Coiro, M. | bioRxiv Science

bioRxiv2024

Beyond the phloem: A general role of the Arabidopsis OCTOPUS gene family in controlling plant growth vigour

OCTOPUS (OPS) and OCTOPUS-LIKE 2 (OPL2), two homologous genes, were previously identified as important regulators of phloem differentiation in Arabidopsis roots, impacting root growth when their function is lost. Here, we investigated the roles of the other three OPS homologs in Arabidopsis, OPL1, OPL3, and OPL4. We employed promoter activity analyses, protein localisation studies, functional complementation assays, analysis of single and multiple mutant combinations, and growth assays, including exposure to CLE45 and brassinosteroid pathway modulators. The OPS/OPL genes exhibit overlapping expression patterns and functions. Multiple mutant combinations revealed a high degree of redundancy, with OPS and the phloem domain playing a major role in controlling plant growth. While phloem phenotypes are not exacerbated in higher-order mutants, plant growth vigour is nevertheless more severely impacted than in ops opl2. Our results suggest a novel role of the OPS/OPL genes in broadly controlling plant growth and development, potentially through the modulation of meristematic activity via brassinosteroid pathways.

plant biology↗

bioRxiv2017

Experimental signal dissection and method sensitivity analyses reaffirm the potential of fossils and morphology in the resolution of seed plant phylogeny

The placement of angiosperms and Gnetales in seed plant phylogeny remains one of the most enigmatic problems in plant evolution, with morphological analyses (which have usually included fossils) and molecular analyses pointing to very distinct topologies. Almost all morphology-based phylogenies group angiosperms with Gnetales and certain extinct seed plant lineages, while most molecular phylogenies link Gnetales with conifers. In this study, we investigate the phylogenetic signal present in published seed plant morphological datasets. We use parsimony, Bayesian inference, and maximum likelihood approaches, combined with a number of experiments with the data, to address the morphological-molecular conflict. First, we ask whether the lack of association of Gnetales with conifers in morphological analyses is due to an absence of signal or to the presence of competing signals, and second, we compare the performance of parsimony and model based approaches with morphological datasets. Our results imply that the grouping of Gnetales and angiosperms is largely the result of long branch attraction, consistent across a range of methodological approaches. Thus, there is a signal for the grouping of Gnetales with conifers in morphological matrices, but it was swamped by convergence between angiosperms and Gnetales, both situated on long branches. However, this effect becomes weaker in more recent analyses, as a result of addition and critical reassessment of characters. Even when a clade including angiosperms and Gnetales is still weakly supported by parsimony, model-based approaches favor a clade of Gnetales and conifers, presumably because they are more resistant to long branch attraction. Inclusion of fossil taxa weakens rather than strengthens support for a relationship of angiosperms and Gnetales. Our analyses finally reconcile morphology with molecules in favoring a relationship of Gnetales to conifers, and show that morphology may therefore be useful in reconstructing other aspects of the phylogenetic history of the seed plants.

evolutionary biology↗