Long-term single-cell imaging and simulations of microtubules reveal principles behind wall patterning during proto-xylem development

René Schneider,Jasper Van Der Gucht,Staffan Persson,Kris Van’T Klooster,Tijs Ketelaar,Taku Demura,Marcel Janson,Arun Sampathkumar,Kelsey L Picard,Eva E Deinum

doi:10.1038/s41467-021-20894-1

Abstract

Plants are the tallest organisms on Earth; a feature sustained by solute-transporting xylem vessels in the plant vasculature. The xylem vessels are supported by strong cell walls that are assembled in intricate patterns. Cortical microtubules direct wall deposition and need to rapidly re-organize during xylem cell development. Here, we establish long-term live-cell imaging of single Arabidopsis cells undergoing proto-xylem trans-differentiation, resulting in spiral wall patterns, to understand microtubule re-organization. We find that the re-organization requires local microtubule de-stabilization in band-interspersing gaps. Using microtubule simulations, we recapitulate the process in silico and predict that spatio-temporal control of microtubule nucleation is critical for pattern formation, which we confirm in vivo. By combining simulations and live-cell imaging we further explain how the xylem wall-deficient and microtubule-severing KATANIN contributes to microtubule and wall patterning. Hence, by combining quantitative microscopy and modelling we devise a framework to understand how microtubule re-organization supports wall patterning.

Highlights

Plants are the tallest organisms on Earth; a feature sustained by solute-transporting xylem vessels in the plant vasculature
We found that several microtubule bands and spirals formed simultaneously over the entire cell cortex, including the backside of the cells (Supplementary Fig. 1f)
Microtubule patterns form the template for the deposition of cell wall components, which are typified during xylem differentiation

Summary

Introduction

Plants are the tallest organisms on Earth; a feature sustained by solute-transporting xylem vessels in the plant vasculature. The xylem vessels are supported by strong cell walls that are assembled in intricate patterns. Cortical microtubules direct wall deposition and need to rapidly re-organize during xylem cell development. We establish long-term live-cell imaging of single Arabidopsis cells undergoing proto-xylem trans-differentiation, resulting in spiral wall patterns, to understand microtubule re-organization. By combining simulations and live-cell imaging we further explain how the xylem walldeficient and microtubule-severing KATANIN contributes to microtubule and wall patterning. By combining quantitative microscopy and modelling we devise a framework to understand how microtubule re-organization supports wall patterning. Xylem cells subsequently undergo programmed cell death, which leads to the clearing of their cytoplasmic content and the resulting formation of a hollow tube that provides the water-conducting capacity of vascular plants. Besides the phenolic compound lignin, which renders secondary walls strong and waterproof, the major load-bearing component of plant cell walls is cellulose; a β-1,4-linked glucan. The CSC delivery to, and locomotion within, the plasma membrane is guided by cortical microtubules that presumably are associated with the plasma membrane and by cellulose microfibrils when CSCs temporarily lost microtubule guidance

Methods

Results

Conclusion