The NADPH-oxidase LsRbohC1 plays a role in lettuce (Lactuca sativa) seed germination

Environmental risk substances in soil on seed germination: Chemical species, inhibition performance, and mechanisms

Nowadays, numerous environmental risk substances in soil worldwide have exhibited serious germination inhibition of crop seeds, posing a threat to food supply and security. This review provides a comprehensive summary and discussion of the inhibitory effects of environmental risk substances on seed germination, encompassing heavy metals, microplastics, petroleum hydrocarbons, salinity, phenols, essential oil, agricultural waste, antibiotics, etc. The impacts of species, concentrations, and particle sizes of various environmental risk substances are critically investigated. Furthermore, three primary inhibition mechanisms of environmental risk substances are elucidated: hindering water absorption, inducing oxidative damage, and damaging seed cells/organelles/cell membranes. To address these negative impacts, diverse effective coping measures such as biochar/compost addition, biological remediation, seed priming, coating, and genetic modification are proposed. In brief, this study systematically analyzes the negative effects of environmental risk substances on seed germination, and provides a basis for the comprehensive understanding and future implementation of efficient treatments to address this significant challenge and ensure food security and human survival.

Evolutionary Analysis of Respiratory Burst Oxidase Homolog (RBOH) Genes in Plants and Characterization of ZmRBOHs

The respiratory burst oxidase homolog (RBOH), as the key producer of reactive oxygen species (ROS), plays an essential role in plant development. In this study, a bioinformatic analysis was performed on 22 plant species, and 181 RBOH homologues were identified. A typical RBOH family was identified only in terrestrial plants, and the number of RBOHs increased from non-angiosperms to angiosperms. Whole genome duplication (WGD)/segmental duplication played a key role in RBOH gene family expansion. Amino acid numbers of 181 RBOHs ranged from 98 to 1461, and the encoded proteins had molecular weights from 11.1 to 163.6 kDa, respectively. All plant RBOHs contained a conserved NADPH_Ox domain, while some of them lacked the FAD_binding_8 domain. Plant RBOHs were classified into five main subgroups by phylogenetic analysis. Most RBOH members in the same subgroup showed conservation in both motif distribution and gene structure composition. Fifteen ZmRBOHs were identified in maize genome and were positioned in eight maize chromosomes. A total of three pairs of orthologous genes were found in maize, including ZmRBOH6/ZmRBOH8, ZmRBOH4/ZmRBOH10 and ZmRBOH15/ZmRBOH2. A Ka/Ks calculation confirmed that purifying selection was the main driving force in their evolution. ZmRBOHs had typical conserved domains and similar protein structures. cis-element analyses together with the expression profiles of the ZmRBOH genes in various tissues and stages of development suggested that ZmRBOH was involved in distinct biological processes and stress responses. Based on the RNA-Seq data and qRT-PCR analysis, the transcriptional response of ZmRBOH genes was examined under various abiotic stresses, and most of ZmRBOH genes were up-regulated by cold stress. These findings provide valuable information for further revealing the biological roles of ZmRBOH genes in plant development and abiotic stress responses.

Bactericidal activity of Ag4V2O7/β-AgVO3 heterostructures against antibiotic-resistant Klebsiella pneumoniae

