bims-polyam 2023-05-14 papers

Issue of 2023–05–14
four papers selected by
Sebastian J. Hofer, University of Graz

Front Plant Sci. 2023 ;14 1076153

Identification of cucumber S-adenosylmethionine decarboxylase genes and functional analysis of CsSAMDC3 in salt tolerance.

Mengliang Zhu, Guangling Chen, Jianqing Wu, Jian Wang, Yu Wang, Shirong Guo, Sheng Shu.

As one of the key enzymes in the biosynthesis of polyamines, S-adenosylmethionine decarboxylase (SAMDC) plays an important role in plant stress resistance. In this study, four SAMDC genes (CsSAMDC1-4) were identified in cucumber (Cucumis sativus L.) and divided into three groups (I, II, and III) by phylogenetic analysis. Motif analysis suggested the existence of many conserved motifs, which is compatible with SAMDC protein classification. Gene structure analysis revealed that CsSAMDC2 and CsSAMDC3 in group I have no intron, which showed a similar response to salt stress by gene expression analysis. CsSAMDC3 responded differently to hormone and stress treatments, and was more susceptible to salt stress. Compared with wild-type (WT) tobacco, the activities of superoxide dismutase, peroxidase, and catalase were increased in CsSAMDC3-overexpressing tobacco under salt stress, but the content of electrolyte leakage, malondialdehyde, and hydrogen peroxide were decreased, which alleviated the inhibition of growth induced by salt stress. Under salt stress, overexpression of CsSAMDC3 in transgenic tobacco plants exhibited salt tolerance, mainly in the form of a significant increase in dry and fresh weight, the maximal quantum yield of PSII photochemistry, the net photosynthetic rate and the content of spermidine and spermine, while the content of putrescine was reduced. In addition, the expression levels of antioxidase-related coding genes (NtSOD, NtPOD, NtCAT) and PAs metabolism-related coding genes (NtSAMS, NtSPDS, NtSPMS, NtPAO) in transgentic plants was lower than WT under salt stress, which suggested that overexpression of CsSAMDC3 affected the expression of these genes. In summary, our results showed that CsSAMDC3 could be used as a potential candidate gene to improve salt tolerance of cucumber by regulating polyamine and antioxidant metabolism.

Keywords: CsSAMDC3; antioxidant metabolism; cucumber; polyamines; salt stress

DOI: https://doi.org/10.3389/fpls.2023.1076153

J Agric Food Chem. 2023 May 09.

Identification and Biosynthetic Study of the Siderophore Lysochelin in the Biocontrol Agent Lysobacter enzymogenes.

Amanda Lynn Miller, Shanren Li, Catherine D Eichhorn, Yongbiao Zheng, Liangcheng Du.

Lysobacter is a genus of bacteria emerging as new biocontrol agents in agriculture. Although iron acquisition is essential for the bacteria, no siderophore has been identified from any Lysobacter. Here, we report the identification of the first siderophore, N1,N8-bis(2,3-dihydroxybenzoyl)spermidine (lysochelin), and its biosynthetic gene cluster from Lysobacter enzymogenes. Intriguingly, the deletion of the spermidine biosynthetic gene encoding arginine decarboxylase or SAM decarboxylase eliminated lysochelin and the antifungals, HSAF and its analogues, which are key to the disease control activity and to the survival of Lysobacter under oxidative stresses caused by excess iron. The production of lysochelin and the antifungals is greatly affected by iron concentration. Together, the results revealed a previously unrecognized system, in which L. enzymogenes produces a group of small molecules, lysochelin, spermidine, and HSAF and its analogues, that are affected by iron concentration and critical to the growth and survival of the biocontrol agent.

Keywords: Lysobacter enzymogenes; antifungal HSAF; biocontrol; siderophore; spermidine

DOI: https://doi.org/10.1021/acs.jafc.3c01250

bioRxiv. 2023 Apr 24. pii: 2023.04.24.537996. [Epub ahead of print]

Deoxyhypusine synthase is required for the translational regulation of pancreatic beta cell maturation.

Craig T Connors, Emily K Anderson-Baucum, Spencer Rosario, Catharina B P Villaca, Caleb D Rutan, Paul J Childress, Leah R Padgett, Morgan A Robertson, Teresa L Mastracci.

