Genome-Wide Identification of Two-Component System Genes in Cucurbitaceae Crops and Expression Profiling Analyses in Cucumber.

Yanjun He,Li Qin,Gang Lu,Tao Zou,Lifei Chen,Xue Liu,Changtian Pan

doi:10.3389/fpls.2016.00899

Abstract

Cucumber and watermelon, which belong to Cucurbitaceae family, are economically important cultivated crops worldwide. However, these crops are vulnerable to various adverse environments. Two-component system (TCS), consisting of histidine kinases (HKs), phosphotransfers (HPs), and response regulator proteins (RRs), plays important roles in various plant developmental processes and signaling transduction in responses to a wide range of biotic and abiotic stresses. No systematic investigation has been conducted on TCS genes in Cucurbitaceae species. Based on the completion of the cucumber and watermelon genome draft, we identified 46 and 49 TCS genes in cucumber and watermelon, respectively. The cucumber TCS members included 18 HK(L)s, 7 HPs, and 21 RRs, whereas the watermelon TCS system consisted of 19 HK(L)s, 6 HPs, and 24 RRs. The sequences and domains of TCS members from these two species were highly conserved. Gene duplication events occurred rarely, which might have resulted from the absence of recent whole-genome duplication event in these two Cucurbitaceae crops. Numerous stress- and hormone-responsive cis-elements were detected in the putative promoter regions of the cucumber TCS genes. Meanwhile, quantitative real-time PCR indicated that most of the TCS genes in cucumber were specifically or preferentially expressed in certain tissues or organs, especially in the early developing fruit. Some TCS genes exhibited diverse patterns of gene expression in response to abiotic stresses as well as exogenous trans-zeatin (ZT) and abscisic acid (ABA) treatment, suggesting that TCS genes might play significant roles in responses to various abiotic stresses and hormones in Cucurbitaceae crops.

Highlights

Protein phosphorylation is a key mechanism for regulating signal transduction in eukaryotes and prokaryotes
BLASTP searches were performed in Cucurbit Genomics Database to explore the putative Two-component system (TCS) in cucumber and watermelon by using 280 TCS protein sequences as queries from Arabidopsis, rice, maize, soybean, wheat, and Chinese cabbage
46 TCS members consisting of 18 histidine kinases (HKs)(L)s, 7 histidine-containing phosphotransfers (HPs), and 21 regulator proteins (RRs) were identified in cucumber (Table S1)

Summary

Introduction

Protein phosphorylation is a key mechanism for regulating signal transduction in eukaryotes and prokaryotes. Plant TCS components typically consist of three signal transducers, namely hybrid HKs with both a His-kinase (HK) domain and a receiver (Rec) domain, histidine-containing phosphotransfers (HPs), and RRs. HP is regarded as a medium for the transfer of the phosphoryl group between the HK and the RR (Urao et al, 2000; Hwang et al, 2002; Schaller et al, 2008). TCS signal transduction mechanism was deeply investigated in plant cytokinin signaling (Hwang et al, 2002; Grefen and Harter, 2004). In Arabidopsis, AHK2, AHK3, and AHK4 function as cytokinin receptors and respond to stress negatively in cytokinin signal via TCS These cytokinin receptors perceived cytokinin and were autophosphorylated. TypeB ARRs could bind to multiple cis-elements in the promoter of target genes, such as MAPKs and other stress-related genes, to participate in stress responses (Wurgler-Murphy and Saito, 1997; Hwang et al, 2002; Grefen and Harter, 2004)

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Results

Conclusion