Biology subjects

Trozzi, N.

Publications and source records attributed to Trozzi, N..

4 recordsLinked to original sources

bioRxiv2026

Maintenance of the leaf cell proliferation boundary by a cell size at division threshold mechanism.

The sizes and shapes of organs are established by the combined actions of cell proliferation and cell growth. In plants, development of the determinate planar leaf is initiated by primordia formation and establishment of abaxial/adaxial polarity [1,2,3]. Lamina outgrowth is driven by cell division and growth along proximo-distal (PD) and medio-lateral (ML) axes [4], established by mutually repressive PD gradients of miRNA and target transcription factors [5,6,7,8]. These gradients generate proximal regions of competence for cell division and increased growth, with distal regions of reduced growth, endoreduplication and differentiation. The transition from proliferation to growth and differentiation is marked by a cell cycle arrest front, which moves basipetally during leaf growth, progressively restricting proximal proliferative zones as the leaf grows [9,10,11]. Intersection of proximal proliferation-promoting gradients with distal differentiation-promoting gradients may delineate the arrest front, but its dynamics remain poorly understood. We reasoned that mutants affecting cell proliferation patterns may provide insights into the formation, maintenance and dissolution of the arrest front. Spatio-temporal modelling of live imaging data of loss of function mutants of the regulatory peptidase DA1 and its E3 ligase activator Big Brother (BB), which increase cell proliferation [12,13], showed that these proteins effectively establish a threshold cell size at division as a function of distance from the base of the growing leaf and the duration of growth. Loss of BB and DA1 activities increased the persistence of cell divisions and dissolved the arrest front. This suggested that the arrest front emerges from the interactions of threshold areas of cell division with the cessation of division over time, and not from an independently-specified boundary.

plant biology↗

bioRxiv2023

Puzzle cell shape emerges from the interaction of growth with mechanical constraints

Puzzle-shaped epidermal cells not only reduce mechanical stress during organ growth but also record the expansion history of the tissue in their outlines. By combining mechanical simulations with time-lapse imaging, we show that transitions from directional to isotropic expansion induce new lobes to form along the previous growth axis, and that switching the order of anisotropic and isotropic phases yields hybrid shapes that reliably preserve those transitions. In maize, model predictions and live imaging coincide precisely, and in Ara-bidopsis, final lobe patterns correlate more with growth history than with cell size alone. Ge-netic or pharmacological disruption of lobe formation constrains leaf expansion or drives compensatory elongation, which underscores a mechanical function. A broad survey of living and fossil vascular plants reveals that the mechanism to make puzzle-shaped cells is both widespread and developmentally plastic, suggesting that single snapshots of leaves can give insight into their growth history. Together, these findings demonstrate that puzzle cells trans-form cell geometry into a living record of how tissues grow.

plant biology↗

bioRxiv2021

MorphoGraphX 2.0: Providing context for biological image analysis with positional information

Positional information is a central concept in developmental biology. In developing organs, positional information can be idealized as a local coordinate system that arises from morphogen gradients controlled by organizers at key locations. This offers a plausible mechanism for the integration of the molecular networks operating in individual cells into the spatially-coordinated multicellular responses necessary for the organization of emergent forms. Understanding how positional cues guide morphogenesis requires the quantification of gene expression and growth dynamics in the context of their underlying coordinate systems. Here we present recent advances in the MorphoGraphX software (Barbier de Reuille et al. eLife 2015;4:e05864) that implement a generalized framework to annotate developing organs with local coordinate systems. These coordinate systems introduce an organ-centric spatial context to microscopy data, allowing gene expression and growth to be quantified and compared in the context of the positional information thought to control them.

developmental biology↗

bioRxiv2019

Lateral organ diversification in plants mediated by the ALOG protein family of transcription factors

Land plant shoot structures evolved a diversity of lateral organs as morphological adaptations to the terrestrial environment, in which lateral organs independently evolved in each lineage in the sporophyte or gametophyte generation. The gametophyte meristem of the basally-diverging plant Marchantia polymorpha produces axes with non-photosynthetic scale-like lateral organs instead of leaves. Here we report that an ALOG (Arabidopsis LSH1 and Oryza G1) family protein in Marchantia, MpTAWAWA1 (MpTAW1), regulates meristem maintenance and lateral organ development. A mutation in MpTAW1, preferentially expressed in lateral organs, induces lateral organs with mis-specified identity and increased cell number, and furthermore, causes defects in apical meristem maintenance. Remarkably, MpTAW1 expression rescued the elongated-spikelet phenotype of a rice mutant of MpTAW1 homologue. This suggests that ALOG genes are co-opted to specify lateral organ identities in both gametophyte and sporophyte shoots by repressing lateral organ growth. We propose that the recruitment of ALOG-mediated lateral organ modification was in part responsible for the convergent evolution of independently-evolved lateral organs among highly divergent plant lineages and contributed to the morphological diversification of land plants.

plant biology↗