Abstract
BackgroundChinese jujube (Ziziphus jujuba Mill.) is one of the most important members in the Rhamnaceae family. The whole genome sequence and more than 30,000 proteins of Chinese jujube have been obtained in 2014. Mitogen-activated protein kinase cascades are universal signal transduction modules in plants, which is rapidly activated under various biotic and abiotic stresses. To date, there has been no comprehensive analysis of the MAPK and MAPKK gene family in Chinese jujube at the whole genome level.ResultsBy performing a series of bioinformatics analysis, ten MAPK and five MAPKK genes were identified from the genome database of Chinese jujube, and then compared with the homologous genes from Arabidopsis. Phylogenetic analysis showed that ZjMAPKs was classified into four known groups, including A, B, C and D. ZjMAPKs contains five members of the TEY phosphorylation site and five members with the TDY motif. The ZjMAPKK family was subsequently divided into three groups, A, B and D. The gene structure, conserved motifs, functional annotation and chromosome distribution of ZjMAPKs and ZjMAPKKs were also predicted. ZjMAPKs and ZjMAPKKs were distributed on nine pseudo-chromosomes of Chinese jujube. Subsequently, expression analysis of ZjMAPK and ZjMAPKK genes using reverse transcription PCR and quantitative real-time PCR was carried out. The majority of ZjMAPK and ZjMAPKK genes were expressed in all tested organs/tissues with considerable differences in transcript levels indicating that they might be constitutively expressed. Moreover, ZjMKK5 was specific expressed in early development stage of jujube flower bud, indicating it plays some roles in reproductive organs development. The transcript expression of most ZjMAPK and ZjMAPKK genes was down-regulated in response to plant growth regulators, darkness treatment and phytoplasma infection.ConclusionsWe identified ten ZjMAPK and five ZjMAPKK genes from the genome database of Chinese jujube, the research results shown that ZjMPKs and ZjMKKs have the different expression patterns, indicating that they might play different roles in response to various treatments. The results provide valuable information for the further elucidation of physiological functions and biological roles of jujube MAPKs and MAPKKs.
Highlights
Chinese jujube (Ziziphus jujuba Mill.) is one of the most important members in the Rhamnaceae family
Identification of ZjMAPKs and ZjMAPKKs in Chinese jujube From jujube genome, nine typical Mitogen-activated protein kinases (MAPK) genes and five typical mitogenactivated protein kinases kinases (MAPKK) ones (Table 1) were identified and used for further analysis (All sequences were shown in Additional file 2)
The coding sequence (CDS) length for ZjMAPK genes ranged from 1125 bp (ZjMPK5) to 2166 bp (ZjMPK8), and they encoded proteins ranging from 374 to 721 amino acids in length with an average of 515 aa, with a predicted molecular mass range of 42.63–81.15 KDa, and protein pIs ranging from 5.57 (ZjMPK1) to 9.10 (ZjMPK7) (Table 1)
Summary
Chinese jujube (Ziziphus jujuba Mill.) is one of the most important members in the Rhamnaceae family. There has been no comprehensive analysis of the MAPK and MAPKK gene family in Chinese jujube at the whole genome level. Mitogen-activated protein kinases (MAPK) and mitogenactivated protein kinases kinases (MAPKK) are significant families of serine/threonine kinases, which have been found to involve in wide variety of metabolism pathway include cell division, developmental processes and defense response [1,2,3,4,5]. Plant MAPKs (MPKs) can be divided into four groups (Group A, B, C and D) based on sequence alignment and the phylogenetic analysis, which have two phosphorylation motifs of TEY and TDY. The structure of plant MAPK cascades genes is highly conserved, they have been proved to involve in various biotic and abiotic stresses, hormones, cell division, plant growth and developmental processes. Overexpressing GhMPK16 in Arabidopsis has been indicated that it have significant resistance to bacterial pathogens, fungi, drought and H2O2 [22]
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