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Plant plasma membrane H+-ATPase is a transport protein that is generally located on the plasma membrane and generates energy by hydrolyzing adenosine triphosphate (ATP) to pump hydrogen ions (H+) in the cytoplasm out of the cell against a concentration gradient. The plasma membrane H+-ATPases in plants are encoded by a multigene family and potentially play a fundamental role in regulating plant responses to various abiotic stresses, thus contributing to plant adaptation under adverse conditions. To understand the characteristics of the plasma membrane H+-ATPase family in peach (Prunus persica), this study analyzed the plasma membrane H+-ATPase family genes in peach. The results showed that there were 27 members of the plasma membrane H+-ATPase family in peach with amino acid sequences ranging from 943 to 1327. Subcellular localization showed that 23 of the 27 members were located on the cell membrane, and the phylogenetic tree analysis indicated that peach plasma membrane H+-ATPase members were divided into five groups. There were four genes with tandem repeat relationships, and six plasma membrane H+-ATPase genes were differentially expressed after 5 days of flooding and under non-flooding conditions based on the RNA-seq and RT-qPCR analyses. This study also investigated the characteristics and possible functions of the plasma membrane H+-ATPase family members in peach. The results provide theoretical support for further studies on their biological functions in peach. [ABSTRACT FROM AUTHOR]

High concentrations of sodium (Na+), chloride (Cl−), calcium (Ca2+), and sulphate (SO42−) are frequently found in saline soils. Crop plants cannot successfully develop and produce because salt stress impairs the uptake of Ca2+, potassium (K+), and water into plant cells. Different intracellular and extracellular ionic concentrations change with salinity, including those of Ca2+, K+, and protons. These cations serve as stress signaling molecules in addition to being essential for ionic homeostasis and nutrition. Maintaining an appropriate K+:Na+ ratio is one crucial plant mechanism for salt tolerance, which is a complicated trait. Another important mechanism is the ability for fast extrusion of Na+ from the cytosol. Ca2+ is established as a ubiquitous secondary messenger, which transmits various stress signals into metabolic alterations that cause adaptive responses. When plants are under stress, the cytosolic-free Ca2+ concentration can rise to 10 times or more from its resting level of 50–100 nanomolar. Reactive oxygen species (ROS) are linked to the Ca2+ alterations and are produced by stress. Depending on the type, frequency, and intensity of the stress, the cytosolic Ca2+ signals oscillate, are transient, or persist for a longer period and exhibit specific "signatures". Both the influx and efflux of Ca2+ affect the length and amplitude of the signal. According to several reports, under stress Ca2+ alterations can occur not only in the cytoplasm of the cell but also in the cell walls, nucleus, and other cell organelles and the Ca2+ waves propagate through the whole plant. Here, we will focus on how wheat and other important crops absorb Na+, K+, and Cl− when plants are under salt stress, as well as how Ca2+, K+, and pH cause intracellular signaling and homeostasis. Similar mechanisms in the model plant Arabidopsis will also be considered. Knowledge of these processes is important for understanding how plants react to salinity stress and for the development of tolerant crops. [ABSTRACT FROM AUTHOR]

Upon storage, seeds inevitably age and lose their viability over time, which determines their longevity. Longevity correlates with successful seed germination and enhancing this trait is of fundamental importance for long-term seed storage (germplasm conservation) and crop improvement. Seed longevity is governed by a complex interplay between genetic factors and environmental conditions experienced during seed development and after-ripening that will shape seed physiology. Several factors have been associated with seed ageing such as oxidative stress responses, DNA repair enzymes, and composition of seed layers. Phytohormones, mainly abscisic acid, auxins, and gibberellins, have also emerged as prominent endogenous regulators of seed longevity, and their study has provided new regulators of longevity. Gaining a thorough understanding of how hormonal signalling genes and pathways are integrated with downstream mechanisms related to seed longevity is essential for formulating strategies aimed at preserving seed quality and viability. A relevant aspect related to research in seed longevity is the existence of significant differences between results depending on the seed equilibrium relative humidity conditions used to study seed ageing. Hence, this review delves into the genetic, environmental and experimental factors affecting seed ageing and longevity, with a particular focus on their hormonal regulation. We also provide gene network models underlying hormone signalling aimed to help visualize their integration into seed longevity and ageing. We believe that the format used to present the information bolsters its value as a resource to support seed longevity research for seed conservation and crop improvement. [ABSTRACT FROM AUTHOR]

