Down-regulation of CBP80 gene expression as a strategy to engineer a drought-tolerant potato

The cap-binding complex modulates ABA-responsive transcript splicing during germination in barley (Hordeum vulgare)

To decipher the molecular bases governing seed germination, this study presents the pivotal role of the cap-binding complex (CBC), comprising CBP20 and CBP80, in modulating the inhibitory effects of abscisic acid (ABA) in barley. Using both single and double barley mutants in genes encoding the CBC, we revealed that the double mutant hvcbp20.ab/hvcbp80.b displays ABA insensitivity, in stark contrast to the hypersensitivity observed in single mutants during germination. Our comprehensive transcriptome and metabolome analysis not only identified significant alterations in gene expression and splicing patterns but also underscored the regulatory nexus among CBC, ABA, and brassinosteroid (BR) signaling pathways.

miRNAs: Primary modulators of plant drought tolerance

Drought is a principal environmental factor that affects the growth and development of plants. Accordingly, plants have evolved adaptive mechanisms to cope with adverse environmental conditions. One of the mechanisms is gene regulation mediated by microRNAs (miRNAs). miRNAs are regarded as primary modulators of gene expression at the post-transcriptional level and have been shown to participate in drought stress response, including ABA response, auxin signaling, antioxidant defense, and osmotic regulation through downregulating the corresponding targets. miRNA-based genetic reconstructions have the potential to improve the tolerance of plants to drought. However, there are few precise classification and discussion of miRNAs in specific response behaviors to drought stress and their applications. This review summarized and discussed the specific response behaviors of miRNAs under drought stress and the role of miRNAs as regulators in the response of plants to drought and highlighted that the modification of miRNAs might effectively improve the tolerance of plants to drought.

Creating Climate-Resilient Crops by Increasing Drought, Heat, and Salt Tolerance

Over the years, the changes in the agriculture industry have been inevitable, considering the need to feed the growing population. As the world population continues to grow, food security has become challenged. Resources such as arable land and freshwater have become scarce due to quick urbanization in developing countries and anthropologic activities; expanding agricultural production areas is not an option. Environmental and climatic factors such as drought, heat, and salt stresses pose serious threats to food production worldwide. Therefore, the need to utilize the remaining arable land and water effectively and efficiently and to maximize the yield to support the increasing food demand has become crucial. It is essential to develop climate-resilient crops that will outperform traditional crops under any abiotic stress conditions such as heat, drought, and salt, as well as these stresses in any combinations. This review provides a glimpse of how plant breeding in agriculture has evolved to overcome the harsh environmental conditions and what the future would be like.

Gene expression analysis of potato drought-responsive genes under drought stress in potato (Solanum tuberosum L.) cultivars

The potato (Solanum tuberosum L.), an important field crop consumed extensively worldwide, is adversely affected by abiotic stress factors especially drought. Therefore, it is vital to understand the genetic mechanism under drought stress to decrease loose of yield and quality . This trial aimed to screen drought-responsive gene expressions of potato and determine the drought-tolerant potato cultivar. The trial pattern is a completely randomized block design (CRBD) with four replications under greenhouse conditions. Four cultivars (Brooke, Orwell, Vr808, Shc909) were irrigated with four different water regimes (control and three stress conditions), and the gene expression levels of 10 potato genes were investigated. The stress treatments as follows: Control = 100% field capacity; slight drought = 75% field capacity; moderate drought = 50% field capacity, and severe drought 25% field capacity. To understand the gene expression under drought stress in potato genotypes, RT-qPCR analysis was performed and results showed that the genes most associated with drought tolerance were the StRD22 gene, MYB domain transcription factor, StERD7, Sucrose Synthase (SuSy), ABC Transporter, and StDHN1. The StHSP100 gene had the lowest genetic expression in all cultivars. Among the cultivars, the Orwell exhibited the highest expression of the StRD22 gene under drought stress. Overall, the cultivar with the highest gene expression was the Vr808, closely followed by the Brooke cultivar. As a result, it was determined that potato cultivars Orwell, Vr808, and Brooke could be used as parents in breeding programs to develop drought tolerant potato cultivars.

Rhizospheric nano-remediation salvages arsenic genotoxicity: Zinc-oxide nanoparticles articulate better oxidative stress management, reduce arsenic uptake, and increase yield in Pisum sativum (L.)

Pea (Pisum sativum L.), a legume, has a high nutritional content, but arsenic (As) in the agro-ecosystem poses a significant bottleneck to its yield, especially in South East Asia, by severely hampering ontogeny. The present study proposes a rhizospheric nano-remediation strategy to evade As-genotoxicity and improve crop yield using biogenic zinc-oxide nanoparticles (ZnONPs). Similar to any other source of environmental stress, As-toxicity caused rapid oxidative bursts with deterioration in morpho-physiological attributes (germination rate, shoot length, and root length decreased by 62 %, 16 %, and 14.9 % respectively in the negative control, over normal control). Reactive oxygen species (ROS) accumulation (12.8 and 9-fold increase in leaves and roots) overburdened antioxidative defense, and loss of cellular homeostasis resulted in membrane damage (82.75 % increase) and electrolyte-leakage (2.6-fold increase) in negative control. The study also reveals a significant increase in nuclear area, nuclear fragmentation, and micronuclei formation in root tip cells under As-stress, indicating severe genomic instability and increased programmed cell death (3.3-fold increase in early apoptotic cells) due to leaky plasma membrane and unrepaired DNA damage. Application of ZnONPs significantly reduced As-toxicity in peas due to its adsorption in the rhizosphere, causing diminished As-uptake and better antioxidant response. Improved phytochelatin synthesis enhanced vacuolar sequestration of arsenic, which reduced As-interference. Comparatively better flowering time (7.74-19.36 % reduction in flowering delay) with greater transcript abundance of GIGANTIA (GI), CONSTANS (CO), and FLOWERING LOCUS T (FT) genes; better photosynthetic activity (1.3-1.9-fold increased chlorophyll autofluorescence); increased pollen viability; lesser genotoxicity (decreased tail DNA in comet assay) was noticed. A maximum increase of 37.5 % in pod number and seed zinc content (1.67-fold) was observed while seed arsenic content decreased under ZnONPs treatment. However, the highest dose of ZnONPs (400 mg L-1) induced NP-toxicity in pea plants under our experimental conditions, while optimum stress-alleviation was observed up to 300 mg L-1.

Function identification of miR159a, a positive regulator during poplar resistance to drought stress

Drought seriously affects the growth and development of plants. MiR159 is a highly conserved and abundant microRNA family that plays a crucial role in plant growth and stress responses. However, studies of its function in woody plants are still lacking. Here, the expression of miR159a was significantly upregulated after drought treatment in poplar, and the overexpression of miR159a (OX159a) significantly reduced the open area of the stomata and improved water-use efficiency in poplar. After drought treatment, OX159a lines had better scavenging ability of reactive oxygen species and damage of the membrane system was less than that in wild-type lines. MYB was the target gene of miR159a, as verified by psRNATarget prediction, RT-qPCR, degradome sequencing, and 5' rapid amplification of cDNA ends (5' RACE). Additionally, miR159a-short tandem target mimic suppression (STTM) poplar lines showed increased sensitivity to drought stress. Transcriptomic analysis comparing OX159a lines with wild-type lines revealed upregulation of a series of genes related to response to water deprivation and metabolite synthesis. Moreover, drought-responsive miR172d and miR398 were significantly upregulated and downregulated respectively in OX159a lines. This investigation demonstrated that miR159a played a key role in the tolerance of poplar to drought by reducing stomata open area, increasing the number and total area of xylem vessels, and enhancing water-use efficiency, and provided new insights into the role of plant miR159a and crucial candidate genes for the molecular breeding of trees with tolerance to drought stress.

