Molecular characterization, expression analysis and heterologous expression of two translationally controlled tumor protein genes from Cucumis sativus

Abstract

The translationally controlled tumor protein (TCTP) is a family of abundant and ubiquitous proteins involved in several important primary functions. Cucumbers harbor two TCTP genes, CsTCTP1 and CsTCTP2; however, their functional roles remain unclear. In this study, we isolated CsTCTP1 and CsTCTP2 (XP-004134215 and XP-004135602, respectively) promoters, full-length cDNA and genomic sequences from Cucumis sativus. Bioinformatics analysis, containing cis-acting elements, structural domains, phylogenetic tree and conserved motifs, suggested the conservation and divergence of CsTCTP1 and CsTCTP2, thus providing knowledge regarding their functions. Expression analysis indicated that CsTCTP1 and CsTCTP2 exhibited tissue-specific expression and were regulated by biotic or abiotic stresses in C. sativus. Furthermore, CsTCTP1 and CsTCTP2 were regulated by ABA and may be associated with the TOR (target of rapamycin) signaling pathway. In a prokaryotic expression analysis, CsTCTP1 and CsTCTP2 showed positive responses to salt and heat stresses and a negative response to drought and HgCl2 stresses. TCTP may exert multiple functions in various cellular processes.

The Two Translationally Controlled Tumor Protein Genes, CsTCTP1 and CsTCTP2, Are Negative Modulators in the Cucumis sativus Defense Response to Sphaerotheca fuliginea

“…To elucidate whether CsTCTP1 / CsTCTP2 -mediated resistance against S. fuliginea is related to pathogen-associated genes, we examined the transcriptional responses of four known S. fuliginea -related defense genes, including 14-3-3 (XM-004136782.2), chitinase (HM015248), PR-1a (AF475286), and CuPi1 (U93586.1), to silencing and overexpression of CsTCTP1 / CsTCTP2 in non-infested cucumber plants by qRT-PCR ( Figure 5 ). CuPi1 , a phloem lectin protein, was more abundant in B21-a-2-2-2 (an S. fuliginea -susceptible genotype) than in B21-a-2-1-2 ( Meng et al, 2017 ). The level of chitinase transcripts was significantly higher in CsTCTP1 -silenced plants than in TRV:00-injected plants, whereas it was significantly lower in CsTCTP1 -overexpressing cucumbers than in LUC:00-injected cucumbers.…”

“…These data indicated that both CsTCTP1 and CsTCTP2 act as negative modulators in the cucumber defense response to S. fuliginea . Notably, overexpression of CsTCTP1 reduced the tolerance to high temperature stress, while overproduction of CsTCTP2 enhanced the resistance to high temperature stress ( Meng et al, 2017 ). Since the function of CsTCTP1 and CsTCTP2 genes may be similar but do not overlap completely, further study of CsTCTP1 and CsTCTP2 regulatory mechanisms is necessary.…”

“…The exogenous application of ABA suppresses the resistance of plants to pathogens ( Cao et al, 2011 ). The transcription level of CsTCTP1 significantly upregulated after treatment with ABA ( Meng et al, 2017 ). Furthermore, augmented expression of the CsTCTP1 gene in cucumber cotyledons results in decreased resistance to S. fuliginea.…”

“…Cucumber has 2 TCTP genes, CsTCTP1 (XP-004134215) and CsTCTP2 (XP-004135602). Though CsTCTP1 and CsTCTP2 share a high degree of homology, the functions of CsTCTPs to different abiotic stresses may differ ( Meng et al, 2017 ). The molecular and biochemical mechanisms by which TCTP functions in response to S. fuliginea have not been completely established.…”

“…CsTCTP1 and CsTCTP2 are both regulated by exogenous abscisic acid (ABA) treatment ( Meng et al, 2017 ). Moreover, AtTCTP overexpression enhanced drought tolerance in Arabidopsis and played a role in ABA-mediated stomatal movement ( Kim et al, 2012 ).…”