Trehin, C. | Search bioRxiv

bioRxiv2024

Sepal shape variability is robust to cell size heterogeneity in Arabidopsis

How organisms produce organs with robust shapes and sizes is still an open question. In recent years, the Arabidopsis sepal has been used as a model system to study this question because of its highly reproducible shape and size. One interesting aspect of the sepal is that its epidermis contains cells with very different sizes. Previous reports had qualitatively shown that sepals with more or less giant cells exhibit comparable final size and shape. Here we investigate this question using quantitative approaches. We find that a mixed population of cell size modestly contribute to the normal width of the sepal, but is not essential for its shape robustness. Furthermore, in a mutant with increased cell and organ growth variability, the change in final sepal shape caused by giant cells is exaggerated, but the shape robustness is not affected. This formally demonstrates that sepal shape variability is robust to cell size heterogeneity. Main conclusionA mixed population of cells with varied sizes plays a limited role in ensuring the symmetrical shape of the sepal, and is not essential for sepal shape robustness in Arabidopsis.

plant biology↗

bioRxiv2022

Paf1C denoises transcription and growth patterns to achieve organ shape reproducibility

In multicellular systems, all cells exhibit transcriptional noise. However, its exact contribution to morphogenesis often remains unclear, especially in animals where cells can also move. Here we take advantage of walled plant cells, where transcriptional noise happens in tissues with a fixed topology. Using synchronously growing guard cells in stomata, we demonstrate that mutation in VIP3, a subunit of the conserved polymerase-associated factor 1 complex (Paf1C), increases transcriptional noise in Arabidopsis. This conclusion could be generalized to other group of cells at the shoot apex. Such noise translates into growth and shape defects. Indeed, in vip3 sepals, we measured higher growth heterogeneity between adjacent cells, with molecular evidence of increased local mechanical conflicts. This even culminated with the presence of negatively growing cells in specific growth conditions. Interestingly, such increased local noise makes the regional pattern of growth less clear-cut. Reduced regional conflicts lead to delay in organ growth arrest, ultimately making final organ shapes and sizes more variable. We propose that transcriptional noise is managed by Paf1C to ensure organ robustness by building up mechanical conflicts at the regional scale, instead of the local scale. HIGHLIGHTSO_LIPaf1C controls transcriptional noise in Arabidopsis C_LIO_LIPaf1C reduces growth heterogeneity and dampens local mechanical conflicts C_LIO_LIImpairing both Paf1C and microtubules can trigger negative growth in Arabidopsis C_LIO_LIScaling up local conflicts to regional ones with sharp boundaries contributes to organ shape robustness C_LI

developmental biology↗