NCBP1 enhanced proliferation of DLBCL cells via METTL3-mediated m6A modification of c-Myc

Diffuse large B-cell lymphoma (DLBCL) is malignant hyperplasia of B lymphocytes and standard care cannot satisfactorily meet clinical needs. Potential diagnostic and prognostic DLBCL biomarkers are needed. NCBP1 could bind to the 5'-end cap of pre-mRNAs to participate in RNA processing, transcript nuclear export and translation. Aberrant NCBP1 expression is involved in the pathogenesis of cancers, but little is known about NCBP1 in DLBCL. We proved that NCBP1 is significantly elevated in DLBCL patients and is associated with their poor prognosis. Then, we found that NCBP1 is important for the proliferation of DLBCL cells. Moreover, we verified that NCBP1 enhances the proliferation of DLBCL cells in a METTL3-dependent manner and found that NCBP1 enhances the m⁶A catalytic function of METTL3 by maintaining METTL3 mRNA stabilization. Mechanistically, the expression of c-MYC is regulated by NCBP1-enhanced METTL3, and the NCBP1/METTL3/m⁶A/c-MYC axis is important for DLBCL progression. We identified a new pathway for DLBCL progression and suggest innovative ideas for molecular targeted therapy of DLBCL.

Application of Indole-Alkaloid Harmaline Induces Physical Damage to Photosystem II Antenna Complexes in Adult Plants of Arabidopsis thaliana (L.) Heynh

Finding herbicides with new and multiple modes of action is a solution to stop the increase in resistant weed species. Harmaline, a natural alkaloid with proven phytotoxic potential, was tested on Arabidopsis adult plants by watering and spraying; watering resulted as the more effective treatment. Harmaline altered several photosynthetic parameters, reducing the efficiency of the light- (Φ_II) and dark-adapted (F_v/F_m) PSII, suggesting physical damages in photosystem II, although dissipation of the energy in excess under the form of heat was not compromised as demonstrated by the significant increase in Φ_NPQ. Metabolomic alterations, such as osmoprotectant accumulation and reduction in sugars' content, also indicate a reduction of photosynthetic efficiency and suggest early senescence and water status alteration induced by harmaline. Data suggest that harmaline might be considered a new phytotoxic molecule interesting for further studies.

Comparative Analysis of the Response to Polyethylene Glycol-Simulated Drought Stress in Roots from Seedlings of "Modern" and "Ancient" Wheat Varieties

Durum wheat is widely cultivated in the Mediterranean, where it is the basis for the production of high added-value food derivatives such as pasta. In the next few years, the detrimental effects of global climate change will represent a serious challenge to crop yields. For durum wheat, the threat of climate change is worsened by the fact that cultivation relies on a few genetically uniform, elite varieties, better suited to intensive cultivation than "traditional" ones but less resistant to environmental stress. Hence, the renewed interest in "ancient" traditional varieties are expected to be more tolerant to environmental stress as a source of genetic resources to be exploited for the selection of useful agronomic traits such as drought tolerance. The aim of this study was to perform a comparative analysis of the effect and response of roots from the seedlings of two durum wheat cultivars: Svevo, a widely cultivated elite variety, and Saragolla, a traditional variety appreciated for its organoleptic characteristics, to Polyethylene glycol-simulated drought stress. The effect of water stress on root growth was analyzed and related to biochemical data such as hydrogen peroxide production, electrolyte leakage, membrane lipid peroxidation, proline synthesis, as well as to molecular data such as qRT-PCR analysis of drought responsive genes and proteomic analysis of changes in the protein repertoire of roots from the two cultivars.

Stimulation of Tomato Drought Tolerance by PHYTOCHROME A and B1B2 Mutations

Drought stress is a severe environmental issue that threatens agriculture at a large scale. PHYTOCHROMES (PHYs) are important photoreceptors in plants that control plant growth and development and are involved in plant stress response. The aim of this study was to identify the role of PHYs in the tomato cv. 'Moneymaker' under drought conditions. The tomato genome contains five PHYs, among which mutant lines in tomato PHYA and PHYB (B1 and B2) were used. Compared to the WT, phyA and phyB1B2 mutants exhibited drought tolerance and showed inhibition of electrolyte leakage and malondialdehyde accumulation, indicating decreased membrane damage in the leaves. Both phy mutants also inhibited oxidative damage by enhancing the expression of reactive oxygen species (ROS) scavenger genes, inhibiting hydrogen peroxide (H₂O₂) accumulation, and enhancing the percentage of antioxidant activities via DPPH test. Moreover, expression levels of several aquaporins were significantly higher in phyA and phyB1B2, and the relative water content (RWC) in leaves was higher than the RWC in the WT under drought stress, suggesting the enhancement of hydration status in the phy mutants. Therefore, inhibition of oxidative damage in phyA and phyB1B2 mutants may mitigate the harmful effects of drought by preventing membrane damage and conserving the plant hydrostatus.

Ascorbate-Glutathione Cycle Genes Families in Euphorbiaceae: Characterization and Evolutionary Analysis

Ascorbate peroxidase (APX), Monodehydroascorbate Reductase (MDAR), Dehydroascorbate Reductase (DHAR) and Glutathione Reductase (GR) enzymes participate in the ascorbate-glutathione cycle, which exerts a central role in the antioxidant metabolism in plants. Despite the importance of this antioxidant system in different signal transduction networks related to development and response to environmental stresses, the pathway has not yet been comprehensively characterized in many crop plants. Among different eudicotyledons, the Euphorbiaceae family is particularly diverse with some species highly tolerant to drought. Here the APX, MDAR, DHAR, and GR genes in Ricinus communis, Jatropha curcas, Manihot esculenta, and Hevea brasiliensis were identified and characterized. The comprehensive phylogenetic and genomic analyses allowed the classification of the genes into different classes, equivalent to cytosolic, peroxisomal, chloroplastic, and mitochondrial enzymes, and revealed the duplication events that contribute to the expansion of these families within plant genomes. Due to the high drought stress tolerance of Ricinus communis, the expression patterns of ascorbate-glutathione cycle genes in response to drought were also analyzed in leaves and roots, indicating a differential expression during the stress. Altogether, these data contributed to the characterization of the expression pattern and evolutionary analysis of these genes, filling the gap in the proposed functions of core components of the antioxidant mechanism during stress response in an economically relevant group of plants.

CRISPR/Cas mediated genome editing in potato: Past achievements and future directions

Genome engineering has been re-shaping plant biotechnology and agriculture. Crop improvement using the recently developed gene editing techniques is now easier, faster, and more precise than ever. Although considered to be a global food security crop, potato has not benefitted enough from diverse collection of these techniques. Unique genetic features of cultivated potatoes such as tetrasomic inheritance, high genomic heterozygosity, and inbreeding depression hamper conventional breeding of this important crop. Therefore, genome editing provides an excellent arsenal of tools for trait improvement in potato. Moreover, using specific transformation protocols, it is possible to engineer transgene free commercial varieties. In this review we first describe the past achievements in potato genome editing and highlight some of the missing aspects of these efforts. Then, we discuss about technical challenges of genome editing in potato and present approaches to overcome these difficulties. Finally, we talk about genome editing applications that have not been explored in potato and point out some of the missing venues in literature.

MicroRNAs Mediated Plant Responses to Salt Stress

One of the most damaging issues to cultivatable land is soil salinity. While salt stress influences plant growth and yields at low to moderate levels, severe salt stress is harmful to plant growth. Mineral shortages and toxicities frequently exacerbate the problem of salinity. The growth of many plants is quantitatively reduced by various levels of salt stress depending on the stage of development and duration of stress. Plants have developed various mechanisms to withstand salt stress. One of the key strategies is the utilization of microRNAs (miRNAs) that can influence gene regulation at the post-transcriptional stage under different environmental conditions, including salinity. Here, we have reviewed the miRNA-mediated adaptations of various plant species to salt stress and other abiotic variables. Moreover, salt responsive (SR)-miRNAs, their targets, and corresponding pathways have also been discussed. The review article concludes by suggesting that the utilization of miRNAs may be a vital strategy to generate salt tolerant crops ensuring food security in the future.

