Involvement of protein phosphorylation in water stress-induced antioxidant defense in maize leaves

Peroxiredoxins and Redox Signaling in Plants

SIGNIFICANCE

Peroxiredoxins (Prxs) are thiol peroxidases with multiple functions in the antioxidant defense and redox signaling network of the cell. Our progressing understanding assigns both local and global significance to plant Prxs, which are grouped in four Prx types. In plants they are localized to the cytosol, mitochondrion, plastid, and nucleus. Antioxidant defense is fundamentally connected to redox signaling, cellular communication, and acclimation. The thiol-disulfide network is central part of the stress sensing and processing response and integrates information input with redox regulation. Recent Advances: Prxs function both as redox sensory system within the network and redox-dependent interactors. The processes directly or indirectly targeted by Prxs include gene expression, post-transcriptional reactions, including translation, post-translational regulation, and switching or tuning of metabolic pathways, and other cell activities. The most advanced knowledge is available for the chloroplast 2-CysPrx wherein recently a solid interactome has been defined. An in silico analysis of protein structure and coexpression reinforces new insights into the 2-CysPrx functionality.

CRITICAL ISSUES

Up to now, Prxs often have been investigated for local properties of enzyme activity. In vitro and ex vivo work with mutants will reveal the ability of Prxs to interfere with multiple cellular components, including crosstalk with Ca²⁺-linked signaling pathways, hormone signaling, and protein homeostasis.

FUTURE DIRECTIONS

Complementation of the Prxs knockout lines with variants that mimic specific states, namely devoid of peroxidase activity, lacking the oligomerization ability, resembling the hyperoxidized decamer, or with truncated C-terminus, should allow dissecting the roles as thiol peroxidase, oxidant, interaction partner, and chaperone. Antioxid. Redox Signal. 28, 609-624.

Novel aspects of grapevine response to phytoplasma infection investigated by a proteomic and phospho-proteomic approach with data integration into functional networks

BACKGROUND

Translational and post-translational protein modifications play a key role in the response of plants to pathogen infection. Among the latter, phosphorylation is critical in modulating protein structure, localization and interaction with other partners. In this work, we used a multiplex staining approach with 2D gels to study quantitative changes in the proteome and phosphoproteome of Flavescence dorée-affected and recovered 'Barbera' grapevines, compared to healthy plants.

RESULTS

We identified 48 proteins that differentially changed in abundance, phosphorylation, or both in response to Flavescence dorée phytoplasma infection. Most of them did not show any significant difference in recovered plants, which, by contrast, were characterized by changes in abundance, phosphorylation, or both for 17 proteins not detected in infected plants. Some enzymes involved in the antioxidant response that were up-regulated in infected plants, such as isocitrate dehydrogenase and glutathione S-transferase, returned to healthy-state levels in recovered plants. Others belonging to the same functional category were even down-regulated in recovered plants (oxidoreductase GLYR1 and ascorbate peroxidase). Our proteomic approach thus agreed with previously published biochemical and RT-qPCR data which reported down-regulation of scavenging enzymes and accumulation of H2O2 in recovered plants, possibly suggesting a role for this molecule in remission from infection. Fifteen differentially phosphorylated proteins (| ratio | > 2, p < 0.05) were identified in infected compared to healthy plants, including proteins involved in photosynthesis, response to stress and the antioxidant system. Many were not differentially phosphorylated in recovered compared to healthy plants, pointing to their specific role in responding to infection, followed by a return to a steady-state phosphorylation level after remission of symptoms. Gene ontology (GO) enrichment and statistical analysis showed that the general main category "response to stimulus" was over-represented in both infected and recovered plants but, in the latter, the specific child category "response to biotic stimulus" was no longer found, suggesting a return to steady-state levels for those proteins specifically required for defence against pathogens.

CONCLUSIONS

Proteomic data were integrated into biological networks and their interactions were represented through a hypothetical model, showing the effects of protein modulation on primary metabolic ways and related secondary pathways. By following a multiplex-staining approach, we obtained new data on grapevine proteome pathways that specifically change at the phosphorylation level during phytoplasma infection and following recovery, focusing for the first time on phosphoproteome changes during pathogen infection in this host.

60 years of development of the journal of integrative plant biology

In celebration of JIPB's 60(th) anniversary, this paper summarizes and reviews the development process of the journal. To start, we offer our heartfelt thanks to JIPB's pioneer Editors-in-Chief who helped get the journal off the ground and make it successful. Academic achievement is the soul of academic journals, and this paper summarizes JIPB's course of academic development by analyzing it in four stages: the first two stages are mostly qualitative analyses, and the latter two stages are dedicated to quantitative analyses. Most-cited papers were statistically analyzed. Improvements in editing, publication, distribution and online accessibility--which are detailed in this paper--contribute to JIPB's sustainable development. In addition, JIPB's evaluation index and awards are provided with accompanying pictures. At the end of the paper, JIPB's milestones are listed chronologically. We believe that JIPB's development, from a national journal to an international one, parallels the development of the Chinese plant sciences.

Differential response of young and adult leaves to herbicide 2,4-dichlorophenoxyacetic acid in pea plants: role of reactive oxygen species

In this work the differential response of adult and young leaves from pea (Pisum sativum L.) plants to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) (23 mm) applied by foliar spraying was investigated. The concentration of 2,4-D (23 mm) and the time of treatment (72 h) were previously optimized in order to visualize its toxic effects on pea plants. Under these conditions, the herbicide induced severe disturbances in mesophyll cells structure and proliferation of vascular tissue in young leaves and increased acyl-CoA oxidase (ACX), xanthine oxidase (XOD) and lipoxygenase (LOX) activities in young leaves, and only ACX and LOX in adult leaves. This situation produced reactive oxygen species (ROS) over-accumulation favoured by the absence of significant changes in the enzymatic antioxidants, giving rise to oxidative damages to proteins and membrane lipids. An increase of ethylene took place in both young and adult leaves and the induction of genes encoding the stress proteins, PRP4A and HSP 71,2, was observed mainly in young leaves. These results suggest that ROS overproduction is a key factor in the effect of high concentrations of 2,4-D, and ROS can trigger a differential response in young and adult leaves, either epinasty development in young leaves or senescence processes in adult tissues.