We have analyzed the kinetics of seed germination of the model plant Arabidopsis thaliana after γ‑irradiation at doses of 50, 100, and 150 Gy. The following lines were selected as study objects: abi3-8 with a mutation in the ABI3 gene and with reduced sensitivity to the natural form of abscisic acid and the aba3-1 genotype with a mutation in the ABA3 gene and a reduced level of the endogenous abscisic acid. Wild type Col-8 was used as a control. To study the effect of γ-radiation on various aspects of seed germination (germinability, germination time and rate, synchrony of germination, etc.), the germination kinetics was assessed using the Germinationmetrics package for the R programming environment. Control and irradiated seeds (radiation source 60Co) were grown on half-strength Murashige–Skoog medium under controlled conditions. Germination was assessed during the first six days after transfer to the phytotron by the rupture of the endosperm and the appearance of the root. In total, three independent experiments were carried out with three biological replications in each. A more pronounced effect of γ-radiation at a dose of 150 Gy on all studied genotypes was noted. Germination clustering showed that the distribution of the percentage of seed germination by day depends more on the genotype than on the dose of exposure. The best indicators of germination, the speed and time interval between germination of 10 to 90% of seeds, were noted for non-irradiated seeds of the abi3-8 line. The results obtained and a comparative analysis with previously published data suggest that the assessment of germination kinetics using the Germinationmetrics package for R is a clear and quite informative tool for studying the effect of ionizing radiation and other abiotic factors on various aspects of seed germination. [ABSTRACT FROM AUTHOR]

Basic features of seed dormancy are illustrated. The seed overall regulatory network governs seed metabolism and development, and it is coordinated by plant hormones. A functional model focused on abscisic acid (ABA), the foremost plant hormone in dormancy, is used as a framework to critically discuss the literature. Gibberellins (GAs) have a main role in germination, and the ABA–GAs balance is a typical feature of the seed state: ABA dominates during dormancy and GAs prevail through germination. Thus, the literature converges toward envisaging the development switch between dormancy and germination as represented by the ABA/GAs ratio. The ABA–GAs antagonism is based on mutual inhibition, a feature of the regulatory network architecture that characterizes development trajectories based on a regulatory circuit with a bistable switch. Properties of such kind of regulatory architecture are introduced step by step, and it is shown that seed development—toward either dormancy or germination—is more properly represented by a tristable regulatory circuit, whose intermediate metastable states ultimately take one or the other development trajectory. Although the ABA/GAs ratio can conveniently represent the state of the seed overall regulatory network along the seed development trajectory, specific (unknown) dormancy factors are required to determine the development trajectory. The development landscape is shown to provide a well-suited representation of seed states travelling along developmental trajectories, particularly when the states are envisioned as regulatory circuits. Looking at seed dormancy in terms of regulatory circuits and development landscapes offers a valuable perspective to improve our understanding of this biological phenomenon. [ABSTRACT FROM AUTHOR]

Summary: Increasing drought phenomena pose a serious threat to agricultural productivity. Although plants have multiple ways to respond to the complexity of drought stress, the underlying mechanisms of stress sensing and signaling remain unclear. The role of the vasculature, in particular the phloem, in facilitating inter‐organ communication is critical and poorly understood.Combining genetic, proteomic and physiological approaches, we investigated the role of AtMC3, a phloem‐specific member of the metacaspase family, in osmotic stress responses in Arabidopsis thaliana. Analyses of the proteome in plants with altered AtMC3 levels revealed differential abundance of proteins related to osmotic stress pointing into a role of the protein in water‐stress‐related responses.Overexpression of AtMC3 conferred drought tolerance by enhancing the differentiation of specific vascular tissues and maintaining higher levels of vascular‐mediated transportation, while plants lacking the protein showed an impaired response to drought and inability to respond effectively to the hormone abscisic acid.Overall, our data highlight the importance of AtMC3 and vascular plasticity in fine‐tuning early drought responses at the whole plant level without affecting growth or yield. [ABSTRACT FROM AUTHOR]

