Biology subjects

Merret, R.

Publications and source records attributed to Merret, R..

3 recordsLinked to original sources

bioRxiv2023

Cell type-specific control of secondary cell wall formation by Musashi-type translational regulators in Arabidopsis

Deciphering the mechanism of secondary cell wall/SCW formation in plants is key to understanding their development and the molecular basis of biomass recalcitrance. Although transcriptional regulation is essential for SCW formation, little is known about the implication of post-transcriptional mechanisms in this process. Here we report that two bonafide RNA-binding proteins homologous to the animal translational regulator Musashi, MSIL2 and MSIL4, function redundantly to control SCW formation in Arabidopsis. MSIL2/4 interactomes are similar and enriched in proteins involved in mRNA binding and translational regulation. MSIL2/4 mutations alter SCW formation in the fibers, leading to a reduction in lignin deposition, and an increase of 4-O-glucuronoxylan methylation. In accordance, quantitative proteomics of stems reveal an overaccumulation of glucuronoxylan biosynthetic machinery, including GXM3, in the msil2/4 mutant stem. We showed that MSIL4 immunoprecipitates GXM mRNAs, suggesting a novel aspect of SCW regulation, linking post-transcriptional control to the regulation of SCW biosynthesis genes.

plant biology↗

bioRxiv2022

High rates of spontaneous chromosomal duplications are compensated by translational regulation in a photosynthetic unicellular eukaryote

While duplications have long been recognized as a fundamental process driving major evolutionary innovations, direct estimations of spontaneous chromosome duplication rates, leading to aneuploid karyotypes, are scarce. Here, we provide the first estimations of spontaneous chromosome duplication rates in six unicellular eukaryotic species from mutation accumulation (MA) experiments. The spontaneous chromosome duplication rates reach 1x10-4 to 1x10-3 per genome per generation, which is ~4 to ~50 times less frequent than spontaneous point mutations per genome, whereas chromosome duplication events can affect 1 to 7% of the total genome size. Comparative transcriptomics between MA lines with different chromosome duplications reveals a strong positive correlation between RNA expression rate and DNA copy number. However, comparative analyses of the translation rate of mRNAs estimated by polysome profiling unravel a chromosome specific dosage compensation mechanism. In particular, one chromosome with a gene average of 2.1 excess of mRNAs is compensated by an average of ~0.7 decrease in translation rates. Altogether, our results are consistent with previous observations of a chromosome dependent effect of dosage compensation and provide evidence that it may occur during translation. These results support the existence of a yet unknown post-transcriptional mechanism orchestrating the modification of translation of hundreds of transcripts from genes located on duplicated regions in eukaryotes.

evolutionary biology↗

bioRxiv2021

RNA labelling in live plants reveals single cell transcriptional dynamics: application to phosphate signaling

Plants are sessile organisms constantly adapting to ambient fluctuations through spatial and temporal transcriptional responses. Here, we implemented the latest generation RNA imaging system and combined it with microfluidics to visualize transcriptional regulation in living Arabidopsis plants. This enabled quantitative measurements of the transcriptional activity of single loci in single cells, real time and changing environmental conditions. Using phosphate responsive genes as model, we found that active genes displayed high transcription initiation rates ([~]3s) and frequently clustered together in endoreplicated cells. We observed gene bursting and large allelic differences in single cells, revealing that at steady-state, intrinsic noise dominated extrinsic variations. Moreover, we established that transcriptional repression triggered in roots by phosphate, a crucial macronutrient limiting plant development, occurred with unexpected fast kinetics ([~]minutes) and striking heterogeneity between neighboring cells. Access to single cell RNA polymerase II dynamics within live plants will benefit future studies of signaling processes.

plant biology↗