Physiological and Transcriptomic Analysis of Arabidopsis thaliana Responses to Ailanthone, a Potential Bio-Herbicide.

Many plants naturally synthesize and secrete secondary metabolites that exert an allelopathic effect, offering compelling alternatives to chemical herbicides. These natural herbicides are highly important for sustainable agricultural practices. Ailanthone is the chemical responsible for the herbicidal effect of Ailanthus altissima, or "tree of heaven". The molecular studies involving ailanthone's effect on plant growth are limited. In the current study, we combined whole-transcriptome and physiology analysis of three Arabidopsis thaliana ecotypes treated with ailanthone to identify the effect of this allelopathic chemical on genes and plant growth. Our physiology results showed 50% reduced root growth, high proline accumulation, and high reactive-oxygen-species accumulation in response to ailanthone stress. Deep transcriptome analysis revealed 528, 473, and 482 statistically significant differentially expressed genes for Col-0, Cvi-0, and U112-3 under ailanthone stress, including 131 genes shared among the three accessions. The common genes included 82 upregulated and 42 downregulated genes and varied in expression at least twofold. The study also revealed that 34 of the 131 genes had a similar expression pattern when Arabidopsis seedlings were subjected to other herbicides. Differentially expressed genes significantly induced in response to ailanthone included DTXL1, DTX1, ABCC3, NDB4, UGT74E2, and AZI1. Pathways of stress, development and hormone metabolism were significantly altered under ailanthone stress. These results suggest that ailanthone triggers a significant stress response in multiple pathways similar to other herbicides.

Exploration into natural variation for genes associated with fruit shape and size among Capsicum chinense collections.

Phenotype diversity within cultivated Capsicum chinense is particularly evident for fruit shape and size. We used this diversity in C. chinense to further unravel the genetic mechanisms underlying fruit shape variation in pepper and related Solanaceous species. We identified candidate genes for C. chinense fruit shape, explored their contribution to population structure, and characterized their potential function in pepper fruit shape. Using genotyping by sequencing, we identified 43,081 single nucleotide polymorphisms (SNPs) from diverse collections of C. chinense. Principal component, neighbor-joining tree, and population structure analyses resolved 3 phylogenetically robust clusters associated with fruit shapes. Genome-wide association study (GWAS) was used to identify associated genomic regions with various fruit shape traits obtained from image analysis with Tomato Analyzer software. In our GWAS, we selected 12 SNPs associated with locule number trait and 8 SNP markers associated with other fruit shape traits such as perimeter, area, obovoid, ellipsoid and morphometrics (5y, 6y and 7y). The SNPs in CLAVATA1, WD-40, Auxin receptor, AAA type ATPase family protein, and RNA polymerase III genes were the major markers identified for fruit locule number from our GWAS results. Furthermore, we found SNPs in tetratricopeptide-repeat thioredoxin-like 3, enhancer of ABA co-receptor 1, subunit of exocyst complex 8 and pleiotropic drug resistance proteins associated with various fruit shape traits. CLAVATA1, WD-40 and Auxin receptor genes are known genes that affect tomato fruit shape. In this study, we used Arabidopsis thaliana T-DNA insertion knockout mutants and expression profiles for functional characterization of newly identified genes and to understand their role in fruit shape.

Histochemical Techniques in Plant Science: More Than Meets the Eye.

Histochemistry is an essential analytical tool interfacing extensively with plant science. The literature is indeed constellated with examples showing its use to decipher specific physiological and developmental processes, as well as to study plant cell structures. Plant cell structures are translucent unless they are stained. Histochemistry allows the identification and localization, at the cellular level, of biomolecules and organelles in different types of cells and tissues, based on the use of specific staining reactions and imaging. Histochemical techniques are also widely used for the in vivo localization of promoters in specific tissues, as well as to identify specific cell wall components such as lignin and polysaccharides. Histochemistry also enables the study of plant reactions to environmental constraints, e.g. the production of reactive oxygen species (ROS) can be traced by applying histochemical staining techniques. The possibility of detecting ROS and localizing them at the cellular level is vital in establishing the mechanisms involved in the sensitivity and tolerance to different stress conditions in plants. This review comprehensively highlights the additional value of histochemistry as a complementary technique to high-throughput approaches for the study of the plant response to environmental constraints. Moreover, here we have provided an extensive survey of the available plant histochemical staining methods used for the localization of metals, minerals, secondary metabolites, cell wall components, and the detection of ROS production in plant cells. The use of recent technological advances like CRISPR/Cas9-based genome-editing for histological application is also addressed. This review also surveys the available literature data on histochemical techniques used to study the response of plants to abiotic stresses and to identify the effects at the tissue and cell levels.