Seed germination is a complex process involving several stages, starting with the imbibition of water and ending with the emergence of the radicle. In the current study, we address the observation of an unexpected pH shift during the imbibition of maize grains. We used direct pH measurements of soak water, the pH indicator methyl red, and anatomical analysis to shed light on the acidification associated with maize (Zea mays L.) germination, a largely overlooked phenomenon. Our work shows that acidification during imbibition of maize grains is a two-step process: (i) early, rapid acidification (pH values up to 4.4), in which protons stored in the (dead) pericarp/testa are mobilised and rapidly diffuse into the surrounding medium, and (ii) late, delayed acidification (pH values just below 6), starting hours after contact of grains with water, representing an active transport process caused by living cells of the seed. We discuss the physiological mechanisms and ecological relevance of environmental acidification during maize grain germination. [ABSTRACT FROM AUTHOR]

Phytopathogens are well known for their devastating activity that causes worldwide significant crop losses. However, their exploitation for crop welfare is relatively unknown. Here, we show that the microbial volatile organic compound (mVOC) profile of the bacterial phytopathogen, Erwinia amylovora, enhances Arabidopsis thaliana shoot and root growth. GC-MS head-space analyses revealed the presence of typical microbial volatiles, including 1-nonanol and 1-dodecanol. E. amylovora mVOCs triggered early signaling events including plasma transmembrane potential Vm depolarization, cytosolic Ca2+ fluctuation, K+-gated channel activity, and reactive oxygen species (ROS) and nitric oxide (NO) burst from few minutes to 16 h upon exposure. These early events were followed by the modulation of the expression of genes involved in plant growth and defense responses and responsive to phytohormones, including abscisic acid, gibberellin, and auxin (including the efflux carriers PIN1 and PIN3). When tested, synthetic 1-nonanol and 1-dodecanol induced root growth and modulated genes coding for ROS. Our results show that E. amylovora mVOCs affect A. thaliana growth through a cascade of early and late signaling events that involve phytohormones and ROS. [ABSTRACT FROM AUTHOR]

Astronium fraxinifolium Schott (Anacardiaceae), also known as a 'gonçalo-alves', is a tree of the American tropics, with distribution in Mexico, part of Central America, Argentina, Bolivia, Brazil and Paraguay. In Brazil it is an endangered species that occurs in the Cerrado, Caatinga and in the Amazon biomes. In support of ex situ conservation, this work aimed to study two accessions with different longevity (p50) of A. fraxinifolium collected from two different geographic regions, and to evaluate the transcriptome during aging of the seeds in order to identify genes related to seed longevity. Artificial ageing was performed at a constant temperature of 45 °C and 60% relative humidity. RNA was extracted from 100 embryonic axes exposed to control and aging conditions for 21 days. The transcriptome analysis revealed differentially expressed genes such as Late Embryogenesis Abundant (LEA) genes, genes involved in the photosystem, glycine rich protein (GRP) genes, and several transcription factors associated with embryo development and ubiquitin-conjugating enzymes. Thus, these results contribute to understanding which genes play a role in seed ageing, and may serve as a basis for future functional characterization of the seed aging process in A. fraxinifolium. [ABSTRACT FROM AUTHOR]

Different environmental and developmental cues involve low oxygen conditions, particularly those associated to abiotic stress conditions. It is widely accepted that plant responses to low oxygen conditions are mainly regulated by ethylene (ET). However, interaction with other hormonal signaling pathways as gibberellins (GAs), auxin (IAA), or nitric oxide (NO) has been well-documented. In this network of interactions, abscisic acid (ABA) has always been present and regarded to as a negative regulator of the development of morphological adaptations to soil flooding: hyponastic growth, adventitious root emergence, or formation of secondary aerenchyma in different plant species. However, recent evidence points toward a positive role of this plant hormone on the modulation of plant responses to hypoxia and, more importantly, on the ability to recover during the post-hypoxic period. In this work, the involvement of ABA as an emerging regulator of plant responses to low oxygen conditions alone or in interaction with other hormones is reviewed and discussed. [ABSTRACT FROM AUTHOR]

