Backgrounds: C2H2-type zinc finger protein (ZFPs) form a relatively large family of transcriptional regulators in plants, and play many roles in plant growth, development, and stress response. However, the comprehensive analysis of C2H2 ZFPs in cucumber (CsZFPs) and their regulation function in cucumber are still lacking. Results: In the current study, the whole genome identification and characterization of CsZFPs, including the gene structure, genome localization, phylogenetic relationship, and gene expression were performed. Functional analysis of 4 selected genes by transient transformation were also conducted. A total of 129 full-length CsZFPs were identified, which could be classified into four groups according to the phylogenetic analysis. The 129 CsZFPs unequally distributed on 7 chromosomes. Promoter cis-element analysis showed that the CsZFPs might involve in the regulation of phytohormone and/or abiotic stress response, and 93 CsZFPs were predicted to be targeted by one to 20 miRNAs. Moreover, the subcellular localization analysis indicated that 10 tested CsZFPs located in the nucleus and the transcriptome profiling analysis of CsZFPs demonstrated that these genes are involved in root and floral development, pollination and fruit spine. Furthermore, the transient overexpression of Csa1G085390 and Csa7G071440 into Nicotiana benthamiana plants revealed that they could decrease and induce leave necrosis in response to pathogen attack, respectively, and they could enhance salt and drought stresses through the initial induction of H₂O₂. In addition, Csa4G642460 and Csa6G303740 could induce cell death after 5 days transformation. Conclusions: The identification and function analysis of CsZFPs demonstrated that some key individual CsZFPs might play essential roles in response to biotic and abiotic stresses. These results could lay the foundation for understanding the role of CsZFPs in cucumber development for future genetic engineering studies.

Backgrounds: Cyclic nucleotide gated channels (CNGCs) play multifaceted roles in plant physiological processes, especially with respect to signalling processes, plant development, and responses to environmental stresses. However, little information is known about the CNGC family in the large cosmopolitan familyRhamnaceae, which has strong tolerance to biotic and abiotic stresses.Results: In the current study, a total of 15ZjCNGCswhich located on 7 chromosomes were firstly identified in Chinese jujube (Ziziphus jujubaMill.), the most important species ofRhamnaceaein terms of economic and ecological values. Phylogenetic analysis showed that theseZjCNGCscould be classified into four groups,ZjCNGC12belonged to group IVA, andZjCNGC13,14,15belonged to group IVB. In addition, the paralogous and orthologous homology duplication ofZjCNGC15occurred during the evolutionary process. The characteristics ofZjCNGCsregarding to exon-intron numbers and post-translational modifications showed diversified structures and functions. Motif composition and protein sequence analysis revealed that the phosphate-binding cassette and hinge regions were conserved among ZjCNGCs. Prediction of thecis-acting regulatory elements and expression profiles by real-time quantitative PCR analysis showed that some of theZjCNGCsresponded to environmental changes, especiallyZjCNGC2, which was significantly downregulated in response to cold stress, andZjCNGC4was highly induced in response to cold, salt and alkaline stresses.ZjCNGC13and14were highly induced in the phytoplasma-resistant cultivar and downregulated in the susceptible cultivar. Furthermore,ZjCNGC2could be regulated by cAMP treatment, microtubule changes and interact with ZjMAPKK4, which suggested that cAMP and microtubule might play important roles inZjCNGC2mediatedZjMAPKK4signalling transduction involved in cold stress.Conclusions: The identification and classification analysis ofZjCNGCswere firstly reported, and some key individualZjCNGCsmight play essential roles in the response to biotic and abiotic stresses, especiallyZjCNGC2mediatedZjMAPKK4signalling transduction involved in cold stress. This systematic analysis could provide important information for further functional characterization ofZjCNGCswith the aim of breeding stress-resistant cultivars.

Melatonin (MT) plays an important role in plant growth and development, and response to biotic and abiotic stresses. Salt stress is one of the major abiotic stresses affecting plant growth and distribution. Sour jujube mainly grows in mountainous sandy land and faces the threat of salt stress. Thus, to explore whether exogenous MT application could improve the salt stress tolerance of sour jujube and reveal the molecular mechanism behind it, the phenotypic and transcriptomic analyses of different concentrations of MT treatments prior to sodium chloride (NaCl) treatment to sour jujube was investigated. Firstly, exogenous MT treatment has a certain alleviating effect on salt stress induced damage of sour jujube. Transcriptome analysis showed that 6,292, 2,795, and 4,198 differentially expressed genes (DEGs) were identified in water treatment (W) vs 400 mmol/L NaCl treatment (Na), W vs 10 µmol/L MT plus 400 mmol/L NaCl treatment (MNa), and Na vs MNa comparative groups, respectively. KEGG enrichment analysis of DEGs showed that multiple metabolic pathways were involved in MT regulated effect on salt stress, including mitogen-activated protein kinase (MAPK) signaling pathway, phosphatidylinositol signaling system, and plant hormone signal transduction pathways etc. In addition, some transcription factor families, such as MYB, WRKY, and NAC, were also activated by exogenous MT treatment under salt stress. The results suggest that MT can improve the tolerance of sour jujube to salt stress mainly through the regulation of MAPK, hormone signaling pathways, and related transcription factors, which could lay the foundation for further study on the molecular mechanisms of how exogenous MT regulates salt stress tolerance in sour jujube.

Background: Mitogen-activated protein kinase (MAPK) cascades play vital roles in signal transduction in response to a wide range of biotic and abiotic stresses. In a previous study, we identified ten ZjMAPKs and five ZjMAPKKs in the Chinese jujube genome. We found that some members of ZjMAPKs and ZjMAPKKs may play key roles in the plant’s response to phytoplasma infection. However, how these ZjMAPKKs are modulated by ZjMAPKKKs during the response process has not been elucidated. Little information is available regarding MAPKKKs in Chinese jujube. Results: A total of 56 ZjMAPKKKs were identified in the jujube genome. All of these kinases contain the key S-TKc (serine/threonine protein kinase) domain, which is distributed among all 12 chromosomes. Phylogenetic analyses show that these ZjMAPKKKs can be classified into two subfamilies. Specifically, 41 ZjMAPKKKs belong to the Raf subfamily, and 15 belong to the MEKK subfamily. In addition, the ZjMAPKKKs in each subfamily share the same conserved motifs and gene structures. Only one pair of ZjMAPKKKs (15/16, on chromosome 5) was found to be tandemly duplicated. Using qPCR, the expression profiles of these MAPKKKs were investigated in response to infection with phytoplasma. In the three main infected tissues (witches’ broom leaves, phyllody leaves, and apparently normal leaves), ZjMAPKKK26 and − 45 were significantly upregulated, and ZjMAPKKK3, − 43 and − 50 were significantly downregulated. ZjMAPKKK4, − 10, − 25 and − 44 were significantly and highly induced in sterile cultivated tissues infected by phytoplasma, while ZjMAPKKK6, − 7, − 17, − 18, − 30, − 34, − 35, − 37, − 40, − 41, − 43, − 46, − 52 and − 53 were significantly downregulated. Conclusions: For the first time, we present an identification and classification analysis of ZjMAPKKKs. Some ZjMAPKKK genes may play key roles in the response to phytoplasma infection. This study provides an initial understanding of the mechanisms through which ZjMAPKKKs are involved in the response of Chinese jujube to phytoplasma infection.