Genome-Wide Association Study of Natural Variation in Arabidopsis Exposed to Acid Mine Drainage Toxicity and Validation of Associated Genes with Reverse Genetics.

Acid mine drainage (AMD) is a huge environmental problem in mountain-top mining regions worldwide, including the Appalachian Mountains in the United States. This study applied a genome-wide association study (GWAS) to uncover genomic loci in Arabidopsis associated with tolerance to AMD toxicity. We characterized five major root phenotypes-cumulative root length, average root diameter, root surface area, root volume, and primary root length-in 180 Arabidopsis accessions in response to AMD-supplemented growth medium. GWAS of natural variation in the panel revealed genes associated with tolerance to an acidic environment. Most of these genes were transcription factors, anion/cation transporters, metal transporters, and unknown proteins. Two T-DNA insertion mutants, At1g63005 (miR399b) and At2g05635 (DEAD helicase RAD3), showed enhanced acidity tolerance. Our GWAS and the reverse genetic approach revealed genes involved in conferring tolerance to coal AMD. Our results indicated that proton resistance in hydroponic conditions could be an important index to improve plant growth in acidic soil, at least in acid-sensitive plant species.

Arsenic Stress-Related F-Box (ASRF) gene regulates arsenic stress tolerance in Arabidopsis thaliana.

Arsenic (As), a non-biodegradable contaminant, is extremely toxic to plants and animals in its inorganic form. As negatively affects plant growth and development, primarily by inducing oxidative stress through redox imbalance. Here we characterized the Arabidopsis F-box protein gene AT2G16220 (Arsenic Stress-Related F-box (ASRF)) that we identified in the genome-wide association study. The asrf mutant seedlings showed high sensitivity to arsenate (AsV) stress. AsV significantly affected asrf seedling growth when germinated on or exposed to AsV-supplemented growth regimes. AsV stress significantly induced production of reactive oxygen species and proline accumulation in asrf, so the asrf maintained high proline content, possibly for cellular protection and redox homeostasis. Heterozygous seedlings (Col-0 x asrf, F1 progeny) were relatively less affected by AsV stress than asrf mutant but showed slightly reduced growth compared with the Col-0 wild type, which suggests that the homozygous ASRF locus is important for AsV stress resistance. Transcriptome analysis involving the mutant and wild type revealed altered phosphate homeostasis in asrf seedlings, which implies that ASRF is required for maintaining phosphate and cellular- homeostasis under excess AsV. Our findings confirm the roles of ASRF in As stress tolerance in plants, for a novel way to mitigate arsenic stress.

Harnessing High-throughput Phenotyping and Genotyping for Enhanced Drought Tolerance in Crop Plants.

Development of drought-tolerant cultivars is one of the challenging tasks for the plant breeders due to its complex inheritance and polygenic regulation. Evaluating genetic material for drought tolerance is a complex process due to its spatiotemporal interactions with environmental factors. The conventional breeding approaches are costly, lengthy, and inefficient to achieve the expected gain in drought tolerance. In this regard, genomics-assisted breeding (GAB) offers promise to develop cultivars with improved drought tolerance in a more efficient, quicker, and cost-effective manner. The success of GAB depends upon the precision in marker-trait association and estimation of genomic estimated breeding values (GEBVs), which mostly depends on coverage and precision of genotyping and phenotyping. A wide gap between the discovery and practical use of quantitative trait loci (QTL) for crop improvement has been observed for many important agronomical traits. Such a limitation could be due to the low accuracy in QTL detection, mainly resulting from low marker density and manually collected phenotypes of complex agronomic traits. Increasing marker density using the high-throughput genotyping (HTG), and accurate and precise phenotyping using high-throughput digital phenotyping (HTP) platforms can improve the precision and power of QTL detection. Therefore, both HTG and HTP can enhance the practical utility of GAB along with a faster characterization of germplasm and breeding material. In the present review, we discussed how the recent innovations in HTG and HTP would assist in the breeding of improved drought-tolerant varieties. We have also discussed strategies, tools, and analytical advances made on the HTG and HTP along with their pros and cons.

Understanding aquaporin transport system in highly stress-tolerant and medicinal plant species Jujube (Ziziphus jujuba Mill.).

