A “bright” new map of the bryophyte development
All plants on land undergo a unique reproductive cycle, alternating between generations. Unlike vascular plants, bryophytes—a group encompassing liverworts, mosses, and hornworts—feature a dominant haploid phase, with only one copy of each chromosome. This fundamental difference influences how these multicellular organisms grow. Yet, our understanding of bryophyte biology remains limited compared to that of crops and flowering plants. The emergence of new model systems, such as the liverwort Marchantia, the moss Physcomitrium, and the hornwort Anthoceros, has opened avenues for comprehending plant evolution, which were unimaginable decades ago.
A systems biology approach
In a ground-breaking study just published in The Plant Cell, researchers from the Haseloff lab adopted a systems biology approach to identify cellular identities during Marchantia growth. Typically, combinations of various transcription factor genes determine cell and tissue identities in multicellular organisms. Leveraging this knowledge, the researchers extracted regulatory elements from Marchantia's transcription factor genes, synthesized them, and generated reporter lines for each element. This involved transforming hundreds of transgenic plants to cover the diversity of tissues and expression patterns. Subsequently, they imaged the reporters at different developmental stages and curated a public database of fluorescent images. Analysing these images enabled them to construct a highly detailed map of cellular identities.
OpenPlant
"The OpenPlant collection of TF promoters and cellular map for Marchantia gemma, are part of an epic project guided by Facundo Romani and Susana Sauret-Güeto (now in the Crop Science Centre). It has produced an extensive new resource for linking gene expression and cellular microarchitecture in Marchantia” said Prof. Jim Haseloff.
The collection of plasmids are available to researchers worldwide along with other resources generated by the OpenPlant Synthetic Biology Research Centre, funded by the BBSRC and EPSRC. The genetic tools described in this paper provide modular building blocks for in vivo imaging, can be combined to report multiple cellular states at the same time, and reused for future research. The potential applications extend from fundamental biological studies to plant bioproduction and engineering.
First author on the paper, Facundo Romani, said: "This work is part of a project that spanned several years and the work of many former and current researchers and PhD students. The pioneering work led by Susana Sauret-Güeto created the basis for building this map. Surveying the expression patterns of Marchantia promoters required development of new quantitative approaches. There are very few examples of so many stable transgenic lines being generated for a single project. With the advances and insights gained from this paper, we can face future projects much more easily".
Susana Sauret-Gueto said: “I am excited that the pipeline put in place to manage the data on the whole Marchantia promoter collection, constructs, lines and images, has been key in facilitating teamwork and supporting the design-build-test-learn cycle. Thus enabling the generation of this extensive resource on reporters for cellular types which will help addressing challenging questions on the self-organisation of all multicellular organisms.”
The paper also incorporates contributions from Prof. John Bowman’s group in Monash University. It was funded by BBSRC, EPSRC, and the Australian Research Council.
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For more information
Please contact first author Facundo Romani