The MYB33, MYB65, and MYB101 transcription factors affect Arabidopsis and potato responses to drought by regulating the ABA signaling pathway

Drought is one of the main climate threats limiting crop production. Potato is one of the four most important food crop species worldwide and is sensitive to water shortage. The CBP80 gene was shown to affect Arabidopsis and potato responses to drought by regulating the level of microRNA159 and, consequently, the levels of the MYB33 and MYB101 transcription factors (TFs). Here, we show that three MYB TFs, MYB33, MYB65, and MYB101, are involved in plant responses to water shortage. Their downregulation in Arabidopsis causes stomatal hyposensitivity to abscisic acid (ABA), leading to reduced tolerance to drought. Transgenic Arabidopsis and potato plants overexpressing these genes, with a mutated recognition site in miR159, show hypersensitivity to ABA and relatively high tolerance to drought conditions. Thus, the MYB33, MYB65, and MYB101 genes may be potential targets for innovative breeding to obtain crops with relatively high tolerance to drought.

Real-Time Assessment of Mandarin Crop Water Stress Index

The use of plant-based indicators and other conventional means to detect the level of water stress in crops may be challenging, due to their difficulties in automation, their arduousness, and their time-consuming nature. Non-contact and non-destructive sensing methods can be used to detect the level of water stress in plants continuously and to provide automatic sensing and controls. This research aimed at determining the viability, efficiency, and swiftness in employing the commercial Workswell WIRIS Agro R infrared camera (WWARIC) in monitoring water stress and scheduling appropriate irrigation regimes in mandarin plants. The experiment used a four-by-three randomized complete block design with 80−100% FC water treatment as full field capacity and three deficit irrigation treatments at 70−75% FC, 60−65% FC, and 50−55% FC. Air temperature, canopy temperature, and vapor pressure deficits were measured and employed to deduce the empirical crop water stress index, using the Idso approach (CWSI(Idso)) as well as baseline equations to calculate non-water stress and water stressed conditions. The relative leaf water content (RLWC) of mandarin plants was also determined for the growing season. From the experiment, CWSI(Idso) and CWSI were estimated using the Workswell Wiris Agro R infrared camera (CWSIW) and showed a high correlation (R2 = 0.75 at p < 0.05) in assessing the extent of water stress in mandarin plants. The results also showed that at an altitude of 12 m above the mandarin canopy, the WWARIC was able to identify water stress using three modes (empirical, differential, and theoretical). The WWARIC’s color map feature, presented in real time, makes the camera a suitable device, as there is no need for complex computations or expert advice before determining the extent of the stress the crops are subjected to. The results prove that this novel use of the WWARIC demonstrated sufficient precision, swiftness, and intelligibility in the real-time detection of the mandarin water stress index and, accordingly, assisted in scheduling irrigation.

Seed-Encapsulation of Desiccation-Tolerant Microorganisms for the Protection of Maize from Drought: Phenotyping Effects of a New Dry Bioformulation

Droughts and high temperatures deeply affect crop production. The use of desiccation-tolerant (or xerotolerant) microorganisms able to protect plants from droughts represents a promising alternative. These xerotolerant microorganisms have previously been used to modulate plant responses and improve their tolerance to drought. In addition, these microorganisms could be stored and used in dry formats, which would improve their viability and resilience at a much lower cost than current market alternatives. In the present study we analyze the possibility of using strains of xerotolerant Actinobacteria in encapsulated format on seeds. Under this formulation, we carried out greenhouse with farming soil with maize plants. Under greenhouse conditions, the plants showed greater resistance to drought, as well as increased growth and production yield, but not as well in field trials. This alternative could represent a useful tool to improve water efficiency in crops for drought-affected areas or affected by water scarcity.

Nanomaterials coupled with microRNAs for alleviating plant stress: a new opening towards sustainable agriculture

Plant growth and development is influenced by their continuous interaction with the environment. Their cellular machinery is geared to make rapid changes for adjusting the morphology and physiology to withstand the stressful changes in their surroundings. The present scenario of climate change has however intensified the occurrence and duration of stress and this is getting reflected in terms of yield loss. A number of breeding and molecular strategies are being adopted to enhance the performance of plants under abiotic stress conditions. In this context, the use of nanomaterials is gaining momentum. Nanotechnology is a versatile field and its application has been demonstrated in almost all the existing fields of science. In the agriculture sector, the use of nanoparticles is still limited, even though it has been found to increase germination and growth, enhance physiological and biochemical activities and impact gene expression. In this review, we have summarized the use and role of nanomaterial and small non-coding RNAs in crop improvement while highlighting the potential of nanomaterial assisted eco-friendly delivery of small non-coding RNAs as an innovative strategy for mitigating the effect of abiotic stress.

Zinnia (Zinnia elegans L.) and Periwinkle (Catharanthus roseus (L.) G. Don) Responses to Salinity Stress

The study of salinity stress in irrigated floriculture can make a significant contribution to the preservation of freshwater sources. To analyze the morphological and aesthetic responses of zinnia (Zinnia elegans L.) and periwinkle (Catharanthus roseus (L.) G. Don) to different salinity stress levels, the following treatments were performed: s0 = municipal water (control), s1 = 3 dS m−1, s2 = 4.5 dS m−1, and s3 = 6 dS m−1. The growth of zinnia (flower number, plant height, branch and leaf number, total fresh and dry biomass, and root length) was linearly reduced by increasing salinity levels, while all observed periwinkle traits for the s2 salinity treatment were either equal to or greater than the control treatment (n.s.) and a further increase in salinity stress showed a significant (p < 0.01) decrease. The first flower buds on zinnia appeared with the control treatment (s0), while for periwinkle the first flower bud appeared with the s1 treatment. With regard to both zinnia and periwinkle leaf necrosis, drying and firing occurred during the third week in the s2 and s3 treatments. Zinnia proved to be sensitive to salinity, while periwinkle showed mild tolerance to salinity stress, up to 3 dS m−1.

Overexpression of the Tectona grandis TgNAC01 regulates growth, leaf senescence and confer salt stress tolerance in transgenic tobacco plants

NAC transcription factors play critical roles in xylem secondary development and in regulation of stress response in plants. NAC proteins related to secondary cell wall development were recently identified and characterized in Tectona grandis (teak), one of the hardwood trees of highest economic importance in the world. In this work, we characterized the novel TgNAC01 gene, which is involved in signaling pathways that mediate teak response to stress. Abscisic acid (ABA) increases TgNAC01 expression in teak plants. Therefore, this gene may have a role in signaling events that mediate ABA-dependent osmotic stress responsive in this plant species. Stable expression in tobacco plants showed that the TgNAC01 protein is localized in the cell nucleus. Overexpression of TgNAC01 in two out three independent transgenic tobacco lines resulted in increased growth, leaf senescence and salt tolerance compared to wild type (WT) plants. Moreover, the stress tolerance of transgenic plants was affected by levels of TgNAC01 gene expression. Water potential, gas exchange and chlorophyll fluorescence were used to determine salt stress tolerance. The 35S:TgNAC01-6 line under 300 mM NaCl stress responded with a significant increase in photosynthesis rate, stomatal conductance, transpiration and carboxylation efficiency, but lower water potential compared to WT plants. The data indicate that the TgNAC01 transcription factor acts as a transcriptional activator of the ABA-mediated regulation and induces leaf senescence.

