significance StatementAchieving a fundamental understanding of microbe-microbe interactions that occur within microbial communities is a grand challenge in microbiology due to the limited experimental tools available. In this report, we describe a new tool that enables one to screen microbial interactions across thousands of compositionally unique communities to discover collections of bacteria that antagonize or promote the survival and growth of bacteria with important functions. This approach has the unique ability to uncover higher-order combinations of bacteria that generate emergent phenotypes, information useful for development of biofertilizer, biocontrol, or probiotic consortia, as well as in the design of communities for biosynthetic compound production.

bioengineering↗

bioRxiv2019

Destabilization of the tumor-inducing plasmid from an octopine-type Agrobacterium tumefaciens lineage drives a large deletion in the co-resident At megaplasmid

Bacteria with multi-replicon genome organizations, including members of the family Rhizobiaceae, often carry a variety of niche-associated functions on large plasmids. While evidence exists for cross-replicon interactions and co-evolution between replicons in many of these systems, remarkable strain-to-strain variation is also observed for extrachromosomal elements, suggesting increased genetic plasticity. Here, we show that curing of the tumor-inducing virulence plasmid (pTi) of an octopine-type Agrobacterium tumefaciens lineage leads to a large deletion in the co-resident At megaplasmid (pAt). The deletion event is mediated by a repetitive IS-element, IS66, and results in a variety of environment-dependent fitness consequences, including loss of independent conjugal transfer of the plasmid. Interestingly, a related and otherwise wild-type A. tumefaciens strain is missing exactly the same large pAt segment as the pAt deletion derivatives, suggesting a similar event over its natural history. Overall, the findings presented here uncover a novel genetic interaction between the two large plasmids of A. tumefaciens and provide evidence for cross-replicon integration and co-evolution of these plasmids.

microbiology↗