Establishment of a Live-Imaging Analysis for Polarized Growth of Conchocelis in the Multicellular Red Alga Neopyropia yezoensis

Yuji Hiwatashi,Nagisa Takada,Koji Mikami,Mizuho Shimada

doi:10.3389/fpls.2021.716011

Abstract

A wide range of tip-growing cells in plants display polarized cell growth, which is an essential cellular process for the form and function of individual cells. Understanding of the regulatory mechanisms underlying tip growth in terrestrial plants has improved. Cellular processes involved in tip growth have also been investigated in some algae species that form filamentous cells, but their regulatory mechanisms remain unclear. In the macro red alga Neopyropia yezoensis, for which genome information has recently been released, the conchocelis apical cell exhibits tip growth and forms a filamentous structure. Here, we report a live-imaging technique using high-resolution microscopy to analyze the tip growth and cell division of N. yezoensis conchocelis. This imaging analysis addressed tip growth dynamics and cell division in conchocelis apical cells. The directionality and tip growth expansion were disrupted by the application of cytoskeletal drugs, suggesting the involvement of microtubules (MTs) and actin filaments (AFs) in these processes. A growing apical cell mostly contained a single chloroplast that moved toward the expanding part of the apical cell. Drug application also inhibited chloroplast movement, implying that the movement may be dependent on the cytoskeleton. The study determined that live-imaging analysis is a versatile approach for exploring the dynamics of tip growth and cell division in N. yezoensis conchocelis, which provides insights into the regulatory mechanisms underlying cellular growth in multicellular red algae.

Highlights

A wide variety of tip-growing cells in fungi, animals, and plants exhibit polarized cell growth, which is a cellular process essential for the formation and function of the individual cell
We routinely used the medium with 0.2% Noriseed for live imaging because conchocelis cells were occasionally discolored in the medium supplemented with 0.1% Noriseed, when the conchocelis cells were cultured for 2 weeks (Supplementary Figure 1)
Time-lapse imaging analysis addressed the dynamics of polarized expansion at the tips of the apical dome in conchocelis apical cells

Summary

Introduction

A wide variety of tip-growing cells in fungi, animals, and plants exhibit polarized cell growth, which is a cellular process essential for the formation and function of the individual cell. Coupled with turgor pressure-driven cell expansion, that leads to restricted growth in this limited zone. The relationship between the cytoskeleton, anisotropic deposition of the cell wall, and polar exocytosis has been a subject of much interest in model plants, such as the eudicot Arabidopsis thaliana and the moss Physcomitrium patens (Rounds and Bezanilla, 2013; Bascom et al, 2018). Movement of nuclei and chloroplasts, as well as cytoskeletal dynamics, has already been observed in tip-growing living cells using fluorescent microscopy techniques in these organisms. This approach is a powerful tool for studying intracellular organellar movement and cytoskeletal dynamics in tip-growing cells (Rounds and Bezanilla, 2013)

Methods

Results

Conclusion