Although Ag-based materials are efficient against antibiotic-resistant bacteria, their high toxicity to living organisms represents a major challenge for obtaining useful products. In this work, we report the bactericidal activity of Ag₄V₂O₇/β-AgVO₃ heterostructures, which proved to be effective against Klebsiella pneumoniae (ATCC 1706, a standard strain; A54970, a multidrug-resistant carbapenemase (KPC)-producing strain; A34057, a multidrug-resistant strain capable of producing extended spectrum beta-lactamases (ESBL); and a community-isolated strain, A58240) at minimum inhibitory concentrations (MIC) as low as 62.5 μg/mL. This activity is higher than that reported for the individual silver vanadates (Ag₄V₂O₇ or β-AgVO₃) owing to the synergistic interactions between both semiconductors. However, the most efficient heterostructure was found to be toxic to mouse 3 T3 fibroblasts and to L. sativa and C. sativus seeds, as indicated by MTT ((4,5 - dimethylthiazol -2yl) 2,5 -diphenylbromide), neutral red assays and germination index measurements. The antimicrobial, phytotoxic and cytotoxic activities were all associated with an efficient generation of reactive oxygen species (ROS) in the heterostructure, especially OH and O₂^- radicals. The ROS production by Ag₄V₂O₇/β-AgVO₃ heterostructures was measured through photodegradation studies with Rhodamine B. While the bactericidal activity of the heterostructures is promising, especially when compared to Ag-based materials, their use in practical applications will require encapsulation either to avoid leaching or to mitigate their toxicity to humans, animals and plants.

Production of reactive oxygen species by PuRBOHF is critical for stone cell development in pear fruit

The production of reactive oxygen species (ROS) by NADPH oxidase, which is also referred to as respiratory burst oxidase homolog (RBOH), affects several processes in plants. However, the role of RBOHs in cell wall lignification is not well understood. In this study, we show that PuRBOHF, an RBOH isoform, plays an important role in secondary wall formation in pear stone cells. ROS were closely associated with lignin deposition and stone cell formation according to microscopy data. In addition, according to the results of an in situ hybridization analysis, the stage-specific expression of PuRBOHF was higher in stone cells than in cells of other flesh tissues. Inhibitors of RBOH activity suppressed ROS accumulation and stone cell lignification in pear fruit. Moreover, transient overexpression of PuRBOHF caused significant changes in the amount of ROS and lignin that accumulated in pear fruit and flesh calli. We further showed that PuMYB169 regulates PuRBOHF expression, while PuRBOHF-derived ROS induces the transcription of PuPOD2 and PuLAC2. The findings of this study indicate that PuRBOHF-mediated ROS production, which is regulated by a lignin-related transcriptional network, is essential for monolignol polymerization and stone cell formation in pear fruit.

Oxidative signalling in seed germination and early seedling growth: an emerging role for ROS trafficking and inter-organelle communication

Underground early development of higher plants includes two distinct developmental processes, seed germination and then skotomorphogenesis, a mechanism which favours elongation of the hypocotyl and helps the seedling to find light. Interestingly, both processes, which are regulated by plant hormones, have been shown to depend on reactive oxygen species metabolism and to be related to mitochondrial retrograde signalling. Here we review the recent outcomes in this field of research and highlight the emerging role of ROS communication between organelles and cell compartments. We point out the role of mitochondria as an environmental and developmental sensor organelle that regulates ROS homeostasis and downstream events and we propose future directions of research that should help better understanding the roles of ROS in germination and seedling emergence.

Roles of Reactive Oxygen Species and Mitochondria in Seed Germination

Seed germination is crucial for the life cycle of plants and maximum crop production. This critical developmental step is regulated by diverse endogenous [hormones, reactive oxygen species (ROS)] and exogenous (light, temperature) factors. Reactive oxygen species promote the release of seed dormancy by biomolecules oxidation, testa weakening and endosperm decay. Reactive oxygen species modulate metabolic and hormone signaling pathways that induce and maintain seed dormancy and germination. Endosperm provides nutrients and senses environmental signals to regulate the growth of the embryo by secreting timely signals. The growing energy demand of the developing embryo and endosperm is fulfilled by functional mitochondria. Mitochondrial matrix-localized heat shock protein GhHSP24.7 controls seed germination in a temperature-dependent manner. In this review, we summarize comprehensive view of biochemical and molecular mechanisms, which coordinately control seed germination. We also discuss that the accurate and optimized coordination of ROS, mitochondria, heat shock proteins is required to permit testa rupture and subsequent germination.