Jujube (Ziziphus jujubaMill.), a deciduous tree, is well known for its medicinal and nutritional values. Being an extremophile, it has an excellent capability to survive under arid conditions with limited water availability. In this regard, studying the role of water transport regulating proteins such as Aquaporins (AQPs) in jujube is of great importance. Aquaporins, channel-forming proteins are known to have a significant role in the transport of water and many other small solutes in plants. In the present study, computational approaches have identified 36 AQPs, which comprised of 12 NIPs (Nodulin 26-like intrinsic proteins), 10 PIPs (Plasma membrane intrinsic proteins), 10 TIPs (Tonoplast intrinsic proteins), 3 SIPs (Small intrinsic proteins), and 1 XIP (uncharacterized intrinsic protein). Conserved features of AQPs like asparagines-proline-alanine (NPA) amino acid motifs, aromatic/arginine (ar/R) selectivity filters, and Frogger's residues, having a significant role in solute specificity and transport, were also predicted. Homology-based tertiary (3D) structures of AQPS were also resolved using various tools, and subsequently, pore-lining residues have been identified using the 3D structures. The information of pore morphology, along with the conserved features provided through this work, will be helpful to predict solute specificity of AQPs. Analysis of transcriptomic data revealed the tissue-specific or ubiquitous expression of several AQPs in different tissues of jujube. Interestingly, TIP3-1 was found to have fruit specific expression whereas most of the AQPs have a relatively low expression. Based on the present study and previous reports, TIP3s seems to have a significant role in seed desiccation processes. The findings presented here provide pivotal insights into the functions of extremophile specific AQPs, to better understand the role of AQPs and, subsequently, the stress tolerance mechanism in jujube.

Significance of silicon uptake, transport, and deposition in plants.

Numerous studies have shown the beneficial effects of silicon (Si) for plant growth, particularly under stress conditions, and hence a detailed understanding of the mechanisms of its uptake, subsequent transport, and accumulation in different tissues is important. Here, we provide a thorough review of our current knowledge of how plants benefit from Si supplementation. The molecular mechanisms involved in Si transport are discussed and we highlight gaps in our knowledge, particularly with regards to xylem unloading and transport into heavily silicified cells. Silicification of tissues such as sclerenchyma, fibers, storage tissues, the epidermis, and vascular tissues are described. Silicon deposition in different cell types, tissues, and intercellular spaces that affect morphological and physiological properties associated with enhanced plant resilience under various biotic and abiotic stresses are addressed in detail. Most Si-derived benefits are the result of interference in physiological processes, modulation of stress responses, and biochemical interactions. A better understanding of the versatile roles of Si in plants requires more detailed knowledge of the specific mechanisms involved in its deposition in different tissues, at different developmental stages, and under different environmental conditions.

Haplotype Networking of GWAS Hits for Citrulline Variation Associated with the Domestication of Watermelon.

Watermelon is a good source of citrulline, a non-protein amino acid. Citrulline has several therapeutic and clinical implications as it produces nitric oxide via arginine. In plants, citrulline plays a pivotal role in nitrogen transport and osmoprotection. The purpose of this study was to identify single nucleotide polymorphism (SNP) markers associated with citrulline metabolism using a genome-wide association study (GWAS) and understand the role of citrulline in watermelon domestication. A watermelon collection consisting of 187 wild, landraces, and cultivated accessions was used to estimate citrulline content. An association analysis involved a total of 12,125 SNPs with a minor allele frequency (MAF) >0.05 in understanding the population structure and phylogeny in light of citrulline accumulation. Wild egusi types and landraces contained low to medium citrulline content, whereas cultivars had higher content, which suggests that obtaining higher content of citrulline is a domesticated trait. GWAS analysis identified candidate genes (ferrochelatase and acetolactate synthase) showing a significant association of SNPs with citrulline content. Haplotype networking indicated positive selection from wild to domesticated watermelon. To our knowledge, this is the first study showing genetic regulation of citrulline variation in plants by using a GWAS strategy. These results provide new insights into the citrulline metabolism in plants and the possibility of incorporating high citrulline as a trait in watermelon breeding programs.

Elevated carbon dioxide and drought modulate physiology and storage-root development in sweet potato by regulating microRNAs.

