Arabidopsis KASH Proteins SINE1 and SINE2 Are Involved in Microtubule Reorganization During ABA-Induced Stomatal Closure.

Alecia Biel,Iris Meier,Morgan Moser

doi:10.3389/fpls.2020.575573

Abstract

Abscisic acid (ABA) induces stomatal closure by utilizing complex signaling mechanisms, allowing for sessile plants to respond rapidly to ever-changing environmental conditions. ABA regulates the activity of plasma membrane ion channels and calcium-dependent protein kinases, Ca2+ oscillations, and reactive oxygen species (ROS) concentrations. Throughout ABA-induced stomatal closure, the cytoskeleton undergoes dramatic changes that appear important for efficient closure. However, the precise role of this cytoskeletal reorganization in stomatal closure and the nature of its regulation are unknown. We have recently shown that the plant KASH proteins SINE1 and SINE2 are connected to actin organization during ABA-induced stomatal closure but their role in microtubule (MT) organization remains to be investigated. We show here that depolymerizing MTs using oryzalin can restore ABA-induced stomatal closure deficits in sine1-1 and sine2-1 mutants. GFP-MAP4-visualized MT organization is compromised in sine1-1 and sine2-1 mutants during ABA-induced stomatal closure. Loss of SINE1 or SINE2 results in loss of radially organized MT patterning in open guard cells, aberrant MT organization during stomatal closure, and an overall decrease in the number of MT filaments or bundles. Thus, SINE1 and SINE2 are necessary for establishing MT patterning and mediating changes in MT rearrangement, which is required for ABA-induced stomatal closure.

Highlights

Stomata open and close to regulate gas exchange between the plant and its environment
Oryzalin did not induce stomatal closure in sine1-1 and sine2-1, closure comparable to WT was seen in the mutants in the presence of oryzalin and abscisic acid (ABA)
We have previously reported that SINE1 and SINE2 play a role in stomatal dynamics in response to light, dark, and ABA, but not the bacterial elicitor flg22 (Biel et al, 2020)

Summary

Introduction

Stomata open and close to regulate gas exchange between the plant and its environment. These stomatal dynamics are controlled by a variety of environmental factors, including biotic and abiotic stresses. We have shown previously that in Arabidopsis SUN-interacting nuclear envelope protein 1 and 2 (SINE1 and SINE2), components of a plant Linker of Nucleoskeleton and Cytoskeleton (LINC). Arabidopsis KASH Proteins and Microtubule Organization complex, play a role in stomatal opening and closing (Biel et al, 2020). SINE1 and SINE2 are plant KASH proteins, which bind to Arabidopsis SUN1 and SUN2 (Zhou et al, 2014). The ABA-induced stomatal closure phenotype is, in part, attributed to impairments in Ca2+ and F-actin regulation (Biel et al, 2020)

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Results

Conclusion