ROS and calcium oscillations are required for polarized root hair growth

Polar localization and local translation of RHO-RELATED PROTEIN FROM PLANTS2 mRNAs promote root hair growth in Arabidopsis

Root hairs are tip-growing cells that anchor plants in the soil and are critical for water uptake, nutrient acquisition, and plant-environment interactions. While the molecular mechanisms that maintain the polar growth of root hairs through the asymmetric distribution of proteins, such as RHO-RELATED PROTEIN FROM PLANTS 2 (ROP2), have been described, it is unclear whether and how the transcripts encoding these tip-localized proteins are polarly localized and locally translated. Here, we demonstrated that ROP2 mRNA exhibits polar localization in Arabidopsis (Arabidopsis thaliana) root hairs. We showed that region VI (250-350 bp downstream of the stop codon) of the ROP2 3' untranslated region (UTR) is necessary for proper mRNA localization. Moreover, region VI-mediated ROP2 mRNA polar localization was required for local translation of ROP2 transcripts, contributing to the proper subcellular localization of ROP2. Region III (100-200 bp downstream of the stop codon) influenced the local translation of ROP2 mRNA. Phenotypic investigations demonstrated that both regions III and VI of the ROP2 3' UTR play crucial roles in modulating root hair growth. These findings help explain the local protein biosynthesis of ROP2, advancing our understanding of the regulatory mechanism and genetic basis of mRNA localization and local translation in plants.

Response of Arabidopsis thaliana to Flooding with Physical Flow

Flooding causes severe yield losses worldwide, making it urgent to enhance crop tolerance to this stress. Since natural flooding often involves physical flow, we hypothesized that the effects of submergence on plants could change when combined with physical flow. In this study, we analyzed the growth and transcriptome of Arabidopsis thaliana exposed to submergence or flooding with physical flow. Plants exposed to flooding with physical flow had smaller rosette diameters, especially at faster flow rates. Transcriptome analysis revealed that "defense response" transcripts were highly up-regulated in response to flooding with physical flow. In addition, up-regulation of transcripts encoding ROS-producing enzymes, SA synthesis, JA synthesis, and ethylene signaling was more pronounced under flooding with physical flow when compared to submergence. Although H2O2 accumulation changed in response to submergence or flooding with physical flow, it did not lead to lipid peroxidation, suggesting a role for ROS as signaling molecules under these conditions. Multiple regression analysis indicated possible links between rosette diameter under flooding with physical flow and the expression of Rbohs and SA synthesis transcripts. These findings suggest that pathogen defense responses, regulated by SA and ROS signaling, play crucial roles in plant responses to flooding with physical flow.

Mechanisms by Which Exogenous Substances Enhance Plant Salt Tolerance through the Modulation of Ion Membrane Transport and Reactive Oxygen Species Metabolism

Soil salinization is one of the major abiotic stresses affecting plant growth and development. Plant salt tolerance is controlled by complex metabolic pathways. Exploring effective methods and mechanisms to improve crop salt tolerance has been a key aspect of research on the utilization of saline soil. Exogenous substances, such as plant hormones and signal transduction substances, can regulate ion transmembrane transport and eliminate reactive oxygen species (ROS) to reduce salt stress damage by activating various metabolic processes. In this review, we summarize the mechanisms by which exogenous substances regulate ion transmembrane transport and ROS metabolism to improve plant salt tolerance. The molecular and physiological relationships among exogenous substances in maintaining the ion balance and enhancing ROS clearance are examined, and trends and research directions for the application of exogenous substances for improving plant salt tolerance are proposed.