Elevated CO2 along with drought is a serious global threat to crop productivity. Therefore, understanding the molecular mechanisms plants use to protect these stresses is the key for plant growth and development. In this study, we mimicked natural stress conditions under a controlled Soil-Plant-Atmosphere-Research (SPAR) system and provided the evidence for how miRNAs regulate target genes under elevated CO2 and drought conditions. Significant physiological and biomass data supported the effective utilization of source-sink (leaf to root) under elevated CO2. Additionally, elevated CO2 partially rescued the effect of drought on total biomass. We identified both known and novel miRNAs differentially expressed during drought, CO2, and combined stress, along with putative targets. A total of 32 conserved miRNAs belonged to 23 miRNA families, and 25 novel miRNAs were identified by deep sequencing. Using the existing sweet potato genome database and stringent analyses, a total of 42 and 22 potential target genes were predicted for the conserved and novel miRNAs, respectively. These target genes are involved in drought response, hormone signaling, photosynthesis, carbon fixation, sucrose and starch metabolism, etc. Gene ontology and KEGG ontology functional enrichment revealed that these miRNAs might target transcription factors (MYB, TCP, NAC), hormone signaling regulators (ARF, AP2/ERF), cold and drought factors (corA), carbon metabolism (ATP synthase, fructose-1,6-bisphosphate), and photosynthesis (photosystem I and II complex units). Our study is the first report identifying targets of miRNAs under elevated CO2 levels and could support the molecular mechanisms under elevated CO2 in sweet potato and other crops in the future.

Friedel-Crafts Alkylation over Zr-Mont Catalyst for the Production of Diesel Fuel Precursors.

Heterogeneous Zr-Mont catalyst prepared by a simple protocol was employed for the production of diesel fuel precursors via Friedel-Crafts (FC) alkylation of petroleum-derived arenes (e.g., mesitylene, xylene, and toluene) with biomass-derived 5-(hydroxymethyl)furfural (HMF), HMF derivatives, and carbohydrates. Initially, several acidic catalysts were screened for the FC alkylation of mesitylene with HMF in nitroethane solvent. Among all, Zr-Mont catalyst gave an exceptionally high yield (80%) of mesitylmethylfurfural (MMF). The catalytic activity of Zr-Mont was also evaluated for the alkylation of different petroleum-derived arenes with ester/halogen derivatives of HMF. Suitable acid strength and high surface area of Zr-Mont were its major attributes to make it the most efficient solid acid catalyst for this FC reaction. Even after several reuses, the catalytic activity of Zr-Mont was found to be consistent, which was also evidenced by the acidity measurements of fresh and reused Zr-Mont catalysts by temperature-programmed desorption of ammonia and pyridine Fourier transform infrared spectroscopy techniques. Direct conversion of glucose to diesel fuel precursors was also attempted over Zr-Mont catalyst in mesitylene and polar nonacidic solvents at 150 °C. However, the activity of Zr-Mont catalyst was limited for glucose dehydration to HMF and MMF did not form. When the same experiment was performed in formic acid medium, MMF was produced in 34% yield. After the addition of formic acid, the reaction becomes biphasic which contains mesitylene as an organic phase and formic acid as an aqueous phase. Formic acid worked as a solvent, reactant, and cocatalyst, whereas mesitylene worked as a reactant and product extraction phase to enable easy product isolation. With this strategy, other diesel fuel precursors were also produced in 26-30% yields from glucose and different arenes. Similar strategy was successfully extended for the conversion of sucrose to diesel fuel precursors.

Cascade Reductive Etherification of Bioderived Aldehydes over Zr-Based Catalysts.

An efficient one-pot catalytic cascade sequence has been developed for the production of value-added ethers from bioderived aldehydes. Etherification of 5-(hydroxymethyl)furfural with different aliphatic alcohols over acidic Zr-montmorillonite (Zr-Mont) catalyst produced a mixture of 5-(alkoxymethyl)furfural and 2-(dialkoxymethyl)-5-(alkoxymethyl)furan. The latter was selectively converted back into 5-(alkoxymethyl)furfural by treating it with water over the same catalyst. The synthesis of 2,5-bis(alkoxymethyl)furan was achieved through a cascade sequence involving etherification, transfer hydrogenation, and re-etherification over a combination of acidic Zr-Mont and the charge-transfer hydrogenation catalyst [ZrO(OH)2 ]. This catalyst combination was further explored for the cascade conversion of 2-furfuraldehyde into 2-(alkoxymethyl)furan. The scope of this strategy was then extended for the reductive etherification of lignin-derived arylaldehydes to obtain the respective benzyl ethers in >80 % yield. Additionally, the mixture of Zr-Mont and ZrO(OH)2 does not undergo mutual destruction, which was proved by recycling experiments and XRD analysis. Both the catalysts were thoroughly characterized using BET, temperature-programmed desorption of NH3 and CO2 , pyridine-FTIR, XRD, inductively coupled plasma optical emission spectroscopy, and X-ray photoelectron spectroscopy techniques.

