Putative role of glutamine in the activation of CBL/CIPK signalling pathways during salt stress in sorghum

Abstract

The salt overly sensitive (SOS) pathway is the only mechanism known for Na extrusion in plant cells. SOS pathway activation involves Ca-sensing proteins, such as calcineurin B-like (CBL) proteins, and CBL-interacting protein kinases (CIPKs). In this signalling mechanism, a transit increase in cytosolic Ca concentration triggered by Na accumulation is perceived by CBL (also known as SOS3). Afterward, SOS3 physically interacts with a CIPK (also known as SOS2), forming the SOS2/SOS3 complex, which can regulate the number downstream targets, controlling ionic homeostasis. For instance, the SOS2/SOS3 complex phosphorylates and activates the SOS1 plasmalemma protein, which is a Na/H antiporter that extrudes Na out of the cell. The CBL-CIPK networking system displays specificity, complexity and diversity, constituting a critical response against salt stress and other abiotic stresses. In a study reported in the journal Plant and Cell Physiology, we showed that NH induces the robust activation of transporters for Na homeostasis in root cells, especially the SOS1 antiporter and plasma membrane H-ATPase, differently than does NO. Despite some studies having shown that external NH ameliorates salt-induced effects on ionic homeostasis, there is no evidence that NH per se or some product of its assimilation is responsible for these responses. Here, we speculate about the signalling role behind glutamine in CBL-CIPK modulation, which could effectively activate the SOS pathway in NH-fed stressed plants.

Overexpression of a Novel ROP Gene from the Banana (MaROP5g) Confers Increased Salt Stress Tolerance

“…To gain an in-depth understanding of MaROP5g function in response to salt stress, we measured the expression of three Salt Overly Sensitive (SOS)-pathway genes (namely SOS1 , SOS2 , and SOS3 ) and several genes encoding calcium-signaling pathway proteins, including calcineurin B-like (CBL) proteins, CBL-interacting protein kinases (CIPKs), and calcium-dependent protein kinases (CDPKs) [ 39 ], in both WT and MaROP5g -overexpressing A. thaliana ( Figure 7 ). Under standard growth conditions, we observed no significant differences in the transcription levels of the tested genes in the transgenic lines as compared to those in WT plants.…”

“…Many different ion transporters and channel proteins, such as SOS, CDPK, CBL, and CIPK, play crucial roles in maintaining ion homeostasis during salt stress [ 39 , 42 , 43 ]. For example, under salt stress, the SOS1 and SOS2 proteins regulate Na + /K + homeostasis in A. thaliana ; once the calcium binding protein SOS3 senses an increase in cytosolic calcium concentration, the SOS3–SOS2 protein kinase complex activates the SOS1 ion transporter [ 42 , 43 ].…”

“…For example, under salt stress, the SOS1 and SOS2 proteins regulate Na + /K + homeostasis in A. thaliana ; once the calcium binding protein SOS3 senses an increase in cytosolic calcium concentration, the SOS3–SOS2 protein kinase complex activates the SOS1 ion transporter [ 42 , 43 ]. In addition, calcium (Ca 2+ ), as a second messenger, plays an important role in salt stress processes [ 39 , 44 ]. Ca 2+ increase can be decoded and recognized by Ca 2+ sensors, including CBLs, CIPKs, and CDPKs [ 44 ].…”

“…Ca 2+ increase can be decoded and recognized by Ca 2+ sensors, including CBLs, CIPKs, and CDPKs [ 44 ]. CBLs recognize the increase in cytosolic Ca 2+ concentration triggered by Na + accumulation [ 39 ]. CIPKs and CDPKs may unify and coordinate ionic homeostasis at the cellular and organismal level [ 44 ].…”

Comprehensive Effect of Salt Stress and Peanut Cultivars on the Bacterial Community Structure and Diversity of Peanut Rhizosphere Soils

“…7A). Amino acids such as glutamine and proline can improve salt tolerance in plants [33,34], and some chaperones, such as heat shock proteins, are also identi ed as stress tolerance enhancers for plants [23]. Moreover, inorganic ion transport and metabolism is high.…”