A Role for Barley Calcium-Dependent Protein Kinase CPK2a in the Response to Drought

Abstract

Increasing the drought tolerance of crops is one of the most challenging goals in plant breeding. To improve crop productivity during periods of water deficit, it is essential to understand the complex regulatory pathways that adapt plant metabolism to environmental conditions. Among various plant hormones and second messengers, calcium ions are known to be involved in drought stress perception and signaling. Plants have developed specific calcium-dependent protein kinases that convert calcium signals into phosphorylation events. In this study we attempted to elucidate the role of a calcium-dependent protein kinase in the drought stress response of barley (Hordeum vulgare L.), one of the most economically important crops worldwide. The ongoing barley genome project has provided useful information about genes potentially involved in the drought stress response, but information on the role of calcium-dependent kinases is still limited. We found that the gene encoding the calcium-dependent protein kinase HvCPK2a was significantly upregulated in response to drought. To better understand the role of HvCPK2a in drought stress signaling, we generated transgenic Arabidopsis plants that overexpressed the corresponding coding sequence. Overexpressing lines displayed drought sensitivity, reduced nitrogen balance index (NBI), an increase in total chlorophyll content and decreased relative water content. In addition, in vitro kinase assay experiments combined with mass spectrometry allowed HvCPK2a autophosphorylation sites to be identified. Our results suggest that HvCPK2a is a dual-specificity calcium-dependent protein kinase that functions as a negative regulator of the drought stress response in barley.

Genome-Wide Association Study of Salinity Tolerance During Germination in Barley (Hordeum vulgare L.)

“…When barley and rice roots were colonized by endophytic basidiomycete fungi (P. indica), the host plants enhanced performance under salinity stress (Baltruschat et al, 2008;Vahabi et al, 2016;Jogawat et al, 2016). The protein kinase superfamily is another important gene family that has been characterized in several plants; e.g., for drought tolerance in barley (Cieśla et al, 2016;Yang et al, 2017) and salinity stress tolerance in wheatgrass (Shen et al, 2001). Protein kinase gene family, regulated by transcription factors (TFs) and microRNAs (miRNAs), plays key roles in salt stress tolerance in cotton (Shehzad et al, 2019).…”

Identification of Differentially Expressed Drought-Responsive Genes in Guar [Cyamopsis tetragonoloba (L.) Taub]

“…A positive regulatory effect of CDPKs in drought stress signaling was explained by the improved expression of ABA-responsive genes [72]. Ciesla et al [73] reported that the gene encoding the calciumdependent protein kinase HvCPK2a was significantly upregulated in barley (Hordeum vulgare L.) in response to drought. The CBL-interacting protein kinase 16 gene was differentially expressed in three barley genotypes throughout the reproductive stage under drought stress [74].…”

Functional characterization and regulatory mechanism of wheat CPK34 kinase in response to drought stress

“…ABA is the most critical phytohormone in plant drought stress responses, and several plant CPKs are involved in the mechanisms of drought stress response through an ABA-dependent manner [43]. The Arabidopsis plants overexpressing VaCPK20 gene showed increased drought tolerance, and enhanced the transcripts of COR47, NHX1, KIN1, and ABF3 genes, which were induced by ABA and drought stresses [44].…”