Expression, Subcellular Localization, and Interactions of CPK Family Genes in Maize.

Muhammad Hayder Bin Khalid,Wan Chen Li,Hao Qiang Yu,Jing Tao Qu,Muhammad Ali Raza,Ling Yang Feng,Imran Khan,Fu Ai Sun,Feng Ling Fu

doi:10.3390/ijms20246173

Muhammad Hayder Bin Khalid, Wan Chen Li + Show 7 more

Open Access

https://doi.org/10.3390/ijms20246173

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Abstract

Calcium-dependent protein kinase (CPKs) is a key player in the calcium signaling pathway to decode calcium signals into various physiological responses. cDNA sequences of 9 ZmCPK genes were successfully cloned from all four phylogenetic groups in maize. qRT-PCR analysis showed the expression variation of these selected genes under abscisic acid (ABA) and calcium chloride (CaCl2) treatment. Due to the presence of N-myristoylation/palmitoylation sites, the selected ZmCPK members were localized in a plasma membrane. To clarify whether ZmCPK, a key player in calcium signaling, interacts with key players of ABA, protein phosphatase 2Cs (PP2Cs) and the SNF1-related protein kinase 2s (SnRK2s) and mitogen-activated protein kinase (MAPK) signaling pathways in maize, we examined the interaction between 9 CPKs, 8 PP2Cs, 5 SnRKs, and 20 members of the MPK family in maize by using yeast two-hybrid assay. Our results showed that three ZmCPKs interact with three different members of ZmSnRKs while four ZmCPK members had a positive interaction with 13 members of ZmMPKs in different combinations. These four ZmCPK proteins are from three different groups in maize. These findings of physical interactions between ZmCPKs, ZmSnRKs, and ZmMPKs suggested that these signaling pathways do not only have indirect influence but also have direct crosstalk that may involve the defense mechanism in maize. The present study may improve the understanding of signal transduction in plants.

Highlights

Plants suffer from various environmental stresses, including drought, high salinity, and extreme temperatures [1,2,3]
The mutants of CPK1 and CPK1a inhibited the activity of protein phosphatases type 2Cs (PP2C), which is capable of blocking the responses to Abscisic acid (ABA) in Arabidopsis [21]
The expression patterns of the nine ZmCPKs were detected by qRT-PCR, and the results showed variations under ABA and CaCl2 as calcium treatments

Summary

Introduction

Plants suffer from various environmental stresses, including drought, high salinity, and extreme temperatures [1,2,3]. Genetics and biochemical studies have shown that CPKs are the key players in biological processes and plant signaling pathways, including innate immunity, oxidative burst, abiotic stress responses, and hormone signaling [7,8,9,10,11,12,13,14,15]. The mutants of CPK1 and CPK1a inhibited the activity of protein phosphatases type 2Cs (PP2C), which is capable of blocking the responses to ABA in Arabidopsis [21]. All this evidence suggests that CPK plays a critical role at the intersection of ABA and Ca2+ signaling pathways [31]. Phosphorylation of OsMPK5 by OsCPK18 proposed the direct crosstalk between CPK and MAPK signaling pathways [42]

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