Identification of a Negative Regulator for Salt Tolerance at Seedling Stage via a Genome-wide Association Study of Thai Rice Populations

Salt stress is a major limiting factor in crop production and yield in many regions of the world. The objective of this study was to identify the genes responsible for salt tolerance in Thai rice populations. We performed a genome-wide association study with growth traits, relative water content, and cell membrane stability at the seedling stage, and predicted 25 putative genes. Eleven of them were located within previously reported salt-tolerant QTLs (ST-QTLs). OsCRN, located outside the ST-QTLs, was selected for gene characterization using the Arabidopsis mutant line with T-DNA insertion in the orthologous gene. Mutations in the AtCRN gene led to the enhancement of salt tolerance by increasing the ability to maintain photosynthetic pigment content and relative water content, while the complemented lines with ectopic expression of OsCRN showed more susceptibility to salt stress detected by photosynthesis performance. Moreover, the salt-tolerant rice varieties showed lower expression of this gene than the susceptible rice varieties under salt stress conditions. The study concludes that by acting as a negative regulator, OsCRN plays an important role in salt tolerance in rice.

Genome-Wide Identification, Characterization and Expression Analysis of the CIPK Gene Family in Potato (Solanum tuberosum L.) and the Role of StCIPK10 in Response to Drought and Osmotic Stress

The potato (Solanum tuberosum L.), one of the most important food crops worldwide, is sensitive to environmental stresses. Sensor–responder complexes comprising calcineurin B-like (CBL) proteins and CBL-interacting protein kinases (CIPKs) not only modulate plant growth and development but also mediate numerous stress responses. Here, using a Hidden Markov Model and BLAST searches, 27 CIPK genes were identified in potato and divided into five groups by phylogenetic analysis and into two clades (intron-poor and intron-rich) by gene structure analysis. Quantitative reverse-transcription PCR (qRT-PCR) assays revealed that StCIPK genes play important roles in plant growth, development and abiotic stress tolerance. Up-regulated expression of StCIPK10 was significantly induced by drought, PEG6000 and ABA. StCIPK10 enhances both the ability of potato to scavenge reactive oxygen species and the content of corresponding osmoregulation substances, thereby strengthening tolerance to drought and osmotic stress. StCIPK10 is located at the intersection between the abscisic acid and abiotic stress signaling pathways, which control both root growth and stomatal closure in potato. In addition, StCIPK10 interacts with StCBL1, StCBL4, StCBL6, StCBL7, StCBL8, StCBL11 and StCBL12, and is specifically recruited to the plasma membrane by StCBL11.

Modulation of the toxic effects of zinc oxide nanoparticles by exogenous salicylic acid pretreatment in Chenopodium murale L

Due to many uses of zinc oxide nanoparticles (ZnO NPs) in various industries, the release of these particles in the environment and their effects on living organisms is inevitable. In this study, the role of salicylic acid (SA) pretreatments in modulating the toxicity of ZnO NPs was investigated using a hydroponic system. After pretreatment with different concentrations of SA (0, 25, 75, and 150 μM), Chenopodium murale plants were exposed to ZnO NPs (50 mg L^-1). The results showed that exogenous SA increased the length, weight, chlorophyll, proline, starch, and soluble sugars in the plants. Besides, SA pretreatments improved water status in the plants treated with ZnO NPs. In SA-pretreated plants, increased activity of catalase (CAT), guaiacol peroxidase (GPX), and superoxide dismutase (SOD) was associated with a decline in electrolyte leakage (EL %) and membrane peroxidation. Under NPs stress, SA pretreatments increased the content of phenolic compounds by increasing the activity of phenylalanine ammonia-lyase (PAL). Exogenous SA reduced the translocation of larger amounts of Zn to the shoots, with more accumulation in the roots. This result can be used to produce healthy food from plants grown in environments contaminated with nanoparticles. It seems that all concentrations of SA reduced the symptoms of ZnO NPs toxicity in the plant by strengthening the function of the antioxidant system and increasing the content of some metabolites. Findings also suggest that SA pretreatment can compensate for the growth reduction caused by ZnO NPs.

Non-Coding RNAs in Response to Drought Stress

Drought stress causes changes in the morphological, physiological, biochemical and molecular characteristics of plants. The response to drought in different plants may vary from avoidance, tolerance and escape to recovery from stress. This response is genetically programmed and regulated in a very complex yet synchronized manner. The crucial genetic regulations mediated by non-coding RNAs (ncRNAs) have emerged as game-changers in modulating the plant responses to drought and other abiotic stresses. The ncRNAs interact with their targets to form potentially subtle regulatory networks that control multiple genes to determine the overall response of plants. Many long and small drought-responsive ncRNAs have been identified and characterized in different plant varieties. The miRNA-based research is better documented, while lncRNA and transposon-derived RNAs are relatively new, and their cellular role is beginning to be understood. In this review, we have compiled the information on the categorization of non-coding RNAs based on their biogenesis and function. We also discuss the available literature on the role of long and small non-coding RNAs in mitigating drought stress in plants.

Limoniastrum guyonianum behavior under seasonal conditions fluctuations of Sabkha Aïn Maïder (Tunisia)

In Sabkha biotope, several environmental factors (i.e., salinity, drought, temperature, etc.) especially during dry season affect halophytes developments. To cope with these harmful conditions, halophytes use multiple mechanisms of adaptations. In this study, we focused on the effect of environmental condition changes over a year in the Sabkha of Aïn Maïder (Medenine - Tunisia) on the physiological and biochemical behavior of Limoniastrum guyonianum using a modeling approach. Our study showed that the model depicted well (R² > 0.75) the monthly fluctuations of the studied parameters in this habitat. During the dry period (June to September), the salinity of the soil increased remarkably (high level of EC and Na⁺ content), resulting in high Na⁺ content in the aerial parts followed by a nutrient deficiency in K⁺, Ca²⁺, and Mg²⁺. As a result of this disruption, L. guyonianum decreased its water potential to more negative values to maintain osmotic potential using inorganic osmolytes (i.e., Na⁺) and organic osmolytes (i.e., sugars: sucrose, fructose, glucose, and xylitol, and organic acids: citric and malic acids). In addition, CO₂ assimilation rate, stomatal conductance, transpiration rate, and photosynthetic pigments decreased significantly with increasing salinity. The phenolic compounds contents and the antioxidant activity increased significantly in the dry period as a result of increased levels of H₂O₂ and lipid peroxidation. This increase was highly correlated with soil salinity and air temperature. The maintenance of tissue hydration (i.e., moderate decrease of relative water content), the accumulation of sugars and organic acids, the enhancement of phenolic compounds amounts, and the increase of antioxidant activity during the dry period suggest that L. guyonianum possesses an efficient tolerance mechanism that allows the plant to withstand the seasonal fluctuations of climatic conditions in its natural biotope.