CsWRKY11 cooperates with CsNPR1 to regulate SA-triggered leaf de-greening and reactive oxygen species burst in cucumber

Salicylic acid (SA) is a multi-functional phytohormone, regulating diverse processes of plant growth and development, especially triggering plant immune responses and initiating leaf senescence. However, the early SA signaling events remain elusive in most plant species apart from Arabidopsis, and even less is known about the multi-facet mechanism underlying SA-regulated processes. Here, we report the identification of a novel regulatory module in cucumber, CsNPR1-CsWRKY11, which mediates the regulation of SA-promoted leaf senescence and ROS burst. Our analyses demonstrate that under SA treatment, CsNPR1 recruits CsWRKY11 to bind to the promoter of CsWRKY11 to activate its expression, thus amplifying the primary SA signal. Then, CsWRKY11 cooperates with CsNPR1 to directly regulate the expression of both chlorophyll degradation and ROS biosynthesis related genes, thereby inducing leaf de-greening and ROS burst. Our study provides a solid line of evidence that CsNPR1 and CsWRKY11 constitute a key module in SA signaling pathway in cucumber, and gains an insight into the interconnected regulation of SA-triggered processes.

The plant cell wall-dynamic, strong, and adaptable-is a natural shapeshifter

Mythology is replete with good and evil shapeshifters, who, by definition, display great adaptability and assume many different forms-with several even turning themselves into trees. Cell walls certainly fit this definition as they can undergo subtle or dramatic changes in structure, assume many shapes, and perform many functions. In this review, we cover the evolution of knowledge of the structures, biosynthesis, and functions of the 5 major cell wall polymer types that range from deceptively simple to fiendishly complex. Along the way, we recognize some of the colorful historical figures who shaped cell wall research over the past 100 years. The shapeshifter analogy emerges more clearly as we examine the evolving proposals for how cell walls are constructed to allow growth while remaining strong, the complex signaling involved in maintaining cell wall integrity and defense against disease, and the ways cell walls adapt as they progress from birth, through growth to maturation, and in the end, often function long after cell death. We predict the next century of progress will include deciphering cell type-specific wall polymers; regulation at all levels of polymer production, crosslinks, and architecture; and how walls respond to developmental and environmental signals to drive plant success in diverse environments.

Bio-positive effects of ionizing radiation on pollen: The role of ROS

The concept of 'hormesis' is defined as a dose-response relationship whereby low doses of various toxic substances or physical stressors trigger bio-positive effects in diverse biological systems, whereas high doses cause inhibition of cellular performance (e.g. growth, viability). The two-sided phenomenon of specific low-dose stimulation and high-dose inhibition imposed by a 'hormetic-factor' has been well documented in toxicology and pharmacology. Multitudinous factors have been identified that correspondingly cause hormetic effects in diverse taxa of animals, fungi, and plants. This study particularly aims to elucidate the molecular basis for stimulatory implications of ionizing radiation (IR) on plant male gametophytes (pollen). Beyond that, this analysis impacts general research on cell growth, plant breeding, radiation protection, and, in a wider sense, medical treatment. For this purpose, IR-related data were surveyed and discussed in connection with the present knowledge about pollen physiology. It is concluded that IR-induced reactive oxygen species (ROS) have a key role here. Moreover, it is hypothesized that IR-exposure shifts the ratio between diverse types of ROS in the cell. The interrelation between ROS, intracellular Ca2+-gradient, NADPH oxidases, ROS-scavengers, actin dynamics, and cell wall properties are most probably involved in IR-hormesis of pollen germination and tube growth. Modulation of gene expression, phytohormone signalling, and cellular antioxidant capacity are also implicated in IR-hormesis.

