The Role of Proteases in Determining Stomatal Development and Tuning Pore Aperture: A Review.

Dimitrios Fanourakis,Nikolaos Nikoloudakis,Georgios Doupis,Emmanouil Markakis,Polyxeni Pappi,Spyridoula N Charova,Georgios Tsaniklidis,Costas Delis

doi:10.3390/plants9030340

Abstract

Plant proteases, the proteolytic enzymes that catalyze protein breakdown and recycling, play an essential role in a variety of biological processes including stomatal development and distribution, as well as, systemic stress responses. In this review, we summarize what is known about the participation of proteases in both stomatal organogenesis and on the stomatal pore aperture tuning, with particular emphasis on their involvement in numerous signaling pathways triggered by abiotic and biotic stressors. There is a compelling body of evidence demonstrating that several proteases are directly or indirectly implicated in the process of stomatal development, affecting stomatal index, density, spacing, as well as, size. In addition, proteases are reported to be involved in a transient adjustment of stomatal aperture, thus orchestrating gas exchange. Consequently, the proteases-mediated regulation of stomatal movements considerably affects plants’ ability to cope not only with abiotic stressors, but also to perceive and respond to biotic stimuli. Even though the determining role of proteases on stomatal development and functioning is just beginning to unfold, our understanding of the underlying processes and cellular mechanisms still remains far from being completed.

Highlights

In all living cells, the breakdown of functional proteins, as well as, the recycling of non-functional, misfolded or obsolete polypeptides to amino acids, are fundamental regulatory physiological and developmental processes, involving a diverse array of enzymes
This review examines the involvement of specific classes of proteases in the regulatory and signaling pathways that govern stomatal development, as well as, stomatal pore aperture tuning
Wild-type Arabidopsis thaliana plants and the majority of plant species typically undergo a repression in stomatal development under elevated CO2 [41]

Summary

Introduction

The breakdown of functional proteins, as well as, the recycling of non-functional, misfolded or obsolete polypeptides to amino acids, are fundamental regulatory physiological and developmental processes, involving a diverse array of enzymes These enzymes either selectively terminate proteins or generate biologically active peptides via cleavage. After the initiation arethe structurally diverse enzymes despite having a common substrate-activity; namely they catalyze proteolytic mechanism, this process is mainly regulated by protease inhibitors [8]. Hormonal and environmental signals are proven to affect this process by and FAMA mechanism is achieved with an array of other proteins and transcriptional factors exhibiting targeting specific of the plethora of regulators that affect the SPCH, MUTE and FAMA mechanism complex interactions allowing for its fine tuning according to the external stimuli. This review examines the involvement of specific classes of proteases in the regulatory and signaling pathways that govern stomatal development, as well as, stomatal pore aperture tuning

Subtilisin-Like Serine Proteases

Papain-Like Cysteine Proteases

Aspartic Proteases

Conclusions and Perspectives