Ground-Based Hyperspectral Remote Sensing for Estimating Water Stress in Tomato Growth in Sandy Loam and Silty Loam Soils

Drought and water scarcity due to global warming, climate change, and social development have been the most death-defying threat to global agriculture production for the optimization of water and food security. Reflectance indices obtained by an Analytical Spectral Device (ASD) Spec 4 hyperspectral spectrometer from tomato growth in two soil texture types exposed to four water stress levels (70-100% FC, 60-70% FC, 50-60% FC, and 40-50% FC) was deployed to schedule irrigation and management of crops' water stress. The treatments were replicated four times in a randomized complete block design (RCBD) in a 2 × 4 factorial experiment. Water stress treatments were monitored with Time Domain Reflectometer (TDR) every 12 h before and after irrigation to maintain soil water content at the desired (FC%). Soil electrical conductivity (Ec) was measured daily throughout the growth cycle of tomatoes in both soil types. Ec was revealing a strong correlation with water stress at R² above 0.95 p < 0.001. Yield was measured at the end of the end of the growing season. The results revealed that yield had a high correlation with water stress at R² = 0.9758 and 0.9816 p < 0.01 for sandy loam and silty loam soils, respectively. Leaf temperature (LT °C), relative leaf water content (RLWC), leaf chlorophyll content (LCC), Leaf area index (LAI), were measured at each growth stage at the same time spectral reflectance data were measured throughout the growth period. Spectral reflectance indices used were grouped into three: (1) greenness vegetative indices; (2) water overtone vegetation indices; (3) Photochemical Reflectance Index centered at 570 nm (PRI₅₇₀), and normalized PRI (PRInorm). These reflectance indices were strongly correlated with all four water stress indicators and yield. The results revealed that NDVI, RDVI, WI, NDWI, NDWI₁₆₄₀, PRI₅₇₀, and PRInorm were the most sensitive indices for estimating crop water stress at each growth stage in both sandy loam and silty loam soils at R² above 0.35. This study recounts the depth of 858 to 1640 nm band absorption to water stress estimation, comparing it to other band depths to give an insight into the usefulness of ground-based hyperspectral reflectance indices for assessing crop water stress at different growth stages in different soil types.

Early transcriptional responses in Solanum peruvianum and Solanum lycopersicum account for different acclimation processes during water scarcity events

Cultivated tomato Solanum lycopersicum (Slyc) is sensitive to water shortages, while its wild relative Solanum peruvianum L. (Sper), an herbaceous perennial small shrub, can grow under water scarcity and soil salinity environments. Plastic Sper modifies the plant architecture when suffering from drought, which is mediated by the replacement of leaf organs, among other changes. The early events that trigger acclimation and improve these morphological traits are unknown. In this study, a physiological and transcriptomic approach was used to understand the processes that differentiate the response in Slyc and Sper in the context of acclimation to stress and future consequences for plant architecture. In this regard, moderate (MD) and severe drought (SD) were imposed, mediating PEG treatments. The results showed a reduction in water and osmotic potential during stress, which correlated with the upregulation of sugar and proline metabolism-related genes. Additionally, the senescence-related genes FTSH6 protease and asparagine synthase were highly induced in both species. However, GO categories such as "protein ubiquitination" or "endopeptidase inhibitor activity" were differentially enriched in Sper and Slyc, respectively. Genes related to polyamine biosynthesis were induced, while several cyclins and kinetin were downregulated in Sper under drought treatments. Repression of photosynthesis-related genes was correlated with a higher reduction in the electron transport rate in Slyc than in Sper. Additionally, transcription factors from the ERF, WRKY and NAC families were commonly induced in Sper. Although some similar responses were induced in both species under drought stress, many important changes were detected to be differentially induced. This suggests that different pathways dictate the strategies to address the early response to drought and the consequent episodes in the acclimation process in both tomato species.

Biochemical and Molecular Effects Induced by Triacontanol in Acquired Tolerance of Rice to Drought Stress

To assess the effect of triacontanol (TRIA) on rice plants grown under normal or drought conditions, rice seeds were presoaked in TRIA (35 ppm) for two hours. After 20 days of sowing, rice seedlings developed from TRIA-treated or untreated seeds were subjected to drought stress. After 10 days of plant exposure to drought stress, data of major growth attributes and the content of photosynthetic pigments were recorded. Moreover, the effect of drought stress on stomatal conductance and the photochemical efficiency of PSII (Fv/Fm) were followed. The data obtained indicated that the species of rice (Oryza sativa L.) cultivar Giza 177 under investigation was sensitive to drought stress where there were significant decreases in the fresh and dry weights of shoots and roots and in stomatal conductance, as well as in the content of chlorophyll a, chlorophyll b, and carotenoids. Seed priming with TRIA enhanced both growth and acquired plant tolerance to drought stress. Thus, TRIA via the enhancement of stomatal conductance through the regulation of stomatal closure, the rate of water loss, ABA metabolism, the accumulation of osmolytes, and the regulation of aquaporins genes improved the water status of plants grown under water scarcity. Moreover, TRIA via increasing the content of free amino acids and sugars under drought stress may increase the chance of plant tissues to retain more water under scarcity conditions.

Response to water deficit of semi-desert wild potato Solanum kurtzianum genotypes collected from different altitudes

Drought-sensitive crops are threatened as a consequence of limited available water due to climate change. The cultivated potato (Solanum tuberosum) is susceptible to drought and within its wild relative species, Solanum kurtzianum is the Argentinian wild potato species best adapted to arid conditions. However, its physiological responses to water deficit (WD) are still missing. Within the distribution of S. kurtzianum, genotypes could be adapted to differential precipitation regimes. The aim of this work was to evaluate responses of three S. kurtzianum genotypes collected at 1100 (G1), 1900 (G2) and 2100 m a.s.l. (G3) to moderate and severe WD. Treatments were imposed since flowering and lasted 36 days. Yield components, morpho-physiological and biochemical responses; and phenotypic plasticity were evaluated. The three genotypes presented mechanisms to tolerate both WD treatments. G1 presented the lowest yield reduction under moderate WD, mainly through a rapid stomatal closure and a modest vegetative growth. The differences among genotypes suggest that local adaptation is taking place within its natural habitat. Also, G2 presented environmentally induced shifts in plasticity for stomatal length and carotenoids, suggesting that phenotypic plasticity has a role in acclimation of plants to WD until selection works.

Arabidopsis ACINUS is O-glycosylated and regulates transcription and alternative splicing of regulators of reproductive transitions

O-GlcNAc modification plays important roles in metabolic regulation of cellular status. Two homologs of O-GlcNAc transferase, SECRET AGENT (SEC) and SPINDLY (SPY), which have O-GlcNAc and O-fucosyl transferase activities, respectively, are essential in Arabidopsis but have largely unknown cellular targets. Here we show that AtACINUS is O-GlcNAcylated and O-fucosylated and mediates regulation of transcription, alternative splicing (AS), and developmental transitions. Knocking-out both AtACINUS and its distant paralog AtPININ causes severe growth defects including dwarfism, delayed seed germination and flowering, and abscisic acid (ABA) hypersensitivity. Transcriptomic and protein-DNA/RNA interaction analyses demonstrate that AtACINUS represses transcription of the flowering repressor FLC and mediates AS of ABH1 and HAB1, two negative regulators of ABA signaling. Proteomic analyses show AtACINUS's O-GlcNAcylation, O-fucosylation, and association with splicing factors, chromatin remodelers, and transcriptional regulators. Some AtACINUS/AtPININ-dependent AS events are altered in the sec and spy mutants, demonstrating a function of O-glycosylation in regulating alternative RNA splicing.

Glutathione Restores Hg-Induced Morpho-Physiological Retardations by Inducing Phytochelatin and Oxidative Defense in Alfalfa

Simple Summary

An ecofriendly approach to mitigate mercury (Hg) toxicity in alfalfa, one of the important forage crops, is highly desirable for environmental sustainability. In this study, the exogenous glutathione (GSH) substantially improved the morphological hindrance and photosynthesis inefficiency in Hg-exposed alfalfa plants. In addition, the Fe and S status of Cd-toxic alfalfa was restored due to GSH supplementation. Interestingly, GSH applied to Hg-exposed plants showed elevated Hg concentration in roots resulted in a substantial deposition of Hg in the root cell wall due to the upregulation of MsPCS1 and MsGSH1 genes in roots. It implies that GSH induces PC accumulation in roots enabling excess Hg bound to the cell wall, thereby limiting the transport of Hg to the aerial part of alfalfa. In silico analysis further suggests a conserved motif linked to the phytochelatin synthase domain (CL0125). In addition, GSH induced the GSH concentration and GR activity in protecting alfalfa plants from Hg-induced oxidative damage. These findings can be useful to formulate GSH-based fertilizer or to develop Hg-tolerant alfalfa plants.