Soil flooding is a compound abiotic stress that alters soil properties and limits atmospheric gas diffusion (O2 and CO2) to the roots. The involvement of abscisic acid (ABA) in the regulation of soil flooding-specific genetic and metabolic responses has been scarcely studied despite its key importance as regulator in other abiotic stress conditions. To attain this objective, wild type and ABA-deficient tomatoes were subjected to short-term (24 h) soil waterlogging. After this period, gas exchange parameters were reduced in the wild type but not in ABA-deficient plants that always had higher E and g s . Transcript and metabolite alterations were more intense in waterlogged tissues, with genotype-specific variations. Waterlogging reduced the ABA levels in the roots while inducing PYR/PYL/RCAR ABA receptors and ABA-dependent transcription factor transcripts, of which induction was less pronounced in the ABA-deficient genotype. Ethylene/O2-dependent genetic responses (ERFVIIs, plant anoxia survival responses, and genes involved in the N-degron pathway) were induced in hypoxic tissues independently of the genotype. Interestingly, genes encoding a nitrate reductase and a phytoglobin involved in NO biosynthesis and scavenging and ERFVII stability were induced in waterlogged tissues, but to a lower extent in ABA-deficient tomato. At the metabolic level, flooding-induced accumulation of Ala was enhanced in ABA-deficient lines following a differential accumulation of Glu and Asp in both hypoxic and aerated tissues, supporting their involvement as sources of oxalacetate to feed the tricarboxylic acid cycle in waterlogged tissues and constituting a potential advantage upon long periods of soil waterlogging. The promoter analysis of upregulated genes indicated that the production of oxalacetate from Asp via Asp oxidase, energy processes such as acetyl-CoA, ATP, and starch biosynthesis, and the lignification process were likely subjected to ABA regulation. Taken together, these data indicate that ABA depletion in waterlogged tissues acts as a positive signal, inducing several specific genetic and metabolic responses to soil flooding. [ABSTRACT FROM AUTHOR]

Plant height (PH) is closely associated with yield-related traits and environmental adaptation. Seven pairs of near-isogenic lines (NILs) targeting four QTL on 3AL, 4BL, 4AS, and 7AL wheat chromosome arms were assessed for PH and four yield-related traits including yield per plant (Y/P), grain number per spike (G/S), thousand kernel weight (TKW), and biomass per plant (B/P). Significant differences were observed in the NIL pairs for the measured traits. NIL pairs targeting the 3AL QTL differed significantly in PH, G/S, and TKW; NILs targeting the 4BL QTL differed significantly in PH, Y/P, and B/P; NIL pairs targeting the 4AS QTL differed significantly in all the traits; and NIL pairs targeting the 7AL QTL differed significantly in PH. A 90 K SNP genotyping assay of the NILs detected nineteen SNPs associated with fourteen functional genes. Among them, eight candidate genes are related to Rht proteins, four genes are related to hormone pathways and two genes are related to carbohydrate synthesis and transport. By searching the interval marker physical positions, it was found that the four targeted QTL in this study overlapped with eight previously reported QTL for PH, TKW, biomass, and yield. Correlation analysis revealed that PH significantly and positively correlated with B/P and G/S. The SNP and candidate gene information is potentially useful for marker-assisted selection in breeding programs, and the four targeted QTL are proved to be critical genomic regions controlling the investigated agronomic traits, which can be further fine mapped to identify the underlying genes. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) plays versatile functions in regulating plant development and tolerance to various biotic and abiotic stresses. Towards elucidating the functions of one of the ABA receptors (ABARs) in rice, OsPYL10 was cloned from drought tolerant rice cv. Nagina 22 and was overexpressed under stress inducible RD29A promoter in a mega rice variety MTU1010 by using Agrobacterium mediated genetic transformation. Four single copy transgenic lines selected based on Southern blot analysis were used for physiological and molecular analysis. PYL10 receptor appears to regulate its ligand ABA accumulation as PYL10 overexpressing transgenics accumulated 2–3.3-fold higher levels of ABA than that of WT in flag leaf at anthesis under non-stress conditions. The enhanced accumulation of ABA was associated with enhanced expression of genes for ABA biosynthesis viz., ZEP1 , NCED1 , NCED2 , NCED3 , and NCED4 in transgenics than in WT plants. At seedling stage, PYL10 transgenics showed significantly higher survival rate under cold stress as compared with WT plants. qRT-PCR analysis showed that expression levels of cold responsive genes viz., DREB1F , MYB3R2 , TPP1 , COR410 , DEHYDRIN , and LEA3 were significantly higher in PYL10 overexpressing transgenic lines as compared to WT plants under cold stress. PYL10 transgenic and WT plants grown in the same pot were subjected to -80 kPa drought stress and recovery treatments at vegetative and reproductive stages. At vegetative stage drought stress, three overexpressing lines showed significantly higher grain yield (40–58%) and at reproductive stage drought stress one of these overexpression lines showed two-fold higher grain yield than that of WT plants. Excised leaf water loss analysis showed that PYL10 transgenic lost about 20% less water than WT plants. At reproductive stage, OsPYL10 transgenic maintained higher RWC, membrane stability index, chlorophyll content, and accumulated lower amount of MDA and H2O2 as compared with WT plants. qRT-PCR analysis showed that expression levels of RAB16 , Dehydrin , LEA3 , and ABA45 were higher in PYL10 transgenics as compared with WT plants under drought stress. Thus, overall results showed that OsPYL10 overexpression has potential to improve both drought and cold stress tolerance of indica rice. [ABSTRACT FROM AUTHOR]