Profiling Abscisic Acid-Induced Changes in Fatty Acid Composition in Mosses.

In plants, change in lipid composition is a common response to various abiotic stresses. Lipid constituents of bryophytes are of particular interest as they differ from that of flowering plants. Unlike higher plants, mosses have high content of very long-chain polyunsaturated fatty acids. Such lipids are considered to be important for survival of nonvascular plants. Here, using abscisic acid (ABA )-induced changes in lipid composition in Physcomitrella patens as an example, a protocol for total lipid extraction and quantification by gas chromatography (GC) coupled with flame ionization detector (FID) is described.

Proline Coordination with Fatty Acid Synthesis and Redox Metabolism of Chloroplast and Mitochondria.

Proline (Pro) accumulation is one of the most prominent changes in plant metabolism during drought and low water potential; however, the regulation and function of Pro metabolism remain unclear. We used a combination of forward genetic screening based on a Proline Dehydrogenase1 (PDH1) promoter-luciferase reporter (PDH1pro:LUC2) and RNA sequencing of the Pro synthesis mutant p5cs1-4 to identify multiple loci affecting Pro accumulation in Arabidopsis (Arabidopsis thaliana). Two mutants having high PDH1pro:LUC2 expression and increased Pro accumulation at low water potential were found to be alleles of Cytochrome P450, Family 86, Subfamily A, Polypeptide2 (CYP86A2) and Long Chain Acyl Synthetase2 (LACS2), which catalyze two successive steps in very-long-chain fatty acid (VLCFA) synthesis. Reverse genetic experiments found additional VLCFA and lipid metabolism-related mutants with increased Pro accumulation. Altered cellular redox status is a key factor in the coordination of Pro and VLCFA metabolism. The NADPH oxidase inhibitor diphenyleneiodonium (DPI) induced high levels of Pro accumulation and strongly repressed PDH1pro:LUC2 expression. cyp86a2 and lacs2 mutants were hypersensitive to diphenyleneiodonium but could be reverted to wild-type Pro and PDH1pro:LUC2 expression by reactive oxygen species scavengers. The coordination of Pro and redox metabolism also was indicated by the altered expression of chloroplast and mitochondria electron transport genes in p5cs1-4 These results show that Pro metabolism is both influenced by and influences cellular redox status via previously unknown coordination with several metabolic pathways. In particular, Pro and VLCFA synthesis share dual roles to help buffer cellular redox status while producing products useful for stress resistance, namely the compatible solute Pro and cuticle lipids.

Genome-wide transcriptomic analysis of the effects of sub-ambient atmospheric oxygen and elevated atmospheric carbon dioxide levels on gametophytes of the moss, Physcomitrella patens.

It is widely accepted that atmospheric O2 has played a key role in the development of life on Earth, as evident from the coincidence between the rise of atmospheric O2 concentrations in the Precambrian and biological evolution. Additionally, it has also been suggested that low atmospheric O2 is one of the major drivers for at least two of the five mass-extinction events in the Phanerozoic. At the molecular level, our understanding of the responses of plants to sub-ambient O2 concentrations is largely confined to studies of the responses of underground organs, e.g. roots to hypoxic conditions. Oxygen deprivation often results in elevated CO2 levels, particularly under waterlogged conditions, due to slower gas diffusion in water compared to air. In this study, changes in the transcriptome of gametophytes of the moss Physcomitrella patens arising from exposure to sub-ambient O2 of 13% (oxygen deprivation) and elevated CO2 (1500 ppmV) were examined to further our understanding of the responses of lower plants to changes in atmospheric gaseous composition. Microarray analyses revealed that the expression of a large number of genes was affected under elevated CO2 (814 genes) and sub-ambient O2 conditions (576 genes). Intriguingly, the expression of comparatively fewer numbers of genes (411 genes) was affected under a combination of both sub-ambient O2 and elevated CO2 condition (low O2-high CO2). Overall, the results point towards the effects of atmospheric changes in CO2 and O2 on transcriptional reprogramming, photosynthetic regulation, carbon metabolism, and stress responses.

Functional characterization of an ornithine cyclodeaminase-like protein of Arabidopsis thaliana.

