Revealing the Role of the Calcineurin B-Like Protein-Interacting Protein Kinase 9 (CIPK9) in Rice Adaptive Responses to Salinity, Osmotic Stress, and K+ Deficiency.

Sergey Shabala,Meixue Zhou,Lana Shabala,Min Yu,Gayatri Venkataraman,Zhong-Hua Chen,Jayakumar Bose,Mohammad Alnayef

doi:10.3390/plants10081513

Abstract

In plants, calcineurin B-like (CBL) proteins and their interacting protein kinases (CIPK) form functional complexes that transduce downstream signals to membrane effectors assisting in their adaptation to adverse environmental conditions. This study addresses the issue of the physiological role of CIPK9 in adaptive responses to salinity, osmotic stress, and K+ deficiency in rice plants. Whole-plant physiological studies revealed that Oscipk9 rice mutant lacks a functional CIPK9 gene and displayed a mildly stronger phenotype, both under saline and osmotic stress conditions. The reported difference was attributed to the ability of Oscipk9 to maintain significantly higher stomatal conductance (thus, a greater carbon gain). Oscipk9 plants contained much less K+ in their tissues, implying the role of CIPK9 in K+ acquisition and homeostasis in rice. Oscipk9 roots also showed hypersensitivity to ROS under conditions of low K+ availability suggesting an important role of H2O2 signalling as a component of plant adaptive responses to a low-K environment. The likely mechanistic basis of above physiological responses is discussed.

Highlights

An understanding of plant responses to abiotic stress is vital for the genetic engineering of climate-resilient crops
More severe (80 mM) salinity treatment caused a further reduction in plant dry weight (DW) that was more pronounced in the Oscipk9 mutant
The osmolality was significantly (p ≤ 0.01) lower in the Oscipk9 mutant compared to the wild type (WT) (Figure 1D)

Summary

Introduction

An understanding of plant responses to abiotic stress is vital for the genetic engineering of climate-resilient crops. This involves understanding the mechanisms by which plants sense stresses and generate appropriate stress-induced signals, such as changes in the cytosolic free Ca2+ and ROS [1,2,3]. Salinity [7,8,9], drought [10,11], and K+ deficiency [12] have all been shown to induce transient Ca2+ influx, thereby increasing cytosolic Ca2+ concentration This change in the cytosolic Ca2+ levels can be detected by numerous high-affinity calcium sensors. Several families of Ca2+ sensors have been recognised, including calmodulin (CaM) and CaM-related proteins [13,14], Ca2+ dependent protein kinases (CDPKs) [15,16], and calcineurin B-like (CBL) proteins and their interacting protein kinases (CIPKs) [17]

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Conclusion