Expression Patterns and Identified Protein-Protein Interactions Suggest That Cassava CBL-CIPK Signal Networks Function in Responses to Abiotic Stresses.

Yang Zhou,Xingyu Jiang,Youquan Xia,Chunyan Mo,Ning Ren,Shumin Wan

doi:10.3389/fpls.2018.00269

Abstract

Cassava is an energy crop that is tolerant of multiple abiotic stresses. It has been reported that the interaction between Calcineurin B-like (CBL) protein and CBL-interacting protein kinase (CIPK) is implicated in plant development and responses to various stresses. However, little is known about their functions in cassava. Herein, 8 CBL (MeCBL) and 26 CIPK (MeCIPK) genes were isolated from cassava by genome searching and cloning of cDNA sequences of Arabidopsis CBLs and CIPKs. Reverse-transcriptase polymerase chain reaction (RT-PCR) analysis showed that the expression levels of MeCBL and MeCIPK genes were different in different tissues throughout the life cycle. The expression patterns of 7 CBL and 26 CIPK genes in response to NaCl, PEG, heat and cold stresses were analyzed by quantitative real-time PCR (qRT-PCR), and it was found that the expression of each was induced by multiple stimuli. Furthermore, we found that many pairs of CBLs and CIPKs could interact with each other via investigating the interactions between 8 CBL and 25 CIPK proteins using a yeast two-hybrid system. Yeast cells co-transformed with cassava MeCIPK24, MeCBL10, and Na+/H+ antiporter MeSOS1 genes exhibited higher salt tolerance compared to those with one or two genes. These results suggest that the cassava CBL-CIPK signal network might play key roles in response to abiotic stresses.

Highlights

Calcium is used by most cells to convert external signals into cytosolic information, which can drive processes that are required for full responses to a particular stimulus (Zhai et al, 2013)
In order to identify the calcineurin B-like proteins (CBL) and CBL-interacting protein kinase (CIPK) genes from cassava, 10 CBL and 26 CIPK protein sequences from Arabidopsis were used as queries to run BLAST searches using the cassava genomic DNA database
The results indicate that the sequences of MeCBLs are highly conserved: all the MeCBLs containing four EF hand motifs, which are similar to the AtCBLs EF-hand motifs

Summary

Introduction

Calcium is used by most cells to convert external signals into cytosolic information, which can drive processes that are required for full responses to a particular stimulus (Zhai et al, 2013). Elevation of the cytosolic calcium concentration is a primary event in the responses to many environmental stresses, such as high salinity, drought and cold (Ma et al, 2010). Transient Ca2+ change may be sensed by several Ca2+-binding proteins including calmodulin (CaM), Ca2+-dependent protein kinases (CDPKs) and calcineurin B-like proteins (CBL) (Luan et al, 2002). Such calcium-binding proteins likely function as sensors that recognize changes in calcium parameters and relay these signals into downstream responses, such as phosphorylation cascades and regulation of gene expression (Sanders et al, 2002; Luan et al, 2009).

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Conclusion