Abstract

Mercury (Hg) is toxic to plants, but the effect of glutathione in Hg alleviation was never studied in alfalfa, an important forage crop. In this study, Hg toxicity showed morphological retardation, chlorophyll reduction, and PSII inefficiency, which was restored due to GSH supplementation in alfalfa plants treated with Hg. Results showed a significant increase of Hg, but Fe and S concentrations substantially decreased in root and shoot accompanied by the downregulation of Fe (MsIRT1) and S (MsSultr1;2 and MsSultr1;3) transporters in roots of Hg-toxic alfalfa. However, GSH caused a significant decrease of Hg in the shoot, while the root Hg level substantially increased, accompanied by the restoration of Fe and S status, relative to Hg-stressed alfalfa. The subcellular analysis showed a substantial deposition of Hg in the root cell wall accompanied by the increased GSH and PC and the upregulation of MsPCS1 and MsGSH1 genes in roots. It suggests the involvement of GSH in triggering PC accumulation, causing excess Hg bound to the cell wall of the root, thereby reducing Hg translocation in alfalfa. Bioinformatics analysis showed that the MsPCS1 protein demonstrated one common conserved motif linked to the phytochelatin synthase domain (CL0125) with MtPCS1 and AtMCS1 homologs. These in silico analysis further confirmed the detoxification role of MsPCS1 induced by GSH in Hg-toxic alfalfa. Additionally, GSH induces GSH and GR activity to counteract oxidative injuries provoked by Hg-induced H₂O₂ and lipid peroxidation. These findings may provide valuable knowledge to popularize GSH-derived fertilizer or to develop Hg-free alfalfa or other forage plants.

Barley microRNAs as metabolic sensors for soil nitrogen availability

Barley (Hordeum vulgare) is one of the most important crops in the world, ranking 4th in the worldwide production. Crop breeders are facing increasing environmental obstacles in the field, such as drought, salinity but also toxic over fertilization which not only impacts quality of the grain but also an yield. One of the most prevalent mechanisms of gene expression regulation in plants is microRNA-mediated silencing of target genes. We identified 13 barley microRNAs and 2 microRNAs* that are nitrogen excess responsive. Four microRNAs respond only in root, eight microRNAs only in shoot and one displays broad response in roots and shoots. We demonstrate that 2 microRNAs* are induced in barley shoot by nitrogen excess. For all microRNAs we identified putative target genes and confirmed microRNA-guided cleavage sites for ten out of thirteen mRNAs. None of the identified microRNAs or their target genes is known as nitrogen excess responsive. Analysis of expression pattern of thirteen target mRNAs and their cognate microRNAs showed expected correlations of their levels. The plant microRNAs analyzed are also known to respond to nitrogen deprivation and exhibit the opposite expression pattern when nitrogen excess/deficiency conditions are compared. Thus, they can be regarded as metabolic sensors of the regulation of nitrogen homeostasis in plants.

Assessment of ZnO-NPs toxicity in maize: An integrative microRNAomic approach

Rapid expansion of nanotechnology and indiscriminate discharge of metal oxide nanoparticles (NPs) into the environment pose a serious hazard to the ecological receptors including plants. To better understand the role of miRNAs in ZnO-NPs stress adaptation, two small RNA libraries were prepared from control and ZnO-NPs (800 ppm, <50 nm particle size) stressed maize leaves. Meager performance of ZnO-NPs treated seedlings was associated with elevated tissue zinc accumulation, enhanced ROS generation, loss of root cell viability, increased foliar MDA content, decrease in chlorophyll and carotenoids contents. Deep sequencing identified 3 (2 known and 1 novel) up- and 77 (73 known and 4 novel) down-regulated miRNAs from ZnO-NPs challenged leaves. GO analysis reveals that potential targets of ZnO-NPs responsive miRNAs regulate diverse biological processes viz. plant growth and development (miR159f-3p, zma_18), ROS homeostasis (miR156b, miR166l), heavy metal transport and detoxification (miR444a, miR167c-3p), photosynthesis (miR171b) etc. Up-regulation of SCARECROW 6 in ZnO-NPs treated leaves might be responsible for suppression of chlorophyll biosynthesis leading to yellowing of leaves. miR156b.1 mediated up-regulation of CALLOSE SYNTHASE also does not give much protection against ZnO-NPs treatment. Taken together, the findings shed light on the miRNA-guided stress regulatory networks involved in plant adaptive responses to ZnO-NPs stress.

Animal wastes as fertilizers enhance growth of young walnut trees under soil drought conditions

BACKGROUND

Using nutrient-rich animal wastes as organic fertilizers in agricultural practices is a sustainable method for soil amendment and avoiding environmental pollution. In order to evaluate their practical effect, we applied different proportions of animal waste as fertilizers to wet or dry soils that were either planted or not planted with young walnut trees.

RESULTS

The results showed that animal waste could increase soil C accumulation and carbon to nitrogen (C/N) ratio and reduce soil organic nitrogen and total nitrogen contents as well as the nitrogen to phosphorus (N/P) ratio in the planted group soil. This framework of soil C and N composition (a high C/N ratio) resulted in high N and Mg contents as well as high Cu and Zn contents in the leaves of the young trees as well as a high dry matter weight/leaf N ratio, causing increased leaf photosynthesis, reduced transpiration and relatively high water use efficiency under soil drought conditions. Also, animal wastes as fertilizers caused the branching of walnut to switch from elongation growth to thickening growth under soil drought conditions.

CONCLUSIONS

Principal component analysis and redundancy analysis demonstrated the mechanism by which the soil C/N ratio mediates the flux of available nutrients from the soil to the plant and thereby regulates plant dry matter accumulation and branching architecture under soil drought conditions. The results of this study provide new insights into the improvement of hilly soils using animal waste. © 2020 Society of Chemical Industry.

NCBP1 promotes the development of lung adenocarcinoma through up-regulation of CUL4B

Lung cancer is the most frequent cancer type and is the leading cause of tumour‐associated deaths worldwide. Nuclear cap‐binding protein 1 (NCBP1) is necessary for capped RNA processing and intracellular localization. It has been reported that silencing of NCBP1 resulted in cell growth reduction in HeLa cells. Nevertheless, its clinical significance and underlying molecular mechanisms in non–small‐cell lung cancer remain unclear. In this study, we found that NCBP1 was significantly overexpressed in lung cancer tissues and several lung cancer cell lines. Through knockdown and overexpression experiments, we showed that NCBP1 promoted lung cancer cell growth, wound healing ability, migration and epithelial‐mesenchymal transition. Mechanistically, we found that cullin 4B (CUL4B) was a downstream target gene of NCBP1 in NSCLC. NCBP1 up‐regulated CUL4B expression via interaction with nuclear cap‐binding protein 3 (NCBP3). CUL4B silencing significantly reversed NCBP1‐induced tumorigenesis in vitro. Based on these findings, we propose a model involving the NCBP1‐NCBP3‐CUL4B oncoprotein axis, providing novel insight into how CUL4B is activated and contributes to LUAD progression.

