Salt stress response triggers activation of the jasmonate signaling pathway leading to inhibition of cell elongation in Arabidopsis primary root.

Camilo E Valenzuela,Giovanna S Miranda,Orlando Acevedo-Acevedo,Carlos R Figueroa,Loreto Holuigue,Pablo M Figueroa,Pablo Vergara-Barros

doi:10.1093/jxb/erw202

Abstract

Salinity is a severe abiotic stress that affects irrigated croplands. Jasmonate (JA) is an essential hormone involved in plant defense against herbivory and in responses to abiotic stress. However, the relationship between the salt stress response and the JA pathway in Arabidopsis thaliana is not well understood at molecular and cellular levels. In this work we investigated the activation of JA signaling by NaCl and its effect on primary root growth. We found that JA-responsive JAZ genes were up-regulated by salt stress in a COI1-dependent manner in the roots. Using a JA-Ile sensor we demonstrated that activation of JA signaling by salt stress occurs in the meristematic zone and stele of the differentiation zone and that this activation was dependent on JAR1 and proteasome functions. Another finding is that the elongation zone (EZ) and its cortical cells were significantly longer in JA-related mutants (AOS, COI1, JAZ3 and MYC2/3/4 genes) compared with wild-type plants under salt stress, revealing the participation of the canonical JA signaling pathway. Noteworthy, osmotic stress - a component of salt stress - inhibited cell elongation in the EZ in a COI1-dependent manner. We propose that salt stress triggers activation of the JA signaling pathway followed by inhibition of cell elongation in the EZ. We have shown that salt-inhibited root growth partially involves the jasmonate signaling pathway in Arabidopsis.

Highlights

Soil salinity, the build-up of salts at or near the surface of the soil, is a widespread agricultural problem affecting the world’s irrigated cropland (Yamaguchi-Shinozaki and Shinozaki, 2006)
This result is consistent with variations in coronatine insensitive 1 (COI1) expression during the salt stress response do not play a major role in the up-regulation of JASMONATE ZIM-DOMAIN (JAZ) in the roots by salt treatment
Previous large-scale expression studies showed that some genes implicated in JA biosynthesis were induced in the roots by salt stress, suggesting that the biosynthesis of this hormone is induced in roots by salt stress (Jiang and Deyholos, 2006; Ma et al, 2006; Kilian et al, 2007)

Summary

Introduction

The build-up of salts at or near the surface of the soil, is a widespread agricultural problem affecting the world’s irrigated cropland (Yamaguchi-Shinozaki and Shinozaki, 2006). The SCFCOI1 complex is involved in the ubiquitin-dependent degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins in the presence of the biologically active JA-Ile (Chini et al, 2007; Thines et al, 2007; Yan et al, 2007; Fonseca et al, 2009). JAZ proteins bind to bHLH transcription factors (e.g. MYC2, MYC3, MYC4 and MYC5) that are activators of JA responses repressing their transcriptional activity and turning off the expression of the early JA-responsive genes (Chini et al, 2007; Cheng et al, 2011; Fernández-Calvo et al, 2011; Niu et al, 2011; Figueroa and Browse, 2012, 2015; Qi et al, 2015; Zhang et al, 2015). After JA responses are switched on, hormone signaling is attenuated by induction of the JA-responsive JAZ genes in order to avoid the inhibitory effect that over-activation of JA responses has on plant growth (Chini et al, 2007; Thines et al, 2007; Chung et al, 2008; Zhang and Turner, 2008)

Methods

Results

Conclusion