Spermidine is a polyamine present in eukaryotes with essential functions in protein synthesis. At high concentrations spermidine and norspermidine inhibit growth by unknown mechanisms. Transcriptomic analysis of the effect of norspermidine on the plant Arabidopsis thaliana indicates upregulation of the response to heat stress and denatured proteins. Accordingly, these polyamines inhibit protein ubiquitylation, both in vivo (in yeast, Arabidopsis, and human Hela cells) and in vitro (with recombinant ubiquitin ligase). This interferes with protein degradation by the proteasome, a situation known to deplete cells of amino acids. Norspermidine treatment of yeast cells induces amino acid depletion, and supplementation of media with amino acids counteracts growth inhibition and cellular amino acid depletion but not inhibition of protein polyubiquitylation. [ABSTRACT FROM AUTHOR]

In contrast to many biotic stresses that plants face, feeding by herbivores produces unique mechanical and chemical signatures. Plants have evolved effective systems to recognise these mechanical stimuli and chemical elicitors at the plasma membrane (PM), where this recognition generates ion fluxes, including an influx of Ca2+ that elicits cellular Ca2+ signalling, production of reactive oxygen species (ROS), and variation in transmembrane potential. These signalling events also function in propagation of long-distance signals (Ca2+ waves, ROS waves, and electrical signals), which contribute to rapid, systemic induction of defence responses. Recent studies have identified several candidate channels or transporters that likely produce these ion fluxes at the PM. Here, we describe the important roles of these channels/transporters in transduction or transmission of herbivory-induced early signalling events, long-distance signals, and jasmonic acid and green leaf volatile signalling in plants. [ABSTRACT FROM AUTHOR]

Although seed vigor is a complex physiological trait controlled by quantitative trait loci, technological advances in the laboratory are being translated into applications for enhancing seed vigor in crop plants. In this article, we summarize and discuss pioneering work in the genetic modification of seed vigor, especially through the over-expression of protein L-isoaspartyl methyltransferase (PIMT, EC 2.1.1.77) in seeds. The impressive success in improving rice seed vigor through the over-expression of PIMT provides a valuable reference for engineering high-vigor seeds for crop production. In recent decades, numerous genes/proteins associated with seed vigor have been identified. It is hoped that such potential candidates may be used in the development of genetically edited crops for a high and stable yield potential in crop production. This possibility is very valuable in the context of a changing climate and increasing world population. [ABSTRACT FROM AUTHOR]

Light is a major regulator of plant growth and development by antagonizing gibberellins ( GA), and we provide evidence for a role of light perception and GA in seed coat formation and seed tolerance to deterioration. We have identified two activation-tagging mutants of Arabidopsis thaliana, cog1-2D and cdf4-1D, with improved seed tolerance to deterioration linked to increased expression of COG1/ DOF1.5 and CDF4/ DOF2.3, respectively. These encode two homologous DOF transcription factors, with COG1 most highly expressed in seeds. Improved tolerance to seed deterioration was reproduced in transgenic plants overexpressing these genes, and loss of function from RNA interference resulted in opposite phenotypes. Overexpressions of COG1 and CDF4 have been described to attenuate various light responses mediated by phytochromes. Accordingly, we found that phyA and phyB mutants exhibit increased seed tolerance to deterioration. The phenotype of tolerance to deterioration conferred by gain of function of COG1 and by loss of function of phytochromes is of maternal origin, is also observed under natural aging conditions and correlates with a seed coat with increased suberin and reduced permeability. In developing siliques of the cog1-2D mutant the expression of the GA biosynthetic gene GA3 OX3 and levels of GA1 are higher than in the wild type. These results explain the antagonism between phytochromes and COG1 in terms of the inhibition and the activation, respectively, of GA action. [ABSTRACT FROM AUTHOR]

