Guard Cell Microfilament Analyzer Facilitates the Analysis of the Organization and Dynamics of Actin Filaments in Arabidopsis Guard Cells.

Xin Li,Guanlin Chen,Shanjin Huang,Yanan Zhang,Naizhi Chen,Min Diao

doi:10.3390/ijms20112753

Abstract

The actin cytoskeleton is involved in regulating stomatal movement, which forms distinct actin arrays within guard cells of stomata with different apertures. How those actin arrays are formed and maintained remains largely unexplored. Elucidation of the dynamic behavior of differently oriented actin filaments in guard cells will enhance our understanding in this regard. Here, we initially developed a program called ‘guard cell microfilament analyzer’ (GCMA) that enables the selection of individual actin filaments and analysis of their orientations semiautomatically in guard cells. We next traced the dynamics of individual actin filaments and performed careful quantification in open and closed stomata. We found that de novo nucleation of actin filaments occurs at both dorsal and ventral sides of guard cells from open and closed stomata. Interestingly, most of the nucleated actin filaments elongate radially and longitudinally in open and closed stomata, respectively. Strikingly, radial filaments tend to form bundles whereas longitudinal filaments tend to be removed by severing and depolymerization in open stomata. By contrast, longitudinal filaments tend to form bundles that are severed less frequently in closed stomata. These observations provide insights into the formation and maintenance of distinct actin arrays in guard cells in stomata of different apertures.

Highlights

The size of stomatal pores, each surrounded by a pair of guard cells, regulates CO2 uptake and water loss, which is controlled by stomatal movement [1,2]
We performed careful characterization of the overall organization and dynamics of individual actin filaments within guard cells and found that actin filaments are arrayed into distinct structures within guard cells of stomata at different stages
We divided stomata into four distinct stages based on their apertures and found that actin filaments are arrayed into distinct structures within guard cells of stomata at different stages

Summary

Introduction

The size of stomatal pores, each surrounded by a pair of guard cells, regulates CO2 uptake and water loss, which is controlled by stomatal movement [1,2]. Given that guard cells have unique geometry and undergo changes during stomatal closure and opening, how to define the radial, longitudinal, and oblique orientation of individual actin filaments has not been solved clearly Using this approach, Shimono et al examined the behavior of actin filaments in guard cells in response to the activation of immune signaling and found that the purified pathogen elicitor flg (a highly conservative peptide of 22 amino acids in N terminus of bacteria flagellin) and chitin treatments induced some specific changes in actin configurations [9], but the underlying details of single filament dynamics remain unexplored. How these distinct actin arrays are constructed and maintained remains to be documented

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Discussion

Conclusion