Aldehyde oxidase (AO; EC 1.2.3.1) activity was measured in seedlings of wild type or an auxin-overproducing mutant, superroot1 (sur1), of Arabidopsis thaliana. Activity staining for AO after native polyacrylamide gel electrophoresis separation of seedling extracts revealed that there were three major bands with AO activity (AO1-3) in wild-type and mutant seedlings. One of them (AO1) had a higher substrate preference for indole-3-aldehyde. This AO activity was significantly higher in sur1 mutant seedlings than in the wild type. The difference in activity was most apparent 7 d after germination, the same time required for the appearance of the remarkable sur1 phenotype, which includes epinastic cotyledons, elongated hypocotyls, and enhanced root development. Higher activity was observed in the root and hypocotyl region of the mutant seedlings. We also assayed the indole-3-acetaldehyde oxidase activity in extracts by high-performance liquid chromatography detection of indole-3-acetic acid (IAA). The activity was about 5 times higher in the extract of the sur1 seedlings, indicating that AO1 also has a substrate preference for abscisic aldehyde. Treatment of the wild-type seedlings with picloram or IAA caused no significant increase in AO1 activity. This result suggested that the higher activity of AO1 in sur1 mutant seedlings was not induced by IAA accumulation and, thus, strongly supports the possible role of AO1 in IAA biosynthesis in Arabidopsis seedlings.

Higher activity of an aldehyde oxidase in the auxin-overproducing superroot1 mutant of Arabidopsis thaliana. [Erratum: Apr 1998, v. 116 (4), p. 1607.]

This review highlights the most recent updated information available about Zn phytotoxicity at physiological, biochemical and molecular levels, uptake mechanisms as well as excess Zn homeostasis in plants. Zinc (Zn) is a natural component of soil in terrestrial environments and is a vital element for plant growth, as it performs imperative functions in numerous metabolic pathways. However, potentially noxious levels of Zn in soils can result in various alterations in plants like reduced growth, photosynthetic and respiratory rate, imbalanced mineral nutrition and enhanced generation of reactive oxygen species. Zn enters into soils through various sources, such as weathering of rocks, forest fires, volcanoes, mining and smelting activities, manure, sewage sludge and phosphatic fertilizers. The rising alarm in environmental facet, as well as, the narrow gap between Zn essentiality and toxicity in plants has drawn the attention of the scientific community to its effects on plants and crucial role in agricultural sustainability. Hence, this review focuses on the most recent updates about various physiological and biochemical functions perturbed by high levels of Zn, its mechanisms of uptake and transport as well as molecular aspects of surplus Zn homeostasis in plants. Moreover, this review attempts to understand the mechanisms of Zn toxicity in plants and to present novel perspectives intended to drive future investigations on the topic. The findings will further throw light on various mechanisms adopted by plants to cope with Zn stress which will be of great significance to breeders for enhancing tolerance to Zn contamination.

Zinc toxicity in plants: a review.

Zinc oxide (ZnO) nanoparticles (nZnO) are among the most commonly used nanoparticles (NPs), and they have been shown to have harmful effects on plants. However, the molecular mechanisms underlying ...

Comparative Physiological and Transcriptomic Analyses Reveal the Toxic Effects of ZnO Nanoparticles on Plant Growth.

Melatonin and serotonin are well-known signaling molecules that mediate multiple physiological activities in plants, including stress defense, growth, development, and morphogenesis, but their underlying mechanisms have not yet been thoroughly elucidated. In this study, we investigated the roles of melatonin and serotonin in modulating plant growth and defense by integrating physiological and transcriptome analyses in Arabidopsis. Moderate concentrations of melatonin and serotonin did not affect primary root (PR) growth but markedly induced lateral root (LR) formation. Both melatonin and serotonin locally induced the expression of the cell-wall-remodeling-related genes LBD16 and XTR6, thereby inducing LR development. Our data support the idea that melatonin and serotonin lack any auxin-like activity. Treatment with 50 μM serotonin significantly improved PSII activity, and the transcriptome data supported this result. Melatonin and serotonin slightly affected glycolysis and the TCA cycle; however, they markedly regulated the catabolism of several key amino acids, thereby affecting carbon metabolism and energy metabolism. Melatonin and serotonin improved iron (Fe) deficiency tolerance by inducing Fe-responsive gene expression. Overall, our results from the physiological and transcriptome analyses reveal the roles of melatonin and serotonin in modulating plant growth and stress responses and provide insight into novel crop production strategies using these two phytoneurotransmitters.

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Comparative physiological responses and transcriptome analysis reveal the roles of melatonin and serotonin in regulating growth and metabolism in Arabidopsis

http://academic.oup.com/plphys/advance-article-pdf/doi/10.1093/plphys/kiab193/40080692/kiab193.pdf

2021 update on ATP-binding cassette (ABC) transporters: how they meet the needs of plants

Involvement of reactive oxygen species and auxin in serotonin-induced inhibition of primary root elongation.

cGMP is involved in Zn tolerance through the modulation of auxin redistribution in root tips

The ATP-binding cassette (ABC) F/GCN (general control non-derepressible) subfamily is a group of soluble ABC proteins that has two nucleotide binding domains (NBDs) but no transmembrane domains (TMDs). Previous study has indicated that ABCF3, also called GCN20/SCORD5, is involved in stress-associated protein translation control and defense responses to bacterial infection. Here, we show that ABCF3 regulates H2O2 uptake and endoplasmic reticulum (ER) stress responses in Arabidopsis. ABCF3 expressed mainly in leaves, stems, root tips, seeds, and anther. Analysis of abcf3 mutants and transgenic overexpressors (OX) of ABCF3 indicates that ABCF3 regulates H2O2 uptake. qRT-PCR analysis indicated that ABCF3 affects the expression of several aquaporin genes that were involved in H2O2 uptake in plants. In addition, abcf3 mutants exhibited enhanced sensitivity to ER stress and amino acid deprivation when challenged with ER stress inducers tunicamycin and amino acid synthesis inhibitor chlorsulfuron compared to wild type. Overexpression of AtABCF3 increases, whereas, abcf3 mutants depress the expression of ER stress-related genes. Taken together, these results indicated that ABCF3 regulates stress response by modulating aquaporin gene expression and ER stress responses.

Shuang Li

Papers

Involvement of reactive oxygen species and auxin in serotonin-induced inhibition of primary root elongation.

cGMP is involved in Zn tolerance through the modulation of auxin redistribution in root tips

ABCF3 regulates the expression of aquaporin genes and endoplasmic reticulum stress-related genes in Arabidopsis