Biology and Function of miR159 in Plants

MicroR159 (miR159) is ancient, being present in the majority of land plants where it targets a class of regulatory genes called GAMYB or GAMYB-like via highly conserved miR159-binding sites. These GAMYB genes encode R2R3 MYB domain transcription factors that transduce the gibberellin (GA) signal in the seed aleurone and the anther tapetum. Here, GAMYB plays a conserved role in promoting the programmed cell death of these tissues, where miR159 function appears weak. By contrast, GAMYB is not involved in GA-signaling in vegetative tissues, but rather its expression is deleterious, leading to the inhibition of growth and development. Here, the major function of miR159 is to mediate strong silencing of GAMYB to enable normal growth. Highlighting this requirement of strong silencing are conserved RNA secondary structures associated with the miR159-binding site in GAMYB mRNA that promotes miR159-mediated repression. Although the miR159-GAMYB pathway in vegetative tissues has been implicated in a number of different functions, presently no conserved role for this pathway has emerged. We will review the current knowledge of the different proposed functions of miR159, and how this ancient pathway has been used as a model to help form our understanding of miRNA biology in plants.

miR403a and SA Are Involved in NbAGO2 Mediated Antiviral Defenses Against TMV Infection in Nicotiana benthamiana

RNAi (RNA interference) is an important defense response against virus infection in plants. The core machinery of the RNAi pathway in plants include DCL (Dicer Like), AGO (Argonaute) and RdRp (RNA dependent RNA polymerase). Although involvement of these RNAi components in virus infection responses was demonstrated in Arabidopsis thaliana, their contribution to antiviral immunity in Nicotiana benthamiana, a model plant for plant-pathogen interaction studies, is not well understood. In this study, we investigated the role of N. benthamiana NbAGO2 gene against TMV (Tomato mosaic virus) infection. Silencing of NbAGO2 by transient expression of an hpRNA construct recovered GFP (Green fluorescent protein) expression in GFP-silenced plant, demonstrating that NbAGO2 participated in RNAi process in N. benthamiana. Expression of NbAGO2 was transcriptionally induced by both MeSA (Methylsalicylate acid) treatment and TMV infection. Down-regulation of NbAGO2 gene by amiR-NbAGO2 transient expression compromised plant resistance against TMV infection. Inhibition of endogenous miR403a, a predicted regulatory microRNA of NbAGO2, reduced TMV infection. Our study provides evidence for the antiviral role of NbAGO2 against a Tobamovirus family virus TMV in N. benthamiana, and SA (Salicylic acid) mediates this by induction of NbAGO2 expression upon TMV infection. Our data also highlighted that miR403a was involved in TMV defense by regulation of target NbAGO2 gene in N. Benthamiana.

Expression of miR159 Is Altered in Tomato Plants Undergoing Drought Stress

In a scenario of global climate change, water scarcity is a major threat for agriculture, severely limiting crop yields. Therefore, alternatives are urgently needed for improving plant adaptation to drought stress. Among them, gene expression reprogramming by microRNAs (miRNAs) might offer a biotechnologically sound strategy. Drought-responsive miRNAs have been reported in many plant species, and some of them are known to participate in complex regulatory networks via their regulation of transcription factors involved in water stress signaling. We explored the role of miR159 in the response of Solanum lycopersicum Mill. plants to drought stress by analyzing the expression of sly-miR159 and its target SlMYB transcription factor genes in tomato plants of cv. Ailsa Craig grown in deprived water conditions or in response to mechanical damage caused by the Colorado potato beetle, a devastating insect pest of Solanaceae plants. Results showed that sly-miR159 regulatory function in the tomato plants response to distinct stresses might be mediated by differential stress-specific MYB transcription factor targeting. sly-miR159 targeting of SlMYB33 transcription factor transcript correlated with accumulation of the osmoprotective compounds proline and putrescine, which promote drought tolerance. This highlights the potential role of sly-miR159 in tomato plants’ adaptation to water deficit conditions.

Transcriptome Profiling Reveals Effects of Drought Stress on Gene Expression in Diploid Potato Genotype P3-198

Potato (Solanum tuberosum L.) is one of the three most important food crops worldwide; however, it is strongly affected by drought stress. The precise molecular mechanisms of drought stress response in potato are not very well understood. The diploid potato genotype P3-198 has been verified to be highly resistant to drought stress. Here, a time-course experiment was performed to identify drought resistance response genes in P3-198 under polyethylene glycol (PEG)-induced stress using RNA-sequencing. A total of 1665 differentially expressed genes (DEGs) were specifically identified, and based on gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the transcription factor activity, protein kinase activity, and the plant hormone signal transduction process were significantly enriched. Annotation revealed that these DEGs mainly encode transcription factors, protein kinases, and proteins related to redox regulation, carbohydrate metabolism, and osmotic adjustment. In particular, genes encoding abscisic acid (ABA)-dependent signaling molecules were significantly differentially expressed, which revealed the important roles of the ABA-dependent signaling pathway in the early response of P3-198 to drought stress. Quantitative real-time PCR experimental verification confirmed the differential expression of genes in the drought resistance signaling pathway. Our results provide valuable information for understanding potato drought-resistance mechanisms, and also enrich the gene resources available for drought-resistant potato breeding.

Methodology of Drought Stress Research: Experimental Setup and Physiological Characterization

Drought is one of the major stress factors affecting the growth and development of plants. In this context, drought-related losses of crop plant productivity impede sustainable agriculture all over the world. In general, plants respond to water deficits by multiple physiological and metabolic adaptations at the molecular, cellular, and organism levels. To understand the underlying mechanisms of drought tolerance, adequate stress models and arrays of reliable stress markers are required. Therefore, in this review we comprehensively address currently available models of drought stress, based on culturing plants in soil, hydroponically, or in agar culture, and critically discuss advantages and limitations of each design. We also address the methodology of drought stress characterization and discuss it in the context of real experimental approaches. Further, we highlight the trends of methodological developments in drought stress research, i.e., complementing conventional tests with quantification of phytohormones and reactive oxygen species (ROS), measuring antioxidant enzyme activities, and comprehensively profiling transcriptome, proteome, and metabolome.

Ascophyllum nodosum extract mitigates salinity stress in Arabidopsis thaliana by modulating the expression of miRNA involved in stress tolerance and nutrient acquisition

Ascophyllum nodosum extract (ANE) contains bioactive compounds that improve the growth of Arabidopsis in experimentally-induced saline conditions; however, the molecular mechanisms through which ANE elicits tolerance to salinity remain largely unexplored. Micro RNAs (miRNAs) are key regulators of gene expression, playing crucial roles in plant growth, development, and stress tolerance. Next generation sequencing of miRNAs from leaves of control Arabidopsis and from plants subjected to three treatments (ANE, NaCl and ANE+NaCl) was used to identify ANE-responsive miRNA in the absence and presence of saline conditions. Differential gene expression analysis revealed that ANE had a strong effect on miRNAs expression in both conditions. In the presence of salinity, ANE tended to reduce the up-regulation or the down-regulation trend induced caused by NaCl in miRNAs such as ath-miR396a-5p, ath-miR399, ath-miR2111b and ath-miR827. To further uncover the effects of ANE, the expression of several target genes of a number of ANE-responsive miRNAs was analyzed by qPCR. NaCl, but not ANE, down-regulated miR396a-5p, which negatively regulated the expression of AtGRF7 leading to a higher expression of AtDREB2a and AtRD29 in the presence of ANE+NaCl, as compared to ANE alone. ANE+NaCl initially reduced and then enhanced the expression of ath-miR169g-5p, while the expression of the target genes AtNFYA1 and ATNFYA2, known to be involved in the salinity tolerance mechanism, was increased as compared to ANE or to NaCl treatments. ANE and ANE+NaCl modified the expression of ath-miR399, ath-miR827, ath-miR2111b, and their target genes AtUBC24, AtWAK2, AtSYG1 and At3g27150, suggesting a role of ANE in phosphate homeostasis. In vivo and in vitro experiments confirmed the improved growth of Arabidopsis in presence of ANE, in saline conditions and in phosphate-deprived medium, further substantiating the influence of ANE on a variety of essential physiological processes in Arabidopsis including salinity tolerance and phosphate uptake.

The maize lilliputian1 (lil1) gene, encoding a brassinosteroid cytochrome P450 C-6 oxidase, is involved in plant growth and drought response

BACKGROUND AND AIMS

Brassinosteroids (BRs) are plant hormones involved in many developmental processes as well as in plant-environment interactions. Their role was investigated in this study through the analysis of lilliputian1-1 (lil1-1), a dwarf mutant impaired in BR biosynthesis in maize (Zea mays).

