bims-polyam Biomed News
on Polyamines
Issue of 2020‒03‒22
three papers selected by
Alexander Ivanov
Engelhardt Institute of Molecular Biology

  1. J Biochem. 2020 Mar 17. pii: mvaa032. [Epub ahead of print]
    Oguro A, Shigeta T, Machida K, Suzuki T, Iwamoto T, Matsufuji S, Imataka H.
      Antizyme interacts with ornithine decarboxylase, which catalyzes the first step of polyamine biosynthesis and recruits it to the proteasome for degradation. Synthesizing the functional antizyme protein requires transition of the reading frame at the termination codon. This programmed +1 ribosomal frameshifting is induced by polyamines, but the molecular mechanism is still unknown. In this study, we explored the mechanism of polyamine-dependent +1 frameshifting using a human cell-free translation system. Unexpectedly, spermidine induced +1 frameshifting in the mutants replacing the termination codon at the shift site with a sense codon. Truncation experiments showed that +1 frameshifting occurred promiscuously in various positions of the antizyme sequence. The probability of this sequence-independent +1 frameshifting increased in proportion to the length of the open reading frame. Furthermore, the +1 frameshifting was induced in some sequences other than the antizyme gene in a polyamine-dependent manner. These findings suggest that polyamines have the potential to shift the reading frame in the +1 direction in any sequence. Finally, we showed that the probability of the sequence-independent +1 frameshifting by polyamines is likely inversely correlated with translation efficiency. Based on these results, we propose a model of the molecular mechanism for antizyme +1 frameshifting.
    Keywords:  human cell-free translation system; polyamine; ribosomal frameshifting; spermidine; translation control
  2. Plant Cell Environ. 2020 Mar 16.
    Liu J, Yang R, Jian N, Wei L, Ye L, Wang R, Gao H, Zheng Q.
      Brassinosteroids (BRs) are known to improve salt tolerance of plants, but not in all situations. Here, we show that a certain concentration of 24-epibrassinolide (EBL), an active BR, can promote the tolerance of canola under high salt stress, but the same concentration is disadvantageous under low salt stress. We define this phenomenon as hormonal stress-level-dependent biphasic (SLDB) effects. The SLDB effects of EBL on salt tolerance in canola are closely related to H2 O2 accumulation, which is regulated by polyamine metabolism, especially putrescine (Put) oxidation. The inhibition of EBL on canola under low salt stress can be ameliorated by repressing Put biosynthesis or diamine oxidase activity to reduce H2 O2 production. Genetic and phenotypic results of bri1-9, bak1, bes1-D, and bzr1-1D mutants and over-expression lines of BRI1 and BAK1 in Arabidopsis indicate that a proper enhancement of BR signaling benefits plants in countering salt stress, whereas excessive enhancement is just as harmful as a deficiency. These results highlight the involvement of crosstalk between BR signaling and Put metabolism in H2 O2 accumulation, which underlies the dual role of BR in plant salt tolerance. This article is protected by copyright. All rights reserved.
    Keywords:  biphasic effect; brassinosteroids; hydrogen peroxide; polyamines; salt stress
  3. Int J Mol Sci. 2020 Mar 09. pii: E1857. [Epub ahead of print]21(5):
    Zhu MD, Zhang M, Gao DJ, Zhou K, Tang SJ, Zhou B, Lv YM.
      Drought is a serious problem, which causes heavy yield losses for rice. Heat-shock factors (HSFs) had been implicated in tolerance to drought and high temperature. However, there has not been much functional characterization and mechanism clarification in rice. Previously, we found an HSF gene, OsHSFA3, was highly related with drought tolerance after screening from 10,000 different samples. Herein, we cloned the OsHSFA3 from rice and overexpressed it in Arabidopsis thaliana to study its regulatory mechanism of drought tolerance. Phenotypic and physiological assays of the transgenic Arabidopsis lines showed that overexpression of OsHSFA3 confers drought tolerance by reducing water loss and reactive oxygen species (ROS) levels, whereas it increases abscisic acid (ABA) levels. However, enzymatic antioxidants such as activity levels of superoxide dismutase, peroxidase and catalase were not significantly different between wild type and transgenic lines. Instead, we observed a significant increase in polyamine content, which was correlated with increased AtADC1, AtADC2, SPDS1 and SPMS expression levels. In silico and in vivo analyses confirmed that OsHSFA3 is a nuclear-localized gene. In addition, OsHSFA3 can bind to the promoter of AtADC1 and OsADC via a yeast one-hybrid assay. Overall, this study reveals that OsHSFA3 improves drought tolerance in Arabidopsis not only by increasing ABA levels, but also by modulating polyamine levels to maintain ROS homeostasis, therefore it could be a strong candidate to develop drought-tolerant rice cultivars.
    Keywords:  abscisic acid; drought; gene expression; polyamines; reactive oxygen species