BACKGROUND: In plants, proline synthesis occurs by two enzymatic steps starting from glutamate as a precursor. Some bacteria, including bacteria such as Agrobacterium rhizogenes have an Ornithine Cyclodeaminase (OCD) which can synthesize proline in a single step by deamination of ornithine. In A. rhizogenes, OCD is one of the genes transferred to the plant genome during the transformation process and plants expressing A. rhizogenes OCD have developmental phenotypes. One nuclear encoded gene of Arabidopsis thaliana has recently been annotated as an OCD (OCD-like; referred to here as AtOCD) but nothing is known of its function. As proline metabolism contributes to tolerance of low water potential during drought, it is of interest to determine if AtOCD affects proline accumulation or low water potential tolerance. RESULTS: Expression of AtOCD was induced by low water potential stress and by exogenous proline, but not by the putative substrate ornithine. The AtOCD protein was plastid localized. T-DNA mutants of atocd and AtOCD RNAi plants had approximately 15% higher proline accumulation at low water potential while p5cs1-4/atocd double mutants had 40% higher proline than p5cs1 at low water potential but no change in proline metabolism gene expression which could directly explain the higher proline level. AtOCD overexpression did not affect proline accumulation. Enzymatic assays with bacterially expressed AtOCD or AtOCD purified from AtOCD:Flag transgenic plants did not detect any activity using ornithine, proline or several other amino acids as substrates. Moreover, AtOCD mutant or over-expression lines had normal morphology and no difference in root elongation or flowering time, in contrast to previous report of transgenic plants expressing A. rhizogenes OCD. Metabolite analysis found few differences between AtOCD mutants and overexpression lines. CONCLUSIONS: The Arabidopsis OCD-like protein (AtOCD) may not catalyze ornithine to proline conversion and this is consistent with observation that three residues critical for activity of bacterial OCDs are not conserved in AtOCD. AtOCD was, however, stress and proline induced and lack of AtOCD expression increased proline accumulation by an unknown mechanism which did not require expression of P5CS1, the main enzyme responsible for stress-induced proline synthesis from glutamate. The results suggest that AtOCD may have function distinct from bacterial OCDs.

Abiotic stress-induced oscillations in steady-state transcript levels of Group 3 LEA protein genes in the moss, Physcomitrella patens.

The moss, Physcomitrella patens is a non-seed land plant belonging to early diverging lineages of land plants following colonization of land in the Ordovician period in Earth's history. Evidence suggests that mosses can be highly tolerant of abiotic stress. We showed previously that dehydration stress and abscisic acid treatments induced oscillations in steady-state levels of LEA (Late Embryogenesis Abundant) protein transcripts, and that removal of ABA resulted in rapid attenuation of oscillatory increases in transcript levels. Here, we show that other abiotic stresses like salt and osmotic stresses also induced oscillations in steady-state transcript levels and that the amplitudes of the oscillatory increases in steady-state transcript levels are reflective of the severity of the abiotic stress treatment. Together, our results suggest that oscillatory increases in transcript levels in response to abiotic stresses may be a general phenomenon in P. patens and that temporally dynamic increases in steady-state transcript levels may be important for adaptation to life in constantly fluctuating environmental conditions.

Dehydration stress-induced oscillations in LEA protein transcripts involves abscisic acid in the moss, Physcomitrella patens.

• Physcomitrella patens is a bryophyte belonging to early diverging lineages of land plants following colonization of land in the Ordovician period. Mosses are typically found in refugial habitats and can experience rapidly fluctuating environmental conditions. The acquisition of dehydration tolerance by bryophytes is of fundamental importance as they lack water-conducting tissues and are generally one cell layer thick. • Here, we show that dehydration induced oscillations in the steady-state transcript abundances of two group 3 late embryogenesis abundant (LEA) protein genes in P. patens protonemata, and that the amplitudes of these oscillations are reflective of the severity of dehydration stress. • Dehydration stress also induced elevations in the concentrations of abscisic acid (ABA), and ABA alone can also induce dosage-dependent oscillatory increases in the steady-state abundance of LEA protein transcripts. Additionally, removal of ABA resulted in rapid attenuation of these oscillatory increases. • Our data demonstrate that dehydration stress-regulated expression of LEA protein genes is temporally dynamic and highlight the importance of oscillations as a robust mechanism for optimal responses. Our results suggest that dehydration stress-induced oscillations in the steady-state abundance of LEA protein transcripts may constitute an important cellular strategy for adaptation to life in a constantly changing environment.