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Open Access Research article

Identification, expression and interaction analyses of calcium-dependent protein kinase (CPK) genes in canola (Brassica napus L.)

Hanfeng Zhang1, Wu-Zhen Liu1, Yupeng Zhang1, Min Deng1, Fangfang Niu1, Bo Yang1*, Xiaoling Wang1, Boya Wang1, Wanwan Liang1, Michael K Deyholos2 and Yuan-Qing Jiang1*

Author Affiliations

1 State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest A & F University, Yangling, Shaanxi 712100, China

2 Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada

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BMC Genomics 2014, 15:211  doi:10.1186/1471-2164-15-211

Published: 19 March 2014

Abstract

Background

Canola (Brassica napus L.) is one of the most important oil-producing crops in China and worldwide. The yield and quality of canola is frequently threatened by environmental stresses including drought, cold and high salinity. Calcium is a well-known ubiquitous intracellular secondary messenger in plants. Calcium-dependent protein kinases (CPKs) are Ser/Thr protein kinases found only in plants and some protozoans. CPKs are Ca2+ sensors that have both Ca2+ sensing function and kinase activity within a single protein and play crucial roles in plant development and responses to various environmental stresses.

Results

In this study, we mined the available expressed sequence tags (ESTs) of B. napus and identified a total of 25 CPK genes, among which cDNA sequences of 23 genes were successfully cloned from a double haploid cultivar of canola. Phylogenetic analysis demonstrated that they could be clustered into four subgroups. The subcellular localization of five selected BnaCPKs was determined using green fluorescence protein (GFP) as the reporter. Furthermore, the expression levels of 21 BnaCPK genes in response to salt, drought, cold, heat, abscisic acid (ABA), low potassium (LK) and oxidative stress were studied by quantitative RT-PCR and were found to respond to multiple stimuli, suggesting that canola CPKs may be convergence points of different signaling pathways. We also identified and cloned five and eight Clade A basic leucine zipper (bZIP) and protein phosphatase type 2C (PP2C) genes from canola and, using yeast two-hybrid and bimolecular fluorescence complementation (BiFC), determined the interaction between individual BnaCPKs and BnabZIPs or BnaPP2Cs (Clade A). We identified novel, interesting interaction partners for some of the BnaCPK proteins.

Conclusion

We present the sequences and characterization of CPK gene family members in canola for the first time. This work provides a foundation for further crop improvement and improved understanding of signal transduction in plants.

Keywords:
Abiotic stress; Basic leucine zipper transcription factor; Brassica napus; Calcium-dependent protein kinase; Protein phosphatase 2C