As professional secretory cells, beta cells require adaptable mRNA translation to facilitate a rapid synthesis of proteins, including insulin, in response to changing metabolic cues. Specialized mRNA translation programs are essential drivers of cellular development and differentiation. However, in the pancreatic beta cell, the majority of factors identified to promote growth and development function primarily at the level of transcription. Therefore, despite its importance, the regulatory role of mRNA translation in the formation and maintenance of functional beta cells is not well defined. In this study, we have identified a translational regulatory mechanism in the beta cell driven by the specialized mRNA translation factor, eukaryotic initiation factor 5A (eIF5A), which facilitates beta cell maturation. The mRNA translation function of eIF5A is only active when it is post-translationally modified ("hypusinated") by the enzyme deoxyhypusine synthase (DHPS). We have discovered that the absence of beta cell DHPS in mice reduces the synthesis of proteins critical to beta cell identity and function at the stage of beta cell maturation, leading to a rapid and reproducible onset of diabetes. Therefore, our work has revealed a gatekeeper of specialized mRNA translation that permits the beta cell, a metabolically responsive secretory cell, to maintain the integrity of protein synthesis necessary during times of induced or increased demand.
ARTICLE HIGHLIGHTS: Pancreatic beta cells are professional secretory cells that require adaptable mRNA translation for the rapid, inducible synthesis of proteins, including insulin, in response to changing metabolic cues. Our previous work in the exocrine pancreas showed that development and function of the acinar cells, which are also professional secretory cells, is regulated at the level of mRNA translation by a specialized mRNA translation factor, eIF5A HYP . We hypothesized that this translational regulation, which can be a response to stress such as changes in growth or metabolism, may also occur in beta cells. Given that the mRNA translation function of eIF5A is only active when the factor is post-translationally modified ("hypusinated") by the enzyme deoxyhypusine synthase (DHPS), we asked the question: does DHPS/eIF5A HYP regulate the formation and maintenance of functional beta cells? We discovered that in the absence of beta cell DHPS in mice, eIF5A is not hypusinated (activated), which leads to a reduction in the synthesis of critical beta cell proteins that interrupts pathways critical for identity and function. This translational regulation occurs at weaning age, which is a stage of cellular stress and maturation for the beta cell. Therefore without DHPS/eIF5A HYP , beta cells do not mature and mice progress to hyperglycemia and diabetes. Our findings suggest that secretory cells have a mechanism to regulate mRNA translation during times of cellular stress. Our work also implies that driving an increase in mRNA translation in the beta cell might overcome or possibly reverse the beta cell defects that contribute to early dysfunction and the progression to diabetes.

DOI: https://doi.org/10.1101/2023.04.24.537996

Oncol Lett. 2023 Jun;25(6): 246

SHCBP1 contributes to the proliferation and self‑renewal of cervical cancer cells and activation of the NF‑κB signaling pathway through EIF5A.

Boya Deng, Ailin Li, Ying Zhu, Yingying Zhou, Jing Fei, Yuan Miao.

Cervical cancer (CC) is the most common human papillomavirus-related disease. Continuous activation of the NF-κB signaling pathway has been observed in CC. SHC binding and spindle associated 1 (SHCBP1) contributes to tumorigenesis and activation of the NF-κB pathway in multiple cancer types, while its function in CC remains unclear. In the present study, three Gene Expression Omnibus datasets were used to identify differentially expressed genes (DEGs) in CC. Loss- and gain-of-function experiments were performed using stable SHCBP1-silenced and SHCBP1-overexpressing CC cells. To further explore the molecular mechanism of SHCBP1 in CC, small interfering RNA targeting eukaryotic translation initiation factor 5A (EIF5A) was transfected into stable SHCBP1-overexpressing CC cells. The results demonstrated that SHCBP1 was an upregulated DEG in CC tissues compared with healthy control cervical tissues. Functional experiments revealed the pro-proliferative and pro-stemness role of SHCBP1 in CC cells (CaSki and SiHa cells), in vitro. Furthermore, the NF-κB signaling pathway in CC cells was activated by SHCBP1. Increases in cell proliferation, stemness and activation of NF-κB, induced by SHCBP1 overexpression in CC cells, were reversed by EIF5A knockdown. Taken together, the results indicated that SHCBP1 serves an important role in regulation of CC cell proliferation, self-renewal and activation of NF-κB via EIF5A. The present study demonstrated a potential molecular mechanism underlying the progression of CC.

Keywords: SH2 domain-binding protein; cervical cancer; eukaryotic translation initiation factor 5A; nuclear factor-κB

DOI: https://doi.org/10.3892/ol.2023.13832