Replication protein A (RPA) is a heterotrimeric, single-stranded DNA binding complex required for eukaryotic DNA replication, repair, and recombination. RPA is composed of three subunits, RPA1, RPA2, and RPA3. In contrast to single RPA subunit genes generally found in animals and yeast, plants encode multiple paralogs of RPA subunits, suggesting subfunctionalization. Genetic analysis demonstrates that five Arabidopsis thaliana RPA1 paralogs (RPA1A to RPA1E) have unique and overlapping functions in DNA replication, repair, and meiosis. We hypothesize here that RPA1 subfunctionalities will be reflected in major structural and sequence differences among the paralogs. To address this, we analyzed amino acid and nucleotide sequences of RPA1 paralogs from 25 complete genomes representing a wide spectrum of plants and unicellular green algae. We find here that the plant RPA1 gene family is divided into three general groups termed RPA1A, RPA1B, and RPA1C, which likely arose from two progenitor groups in unicellular green algae. In the family Brassicaceae the RPA1B and RPA1C groups have further expanded to include two unique sub-functional paralogs RPA1D and RPA1E, respectively. In addition, RPA1 groups have unique domains, motifs, cis-elements, gene expression profiles, and pattern of conservation that are consistent with proposed functions in monocot and dicot species, including a novel C-terminal zinc-finger domain found only in plant RPA1C-like sequences. These results allow for improved prediction of RPA1 subunit functions in newly sequenced plant genomes, and potentially provide a unique molecular tool to improve classification of Brassicaceae species. [ABSTRACT FROM AUTHOR]

Seed longevity is the most important trait related to the management of gene banks because it governs the regeneration cycle of seeds. Thus, seed longevity is a quantitative trait. Prior to the discovery of molecular markers, classical genetic studies have been performed to identify the genetic determinants of this trait. Post-2000 saw the use of DNA-based molecular markers and modern biotechnological tools, including RNA sequence (RNA-seq) analysis, to understand the genetic factors determining seed longevity. This review summarizes the most important and relevant genetic studies performed in Arabidopsis (24 reports), rice (25 reports), barley (4 reports), wheat (9 reports), maize (8 reports), soybean (10 reports), tobacco (2 reports), lettuce (1 report) and tomato (3 reports), in chronological order, after discussing some classical studies. The major genes identified and their probable roles, where available, are debated in each case. We conclude by providing information about many different collections of various crops available worldwide for advanced research on seed longevity. Finally, the use of new emerging technologies, including RNA-seq, in seed longevity research is emphasized by providing relevant examples. [ABSTRACT FROM AUTHOR]

Simple Summary: Seeds are the reproductive units of higher plants. They have a significant place in agriculture and plant diversity maintenance. Because they are dehydrated, they can remain viable in the environment for centuries. This review explores the dry seed as a metabolically inactive organism, but well organized to protect its components and enter intensive repair to restore metabolic activities upon imbibition for the completion of germination. Metabolism regulation is also critical for the most important seed traits, dormancy, and ageing recovery capacity. The seed represents a critical stage in the life cycle of flowering plants. It corresponds to a dry structure carrying the plant embryo in dormant or quiescent state. Orthodox seeds possess a very low water content, preventing biochemical reactions, especially respiration. If the desiccation of living organisms leads to a loss of homeostasis, structure, and metabolism, the seeds go through it successfully thanks to their structure, cellular organization, and growth regulation. Seeds set up a certain number of sophisticated molecules to protect valuable macromolecules or organelles from dehydration/rehydration cycles. Moreover, dormancy takes place in a coordinated process with environmental cues in order to ensure embryo development at the most appropriate conditions for the establishment of the new plant. Moreover, repair processes are programmed to be ready to operate to maximize germination success and seed longevity. This review focuses on the physiology of the seed as related to hydration forces, respiration, and biochemical reactions in the transition from thermodynamically undefined dry state to self-sustained living system. Such processes are of importance for basic knowledge of the regulation of metabolism of living organisms, but also for the control of germination in the context of climate change due to global warming. [ABSTRACT FROM AUTHOR]

