Arabidopsis CPR5 Plays a Role in Regulating Nucleocytoplasmic Transport of mRNAs in Ethylene Signaling Pathway

The ETR1 receptor plays a predominant role in ethylene signaling in Arabidopsis thaliana. Previous studies showed that both RTE1 and CPR5 can directly bind to the ETR1 receptor and regulate ethylene signaling. RTE1 was suggested to promote the ETR1 receptor signaling by influencing its conformation, but little is known about the regulatory mechanism of CPR5 in ethylene signaling. In this study, we presented data showing that both RTE1 and CPR5 bound to the N-terminal domains of ETR1, and regulated ethylene signaling via the ethylene receptor. On the other hand, the research provided evidence indicating that CPR5 could act as a nucleoporin to regulate the ethylene-related mRNAs export out of the nucleus, while RTE1 or its homolog (RTH) had no effect on the nucleocytoplasmic transport of mRNAs. Nuclear qRT-PCR analysis and poly(A)-mRNA in situ hybridization showed that defect of CPR5 restricted nucleocytoplasmic transport of mRNAs. These results advance our understanding of the regulatory mechanism of CPR5 in ethylene signaling.

Isolation of the ZmERS4 Gene From Maize and Its Functional Analysis in Transgenic Plants

A gene encoding a protein similar to ethylene receptor was isolated from maize (Zea mays L.), which was named as ZmERS4.The gene was 1,905 bp in length with an open reading frame that encoded a protein consisting of 634 amino acids. The homologous analysis showed that ZmERS4 shared high similarity with the ethylene receptor protein, OsERS1, from rice (Oryza sativa L.). ZmERS4 grouped into the ETR1 subfamily of ethylene receptors based on its conserved domain and phylogenetic status. Tissue-specific and induced expression analyses indicated that ZmERS4 was differentially expressed in maize tissues, predominantly in the stems and leaves, and was induced by salicylic acid (SA). Overexpression of ZmERS4 in Arabidopsis improved resistance against the bacterial pathogen, PstDC3000, by inducing the expression of SA signaling-related genes. Moreover, treatment with flg22 induced the expression of the defense-related gene, PR1, in maize protoplasts that transiently expressed ZmERS4. Furthermore, the ultra-high-performance liquid chromatography (UPLC) analysis showed that the SA contents in ZmERS4-overexpressing Arabidopsis lines were significantly higher than the control lines. Additionally, the improved resistance of ZmERS4-overexpressing Arabidopsis against PstDC3000 was blocked after pretreatment with the SA biosynthetic inhibitor, ABT. Based on the collective findings, we hypothesize that ZmERS4 plays an important role in disease resistance through SA-mediated signaling pathways.

Arabidopsis CPR5 regulates ethylene signaling via interacting with ETR1 N-terminus and controlling mRNAs nucleocytoplasmic transport

ETR1 is the major ethylene receptor in Arabidopsis thaliana. Previous studies showed that RTE1 and CPR5 can bind to ETR1 and play regulatory roles in ethylene signaling. RTE1 has been suggested to promote ETR1 signal transduction by influencing the conformation of ETR1, but little is known about the mechanism of CPR5 on the regulation of ETR1 signaling. In this study, we showed that both CPR5 and RTE1 could interact with the N-terminal transmembrane domains of ETR1, and CPR5 needs at least three transmembrane domains of ETR1 while RTE1 needs only two for the binding. As CPR5 has also been shown to be localized in the nuclear membrane and might act as a nucleoporin, we analyzed the effects of CPR5 on the nucleocytoplasmic transport of ethylene-related mRNAs using poly(A)-mRNA in situ hybridization and real-time quantitative PCR (qPCR), and the results indicated that CPR5 could selectively regulate the nucleocytoplasmic transport of mRNAs in ethylene signaling pathway. In contrast, the nucleoporin mutants (nup160, nup96-1 and nup96-2) dramatically accumulated all the examined mRNAs in the nucleus. In conclusion, the present study provides evidence demonstrating that CPR5 regulates ethylene signaling through interacting with the ETR1 receptor and controlling the mRNAs nucleocytoplasmic transport in ethylene signaling pathway.Key messageThis study reveals that CPR5 is involved in the regulation of ethylene signaling via two different ways: interacting with the N-terminal domains of ERT1 and controlling the nucleocytoplasmic transport of mRNAs in ethylene signaling pathway.

Identification and Expression Analysis of Gretchen Hagen 3 (GH3) in Kiwifruit (Actinidia chinensis) During Postharvest Process

In plants, the Gretchen GH3 (GH3) protein is involved in free auxin (IAA) and amino acid conjugation, thus controlling auxin homeostasis. To date, many GH3 gene families have been identified from different plant species. However, the GH3 gene family in kiwifruit (Actinidia chinensis) has not been reported. In this study, 12 AcGH3 genes were identified, phylogenetic analysis of AtGH3 (Arabidopsis), SlGH3 (Solanum lycopersicum), and AcGH3 provided insights into various orthologous relationships among these proteins, which were categorized into three groups. Expression analysis of AcGH3 genes at different postharvest stages suggested limited or no role for most of the AcGH3 genes at the initiation of fruit ripening. AcGH3.1 was the only gene exhibiting ripening-associated expression. Further study showed that the expression of AcGH3.1 gene was induced by NAA (1-naphthylacetic acid, auxin analogue) and inhibited by 1-MCP (1-methylcyclopropene, ethylene receptor inhibitor), respectively. AcGH3.1 gene silencing inhibited gene expression and delayed fruit softening in kiwifruit. The results indicate that AcGH3.1 may play an important role in the softening process of fruits. Analysis of the AcGH3.1 promoter revealed the presence of many cis-elements related to hormones, light, and drought. The determination of GUS (β-Galactosidase) enzyme activity revealed that promoter activity increased strikingly upon abscisic acid (ABA), ethylene, or NAA treatment, and significantly decreased with salicylic acid (SA) treatment. The present study could help in the identification of GH3 genes and revelation of AcGH3.1 gene function during postharvest stages, which pave the way for further functional verification of the AcGH3.1 gene.