Stomatal Closure and Rise in ROS/NO of Arabidopsis Guard Cells by Tobacco Microbial Elicitors: Cryptogein and Harpin.

Gunja Gayatri,Agepati S Raghavendra,Srinivas Agurla,Kazuyuki Kuchitsu,Appa R Podile,Kondreddy Anil

doi:10.3389/fpls.2017.01096

Gunja Gayatri, Agepati S Raghavendra + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2017.01096

Copy DOI

Abstract

Plants use stomatal closure mediated by elicitors as the first step of the innate immune response to restrict the microbial entry. We present a comprehensive study of the effect of cryptogein and harpin, two elicitors from microbial pathogens of tobacco, on stomatal closure and guard cell signaling components in Arabidopsis thaliana, a model plant. Cryptogein as well as harpin induced stomatal closure, while elevating the levels of reactive oxygen species (ROS) and nitric oxide (NO) in the guard cells of A. thaliana. Kinetic studies with fluorescent dyes revealed that the rise in ROS levels preceded that of NO in guard cells, when treated with these two elicitors. The restriction of NO levels in guard cells, even by ROS modulators indicates the essentiality of ROS for NO production during elicitor-triggered stomatal closure. The signaling events during elicitor-induced stomatal closure appear to converge at NADPH oxidase and ROS production. Our results provide the first report on stomatal closure associated with rise in ROS/NO of guard cells by cryptogein and harpin in A. thaliana. Our results establish that A. thaliana can be used to study stomatal responses to the typical elicitors from microbial pathogens of other plants. The suitability of Arabidopsis opens up an excellent scope for further studies on signaling events leading to stomatal closure by microbial elicitors.

Highlights

Stomata, the microscopic pores on the epidermis are the gateways for CO2 and H2O (Hetherington and Woodward, 2003) and for microbes (Agurla et al, 2014)
We extended our studies to evaluate the responses of stomatal guard cells in mutants of A. thaliana deficient in signaling components involved in reactive oxygen species (ROS)/nitric oxide (NO) production
The levels of ROS or NO in guard cells were monitored by using fluorescent probes of CM-H2DCFDA and DAF-FM 4-amino-5-methyl amino-2 (DA), respectively

Summary

Introduction

The microscopic pores on the epidermis are the gateways for CO2 and H2O (Hetherington and Woodward, 2003) and for microbes (Agurla et al, 2014). Several signaling components, are involved in ABA-induced stomatal closure such as PYR/RCAR-PP2CSnRK2 complexes, G-proteins, phospholipids, OST1, free Ca2+ and cation/anion channels (Hubbard et al, 2010; Raghavendra et al, 2010; Lee and Luan, 2012; Zhu et al, 2012; Murata et al, 2015) The transduction of both biotic and abiotic signals appears to share some common signaling components in guard cells, such as ROS and NO (Melotto et al, 2006; Srivastava et al, 2009; Khokon et al, 2010a,b; Zeng et al, 2010; Zhang et al, 2012; Agurla et al, 2014)

Methods

Results

Discussion

Conclusion