The role of lipid-modified proteins in cell wall synthesis and signaling

The plant cell wall is a complex and dynamic extracellular matrix. Plant primary cell walls are the first line of defense against pathogens and regulate cell expansion. Specialized cells deposit a secondary cell wall that provides support and permits water transport. The composition and organization of the cell wall varies between cell types and species, contributing to the extensibility, stiffness, and hydrophobicity required for its proper function. Recently, many of the proteins involved in the biosynthesis, maintenance, and remodeling of the cell wall have been identified as being post-translationally modified with lipids. These modifications exhibit diverse structures and attach to proteins at different sites, which defines the specific role played by each lipid modification. The introduction of relatively hydrophobic lipid moieties promotes the interaction of proteins with membranes and can act as sorting signals, allowing targeted delivery to the plasma membrane regions and secretion into the apoplast. Disruption of lipid modification results in aberrant deposition of cell wall components and defective cell wall remodeling in response to stresses, demonstrating the essential nature of these modifications. Although much is known about which proteins bear lipid modifications, many questions remain regarding the contribution of lipid-driven membrane domain localization and lipid heterogeneity to protein function in cell wall metabolism. In this update, we highlight the contribution of lipid modifications to proteins involved in the formation and maintenance of plant cell walls, with a focus on the addition of glycosylphosphatidylinositol anchors, N-myristoylation, prenylation, and S-acylation.

OsRbohI Regulates Rice Growth and Development via Jasmonic Acid Signalling

Reactive oxygen species (ROS) are highly reactive molecules, generated by nicotinamide adenine dinucleotide phosphate oxidases encoded by respiratory burst oxidase homologs. The functions of the OsRbohs gene family in rice are diverse and poorly understood. OsRbohI was recently identified as a newly evolved gene in the rice OsRbohs gene family. However, the function of OsRbohI in regulating rice growth is not yet reported. In this study, our results indicate that knockout (KO) OsRbohI mutants showed significantly shorter shoot and primary roots, along with lower ROS content than the control lines, whereas the overexpression (OE) lines displayed contrasting results. Further experiments showed that the abnormal length of the shoot and root is mainly caused by altered cell size. These results indicate that OsRbohI regulates rice shoot and root growth through the ROS signal. More importantly, RNA-seq analysis and jasmonic acid (JA) treatment demonstrated that OsRbohI regulates rice growth via the JA synthesis and signaling pathways. Compared with the control, the results showed that the KO mutants were more sensitive to JA, whereas the OE lines were less sensitive to JA. Collectively, our results reveal a novel pathway in which OsRbohI regulates rice growth and development by affecting their ROS homeostasis through JA synthesis and signaling pathway.

Cadmium-induced oxidative stress responses and acclimation in plants require fine-tuning of redox biology at subcellular level

Cadmium (Cd) is one of the most toxic compounds released into our environment and is harmful to human health, urging the need to remediate Cd-polluted soils. To this end, it is important to increase our insight into the molecular mechanisms underlying Cd stress responses in plants, ultimately leading to acclimation, and to develop novel strategies for economic validation of these soils. Albeit its non-redox-active nature, Cd causes a cellular oxidative challenge, which is a crucial determinant in the onset of diverse signalling cascades required for long-term acclimation and survival of Cd-exposed plants. Although it is well known that Cd affects reactive oxygen species (ROS) production and scavenging, the contribution of individual organelles to Cd-induced oxidative stress responses is less well studied. Here, we provide an overview of the current information on Cd-induced organellar responses with special attention to redox biology. We propose that an integration of organellar ROS signals with other signalling pathways is essential to finetune plant acclimation to Cd stress.

Review of the Mechanisms by Which Transcription Factors and Exogenous Substances Regulate ROS Metabolism under Abiotic Stress

Reactive oxygen species (ROS) are signaling molecules that regulate many biological processes in plants. However, excess ROS induced by biotic and abiotic stresses can destroy biological macromolecules and cause oxidative damage to plants. As the global environment continues to deteriorate, plants inevitably experience abiotic stress. Therefore, in-depth exploration of ROS metabolism and an improved understanding of its regulatory mechanisms are of great importance for regulating cultivated plant growth and developing cultivars that are resilient to abiotic stresses. This review presents current research on the generation and scavenging of ROS in plants and summarizes recent progress in elucidating transcription factor-mediated regulation of ROS metabolism. Most importantly, the effects of applying exogenous substances on ROS metabolism and the potential regulatory mechanisms at play under abiotic stress are summarized. Given the important role of ROS in plants and other organisms, our findings provide insights for optimizing cultivation patterns and for improving plant stress tolerance and growth regulation.