bims-polyam 2023-10-08 papers

Issue of 2023–10–08
four papers selected by
Sebastian J. Hofer, University of Graz

Funct Plant Biol. 2023 Oct 04.

Effects of water stress on endogenous hormones and free polyamines in different tissues of grapevines (Vitis vinifera L. cv. 'Merlot').

Zhennan Zhan, Ning Wang, Zumin Chen, Yanxia Zhang, Kangqi Geng, Dongmei Li, Zhenping Wang.

Water stress can affect plant ecological distribution, crop growth and carbohydrate distribution, impacting berry quality. However, previous studies mainly focused on short-term water stress or osmotic stress and few studies paid attention to the responses of grape to long-term water stresses. Grapevines were subjected to no water stress (CK), mild water stress (T1) and moderate water stress (T2). Hundred-berry weight and malic acid content were reduced under T1 and T2; however, glucose and fructose content showed the opposite trend. Endogenous hormones and polyamines (PAs) can regulate plant growth and development as well as physiological metabolic processes. T1 and T2 could increase abscisic acid content, however, indole-3-acetic acid, jasmonate, gibberellins 3 and 4, cytokinin and trans-zeatin contents were slightly decreased. Three species of PAs (putrescine, spermidine and spermine) were detected, presenting obvious tissue specificity. Furthermore, there was a statistically positive correlation relating spermidine content in the pulp with glucose and fructose contents of grape berries; and a negative correlation with organic acid. In summary, water stress had a profound influence on hormonally-driven changes in physiology and berry quality, indicating that endogenous hormones and the PAs play a critical role in the development and ripening of grape berries under water stress.

DOI: https://doi.org/10.1071/FP22225

Front Plant Sci. 2023 ;14 1230331

Spermidine enhances heat tolerance of rice seeds during mid-filling stage and promote subsequent seed germination.

Yutao Huang, Gaofu Mei, Dongdong Cao, Yebo Qin, Liu Yang, Xiaoli Ruan.

Introduction: Heat stress is a vital factor which restricts rice seed quality and yield. However, the response mechanism to heat stress in the mid filling stage of rice seed is unclear.
Methods: In the present study we integrated phenotypic analysis with biochemical, hormone, and gene expression analysis in order to explore technologies for improving rice seeds heat tolerance and subsequent seed germination.
Results: Spermidine (Spd) application effectively alleviated the damage of heat stress treatment during mid-filling stage (HTM, 12-20 days after pollination) on seed development, promoted subsequent seed germination and seedlings establishment. Spd significantly increased seed dry weight, starch and amylose contents during seed development under heat stress, and improved seed germinate, seedlings establishment and seedling characteristics during germination time. Biochemical analysis indicated that, HTM significantly decreased the activities of several starch synthase enzymes and led to a decrease in starch content. While Spd treatment significantly enhanced the activities of ADP-glucose pyrophosphorylas and granule-bound starch synthase, as well as the corresponding-genes expressions in HTM rice seeds, resulting in the increases of amylose and total starch contents. In addition, Spd significantly increased the catalase and glutathione reductase activities together with corresponding-genes expressions, and lowered the overaccumulation of H2O2 and malondialdehyde in HTM seeds. In the subsequent seed germination process, HTM+Spd seeds exhibited dramatically up-regulated levels of soluble sugars, glucose, ATP and energy charges. Consistently, HTM+Spd seeds showed significantly increased of α-amylose and α-glucosidase activities as well as corresponding-genes expressions during early germination. Moreover, HTM evidently increased the abscisic acid (ABA) content, decreased the gibberellin (GA) content, and accordingly significantly declined the GA/ABA ratio during early rice seeds germination. However, Spd treatment did not significantly affect the metabolism of GA and ABA in seed germination stage.
Discussion: The present study suggested that Spd treatment could effectively alleviate the negative impact of HTM on seed development and the subsequent seed germination, which might be closely correlated with starch synthesis and antioxidant defense during seed filling period, starch decomposition and energy supply in seed germination period.

