Calcium-Dependent Protein Kinase in Ginger Binds with Importin-α through Its Junction Domain for Nuclear Localization, and Further Interacts with NAC Transcription Factor

Abstract

Calcium-dependent protein kinases (CDPKs) are important sensors of Ca2+ elevations in plant cells regulating the gene expression linked with various cellular processes like stress response, growth and development, metabolism, and cytoskeleton dynamics. Ginger is an extensively used spice due to its unique flavor and immense medicinal value. The two major threats that interfere with the large scale production of ginger are the salinity and drought stress. ZoCDPK1 (Zingiber officinale Calcium-dependent protein kinase 1) is a salinity and drought-inducible CDPK gene isolated from ginger and undergoes dynamic subcellular localization during stress conditions. ZoCDPK1, with signature features of a typical Ca2+ regulated kinase, also possesses a bipartite nuclear localization sequence (NLS) in its junction domain (JD). A striking feature in ZoCDPK1 is the rare occurrence of a coupling between the NLS in JD and consensus sequences in regulatory domain. Here, we further identified its nature of nuclear localization and its interaction partners. In the homology model generated for ZoCDPK1, the regulatory domain mimics the crystal structure of the regulatory domain in Arabidopsis CDPK1. Molecular docking simulation of importin (ZoIMPα), an important protein involved in nuclear translocation, into the NLS of ZoCDPK1 was well-visualized. Furthermore, the direct interaction of ZoCDPK1 and ZoIMPα proteins was studied by the yeast 2-hybrid (Y2H) system, which confirmed that junction domain (JD) is an important interaction module required for ZoCDPK1 and ZoIMPα binding. The probable interacting partners of ZoCDPK1 were also identified using Y2H experiment. Of the 10 different stress-related interacting partners identified for ZoCDPK1, NAC transcription factor (TF) needs special mention, especially in the context of ZoCDPK1 function. The interaction between ZoCDPK1 and NAC TF, in fact, corroborate with the results of gene expression and over-expression studies of ZoCDPK1. Hence ZoCDPK1 is operating through NAC TF mediated ABA-independent, cold non-responsive stress signaling pathway in ginger.

Molecular Characterization Reveals the Involvement of Calcium Dependent Protein Kinases in Abiotic Stress Signaling and Development in Chickpea (Cicer arietinum)

“…Thus, the presence of important characteristic domains and motifs in all the CaCDPK proteins confirms their authenticity and integrity. Similar features of the 3-D structure of CDPK proteins were obtained in different plant species including Arabidopsis , rice, maize, ginger ( Zingiber officinale ), and sorghum (Mittal et al, 2017 ; Vivek et al, 2017 ). Suggesting that the CDPK protein structure is highly conserved, with similar structural folds and conformational arrangements in higher plants.…”

Revisiting the Role of Plant Transcription Factors in the Battle against Abiotic Stress

“…Functional modulation of transcription factors via interactions with regulatory proteins is an important step in the regulation of signal transduction pathways [ 216 , 217 ]. Recently, several research studies have established that interactions between TFs with their interacting partners (proteins) have a significant role in mediating abiotic stress tolerance in plants [ 218 , 219 ]. For example, in chickpea, two putative transcription factors, Myb.Ph and Athb-1, bind to the promoter of a stress-responsive ferritin protein, CaFer1; in addition, CaFer1 interacts with iron transporter IRT1, and the resulting ferritin1-complex then mediates iron homeostasis and drought stress tolerance [ 218 ].…”

“…In rice, interaction of MODD (Mediator of OsbZIP46 deactivation and degradation, a homolog of AFP) protein with OsbZIP46 through the D domain upsets the regulation of ABA signaling and drought tolerance [ 225 ]. Using the Y2H system, Vivek et al [ 219 ] identified NAC TF as an interacting partner of ZoCDPK1 ( Zingiber officinale Calcium-dependent protein kinase 1) and showed that ZoCDPK1 operates in ginger through NAC-mediated, ABA-independent, cold nonresponsive stress signaling pathway. Similarly, the physical interaction of late embryogenesis abundant (LEA) protein, GmLEA3.1, with soybean GmDi19-5, a member of zinc finger TF family, enhances the stability of the GmDi19-5 protein and promotes abiotic stress sensitivity in transgenic Arabidopsis lines [ 226 ].…”

Genome-wide identification and functional characterization of CDPK gene family reveal their involvement in response to drought stress in Gossypium barbadense

“…Overexpression of OsCDPK9 play an active role in drought stress tolerance ( Wei et al, 2014 ). Overexpression of tobacco ZoCDPK1 gene can affect salt and drought stress ( Vivek et al, 2017 ). Overexpression of ZmCPK4 in the transgenic Arabidopsis enhanced drought stress tolerance ( Jiang et al, 2013 ).…”