METHODS

We isolated lil1-1 through transposon tagging in maize. The action of lil1 was investigated through morphological and genetic analysis. Moreover, by comparing lil1-1 mutant and wild-type individuals grown under drought stress, the effect of BR reduction on the response to drought stress was examined.

KEY RESULTS

lil1-1 is a novel allele of the brassinosteroid-deficient dwarf1 (brd1) gene, encoding a brassinosteroid C-6 oxidase. We show in this study that lil1 is epistatic to nana plant1 (na1), a BR gene involved in earlier steps of the pathway. The lill-1 mutation causes alteration in the root gravitropic response, leaf epidermal cell density, epicuticular wax deposition and seedling adaptation to water scarcity conditions.

CONCLUSIONS

Lack of active BR molecules in maize causes a pleiotropic effect on plant development and improves seedling tolerance of drought. BR-deficient maize mutants can thus be instrumental in unravelling novel mechanisms on which plant adaptations to abiotic stress are based.

A Role of U12 Intron in Proper Pre-mRNA Splicing of Plant Cap Binding Protein 20 Genes

The nuclear cap-binding complex (CBC) is composed of two cap-binding proteins: CBP20 and CBP80. The CBP20 gene structure is highly conserved across land plant species. All studied CBP20 genes contain eight exons and seven introns, with the fourth intron belonging to the U12 class. This highly conserved U12 intron always divides the plant CBP20 gene into two parts: one part encodes the core domain containing the RNA binding domain (RBD), and the second part encodes the tail domain with a nuclear localization signal (NLS). In this study, we investigate the importance of the U12 intron in the Arabidopsis thaliana CBP20 gene by moving it to different intron locations of the gene. Relocation of the U12 intron resulted in a significant decrease in the U12 intron splicing efficiency and the accumulation of wrongly processed transcripts. These results suggest that moving the U12 intron to any other position of the A. thaliana CBP20 gene disturbs splicing, leading to substantial downregulation of the level of properly spliced mRNA and CBP20 protein. Moreover, the replacement of the U12 intron with a U2 intron leads to undesired alternative splicing events, indicating that the proper localization of the U12 intron in the CBP20 gene secures correct CBP20 pre-mRNA maturation and CBP20 protein levels in a plant. Surprisingly, our results also show that the efficiency of U12 splicing depends on intron length. In conclusion, our study emphasizes the importance of proper U12 intron localization in plant CBP20 genes for correct pre-mRNA processing.

Genomewide identification of genes involved in the potato response to drought indicates functional evolutionary conservation with Arabidopsis plants

Potato is one of the four most important food crop plants worldwide and is strongly affected by drought. The following two pairs of potato cultivars, which are related in ancestry but show different drought tolerances, were chosen for comparative gene expression studies: Gwiazda/Oberon and Tajfun/Owacja. Comparative RNA-seq analyses of gene expression differences in the transcriptomes obtained from drought-tolerant versus drought-sensitive plants during water shortage conditions were performed. The 23 top-ranking genes were selected, 22 of which are described here as novel potato drought-responsive genes. Moreover, all but one of the potato genes selected have homologues in the Arabidopsis genome. Of the seven tested A. thaliana mutants with altered expression of the selected homologous genes, compared to the wild-type Arabidopsis plants, six showed an improved tolerance to drought. These genes encode carbohydrate transporter, mitogen-activated protein kinase kinase kinase 15 (MAPKKK15), serine carboxypeptidase-like 19 protein (SCPL19), armadillo/beta-catenin-like repeat-containing protein, high-affinity nitrate transporter 2.7 and nonspecific lipid transfer protein type 2 (nsLPT). The evolutionary conservation of the functions of the selected genes in the plant response to drought confirms the importance of these identified potato genes in the ability of plants to cope with water shortage conditions. Knowledge regarding these gene functions can be used to generate potato cultivars that are resistant to unfavourable conditions. The approach used in this work and the obtained results allowed for the identification of new players in the plant response to drought.

Mutation in HvCBP20 (Cap Binding Protein 20) Adapts Barley to Drought Stress at Phenotypic and Transcriptomic Levels

CBP20 (Cap-Binding Protein 20) encodes a small subunit of the cap-binding complex (CBC), which is involved in the conserved cell processes related to RNA metabolism in plants and, simultaneously, engaged in the signaling network of drought response, which is dependent on ABA. Here, we report the enhanced tolerance to drought stress of barley mutant in the HvCBP20 gene manifested at the morphological, physiological, and transcriptomic levels. Physiological analyses revealed differences between the hvcbp20.ab mutant and its WT in response to a water deficiency. The mutant exhibited a higher relative water content (RWC), a lower stomatal conductance and changed epidermal pattern compared to the WT after drought stress. Transcriptome analysis using the Agilent Barley Microarray integrated with observed phenotypic traits allowed to conclude that the hvcbp20.ab mutant exhibited better fitness to stress conditions by its much more efficient and earlier activation of stress-preventing mechanisms. The network hubs involved in the adjustment of hvcbp20.ab mutant to the drought conditions were proposed. These results enabled to make a significant progress in understanding the role of CBP20 in the drought stress response.

Antiviral Roles of Abscisic Acid in Plants

Abscisic acid (ABA) is a key hormone involved in tuning responses to several abiotic stresses and also has remarkable impacts on plant defense against various pathogens. The roles of ABA in plant defense against bacteria and fungi are multifaceted, inducing or reducing defense responses depending on its time of action. However, ABA induces different resistance mechanisms to viruses regardless of the induction time. Recent studies have linked ABA to the antiviral silencing pathway, which interferes with virus accumulation, and the micro RNA (miRNA) pathway through which ABA affects the maturation and stability of miRNAs. ABA also induces callose deposition at plasmodesmata, a mechanism that limits viral cell-to-cell movement. Bamboo mosaic virus (BaMV) is a member of the potexvirus group and is one of the most studied viruses in terms of the effects of ABA on its accumulation and resistance. In this review, we summarize how ABA interferes with the accumulation and movement of BaMV and other viruses. We also highlight aspects of ABA that may have an effect on other types of resistance and that require further investigation.

Plant Responses to Brief Touching: A Mechanism for Early Neighbour Detection?

In natural habitats plants can be exposed to brief and light contact with neighbouring plants. This mechanical stimulus may represent a cue that induces responses to nearby plants. However, little is known about the effect of touching on plant growth and interaction with insect herbivores. To simulate contact between plants, a soft brush was used to apply light and brief mechanical stimuli to terminal leaves of potato Solanum tuberosum L. The number of non-glandular trichomes on the leaf surface was counted on images made by light microscope while glandular trichomes and pavement cells were counted on images made under scanning electronic microscope. Volatile compounds were identified and quantified using coupled gas chromatography-mass spectrometry (GC-MS). Treated plants changed their pattern of biomass distribution; they had lower stem mass fraction and higher branch and leaf mass fraction than untouched plants. Size, weight and number of tubers were not significantly affected. Touching did not cause trichome damage nor change their total number on touched terminal leaves. However, on primary leaves the number of glandular trichomes and pavement cells was significantly increased. Touching altered the volatile emission of treated plants; they released higher quantities of the sesquiterpenes (E)-β-caryophyllene, germacrene D-4-ol and (E)-nerolidol, and lower quantities of the terpenes (E)-ocimene and linalool, indicating a systemic effect of the treatment. The odour of touched plants was significantly less preferred by the aphids Macrosiphum euphorbiae and Myzus persicae compared to odour of untouched plants. The results suggest that light contact may have a potential role in the detection of neighbouring plants and may affect plant-insect interactions.