Keywords: antioxidant defense; heat stress; rice; seed development; seed germination; spermidine; starch

DOI: https://doi.org/10.3389/fpls.2023.1230331

Am J Physiol Gastrointest Liver Physiol. 2023 Oct 03.

Stabilization of Cx43 mRNA via RNA-binding protein HuR regulated by polyamines enhances intestinal epithelial barrier function.

Shelley R Wang, Caroline G Mallard, Cassandra A Cairns, Hee Kyoung Chung, Dongyoon Yoo, Suraj K Jaladanki, Lan Xiao, Jian-Ying Wang.

Gut barrier dysfunction occurs commonly in patients with critical disorders, leading to the translocation of luminal toxic substances and bacteria to the bloodstream. Connexin 43 (Cx43) acts as a gap junction protein and is crucial for intercellular communication and the diffusion of nutrients. The levels of cellular Cx43 are tightly regulated by multiple factors, including polyamines, but the exact mechanism underlying the control of Cx43 expression remains largely unknown. The RNA-binding protein HuR regulates the stability and translation of target mRNAs and is involved in many aspects of intestinal epithelial pathobiology. Here we show that HuR directly bound to Cx43 mRNA via its 3'-untranslated region in intestinal epithelial cells (IECs) and this interaction enhanced Cx43 expression by stabilizing Cx43 mRNA. Depletion of cellular polyamines inhibited the [HuR/Cx43 mRNA] complex and decreased the level of Cx43 protein by destabilizing its mRNA, but these changes were prevented by ectopic overexpression of HuR. Polyamine depletion caused intestinal epithelial barrier dysfunction, which was reversed by ectopic Cx43 overexpression. Moreover, overexpression of Chk2 in polyamine-deficient cells increased the [HuR/Cx43 mRNA] complex, elevated Cx43 levels, and promoted barrier function. These findings indicate that Cx43 mRNA is a novel target of HuR in IECs and that polyamines regulate Cx43 mRNA stability via HuR, thus playing a critical role in the maintenance of intestinal epithelial barrier function.

Keywords: Chk2 phosphorylation; Polyamines; RNA-binding proteins; gut barrier function; mRNA stability

DOI: https://doi.org/10.1152/ajpgi.00143.2023

FEMS Microbiol Lett. 2023 Oct 05. pii: fnad096. [Epub ahead of print]

A novel synthetic inhibitor of polyamine utilization in S. coelicolor.

Sergii Krysenko, Maria Lopez, Christian Meyners, Patrick L Purder, Alina Zinser, Felix Hausch, Wolfgang Wohlleben.

In this work, we present the first inhibitor of GlnA2Sc, a gamma-glutamylpolyamine synthetase, which allows S. coelicolor to detoxify high concentrations of polyamines and to utilize them as a carbon or nitrogen source. GlnA2 belongs to the class of glutamine-synthetase-like (GS-like) enzymes that catalyze the glutamylation of different nitrogen-containing compounds. Whereas a number of inhibitors for glutamine synthetases are known, none of them are known to inhibit GlnA2. In this work, PPU 268 an inhibitor for GlnA2 is presented that is structurally derived from the prototypic GS inhibitor-methionine sulfoximine (MSO). It combines two features: the binding mechanism of MSO and the amine substrate specificity of GlnA2Sc. This inhibitor is a novel compound to block the polyamine utilization in bacteria resulting in the inability to detoxify polyamines. This may offer a possibility to develop novel therapeutic strategies to combat actinobacterial human pathogens that encounter polyamines in the course of the infection processes.

Keywords: S. coelicolor ; GlnA2; bacterial enzyme inhibitors; bacterial physiology; gamma-glutamylpolyamine synthetase; polyamine metabolism

DOI: https://doi.org/10.1093/femsle/fnad096