Seed is the dissemination unit of plants initiating an important stage in the life cycle of plants. Seed development, comprising two phases: embryogenesis and seed maturation, may define the quality of sown seed, especially under abiotic stress. In this review we have focused on the recent advances in the molecular mechanisms underlying these complex processes and how they are controlled by distinct environmental factors regulating ion homeostasis into the seed tissues. The role of transporters affecting seed embryogenesis and first stages of germination as imbibition and subsequent radicle protrusion and extension were revised from a molecular point of view. Seed formation depends on the loading of nutrients from the maternal seed coat to the filial endosperm, a process of which the efflux is not clear and where different ions and transporters are involved. The clear interrelation between soil nutrients, presence of heavy metals and the ion capacity of penetration through the seed are discussed in terms of ion effect during different germination stages. Results concerning seed priming techniques used in the improvement of seed vigor and radicle emergence are shown, where the use of nutrients as a novel way of osmopriming to alleviate abiotic stress effects and improve seedlings yield is discussed. Novel approaches to know the re-translocation from source leaves to developing seeds are considered, as an essential mechanism to understand the biofortification process of certain grains in order to cope with nutrient deficiencies, especially in arid and semiarid areas. Finally, the role of new genes involved in hormone-dependent processes, oxidative response and water uptake into the seeds during their development or germination, have been described as plant mechanisms to deal with abiotic stresses. [ABSTRACT FROM AUTHOR]

Intracellular acid stress inhibits plant growth by unknown mechanisms and it occurs in acidic soils and as consequence of other stresses. In order to identify mechanisms of acid toxicity, we screened activation-tagging lines of Arabidopsis thaliana for tolerance to intracellular acidification induced by organic acids. A dominant mutant, sbt4.13-1D, was isolated twice and shown to over-express subtilase SBT4.13, a protease secreted into endoplasmic reticulum. Activity measurements and immuno-detection indicate that the mutant contains less plasma membrane H+-ATPase (PMA) than wild type, explaining the small size, electrical depolarization and decreased cytosolic pH of the mutant but not organic acid tolerance. Addition of acetic acid to wild-type plantlets induces production of ROS (Reactive Oxygen Species) measured by dichlorodihydrofluorescein diacetate. Acid-induced ROS production is greatly decreased in sbt4.13-1D and atrboh-D,F mutants. The latter is deficient in two major NADPH oxidases (NOXs) and is tolerant to organic acids. These results suggest that intracellular acidification activates NOXs and the resulting oxidative stress is important for inhibition of growth. The inhibition of acid-activated NOXs in the sbt4.13-1D mutant compensates inhibition of PMA to increase acid tolerance. [ABSTRACT FROM AUTHOR]

Bicarbonate plays a fundamental role in the cell pH status in all organisms. In autotrophs, HCO3− may further contribute to carbon concentration mechanisms (CCM). This is especially relevant in the CO2-poor habitats of cyanobacteria, aquatic microalgae, and macrophytes. Photosynthesis of terrestrial plants can also benefit from CCM as evidenced by the evolution of C4 and Crassulacean Acid Metabolism (CAM). The presence of HCO3− in all organisms leads to more questions regarding the mechanisms of uptake and membrane transport in these different biological systems. This review aims to provide an overview of the transport and metabolic processes related to HCO3− in microalgae, macroalgae, seagrasses, and terrestrial plants. HCO3− transport in cyanobacteria and human cells is much better documented and is included for comparison. We further comment on the metabolic roles of HCO3− in plants by focusing on the diversity and functions of carbonic anhydrases and PEP carboxylases as well as on the signaling role of CO2/HCO3− in stomatal guard cells. Plant responses to excess soil HCO3− is briefly addressed. In conclusion, there are still considerable gaps in our knowledge of HCO3− uptake and transport in plants that hamper the development of breeding strategies for both more efficient CCM and better HCO3− tolerance in crop plants. [ABSTRACT FROM AUTHOR]