Drought Stress Tolerance In Rice Research Articles

The Promising B-Type Response Regulator hst1 Gene Provides Multiple High Temperature and Drought Stress Tolerance in Rice.

High temperatures, drought, and salt stresses severely inhibit plant growth and production due to the effects of climate change. The Arabidopsis ARR1, ARR10, and ARR12 genes were identified as negative salt and drought stress regulators. However, in rice, the tolerance capacity of the hst1 gene, which is orthologous to the ARR1, ARR10, and ARR12 genes, to drought and multiple high temperature and drought stresses remains unknown. At the seedling and reproductive stages, we investigated the drought (DS) high temperature (HT) and multiple high temperature and drought stress (HT+DS) tolerance capacity of the YNU31-2-4 (YNU) genotype, which carries the hst1 gene, and its nearest genomic relative Sister Line (SL), which has a 99% identical genome without the hst1 gene. At the seedling stage, YNU demonstrated greater growth, photosynthesis, antioxidant enzyme activity, and decreased ROS accumulation under multiple HT+DS conditions. The YNU genotype also demonstrated improved yield potential and grain quality due to higher antioxidant enzyme activity and lower ROS generation throughout the reproductive stage under multiple HT+DS settings. Furthermore, for the first time, we discovered that the B-type response regulator hst1 gene controls ROS generation and antioxidant enzyme activities by regulating upstream and downstream genes to overcome yield reduction under multiple high temperatures and drought stress. This insight will help us to better understand the mechanisms of high temperature and drought stress tolerance in rice, as well as the evolution of tolerant crops that can survive increased salinity to provide food security during climate change.

Exogenous melatonin induces salt and drought stress tolerance in rice by promoting plant growth and defense system

Due to global climate change, crops are certainly confronted with a lot of abiotic and biotic stress factors during their growth that cause a serious threat to their development and overall productivity. Among different abiotic stresses, salt and drought are considered the most devastating stressors with serious impact on crop’s yield stability. Here, the current study aimed to elucidate how melatonin works in regulating plant biomass, oxidative stress, antioxidant defense system, as well as the expression of genes related to salt and drought stress in rice plants. Eight groups of rice plants (3 replicates, 5 plants each) underwent varied treatments: control, melatonin, salt, drought, salt + drought, salt + melatonin, drought + melatonin, and salt + drought + melatonin. Melatonin (100 µM) was alternately applied a week before stress exposure; salt stress received 100 mM NaCl every 3 days for 3 weeks, and drought stress involved 10% PEG. Young leaves were randomly sampled from each group. The results showed that melatonin treatment markedly reduces salt and drought stress damage by promoting root, shoot length, fresh and dry weight, increasing chlorophyll contents, and inhibiting excessive production of oxidative stress markers. Salt and drought stress significantly decreased the water balance, and damaged cell membrane by reducing relative water contents and increasing electrolyte leakage. However, melatonin treated rice plants showed high relative water contents and low electrolyte leakage. Under salt and drought stress conditions, exogenous application of melatonin boosted the expression level of salt and drought stress responsive genes like OsSOS, OsNHX, OsHSF and OsDREB in rice plants. Taken together, our results reveal that melatonin treatment significantly increases salt and drought tolerance of rice plants, by increasing plant biomass, suppressing ROS accumulation, elevating antioxidants defense efficiency, and up-regulating the expression of salt and drought stress responsive genes.

Drought stress tolerance in rice: a critical insight

Drought is currently a serious threat for farming especially in rice cultivation, due to its substantial water requirements throughout its lifecycle. Drought is one of the major environmental constraints disrupting the growth and yield of rice plants, affecting them at physiological, morphological, biochemical and molecular levels. Global climate change exacerbates this issue, leading to substantial economic losses. As rice is a major food crop worldwide, the demand for rice production is increasing in tandem with the expanding human population. Consequently, it has become imperative to utilize drought-prone areas for agriculture and develop drought-tolerant rice genotypes. In addition to conventional breeding methods, the application of multi-omics approaches proves most effective in meeting the need to enhance drought tolerance in rice plants. Protective mechanisms, such as morphological adaptation, physiological acclimatization, cellular adjustments and antioxidant defense, play pivotal roles in helping plants overcome drought stress. Plant-microbial interactions are important for plants to overcome drought-induced adversities. Furthermore, applications of conventional approaches, omics approaches and nanotechnology are very promising for generating climate smart agriculture. Our aim in this review is to focus on drought stress tolerance in rice including drought-tolerant rice genotypes, their adaptation mechanisms, the unveiling the genes, transcription factors, microRNAs (miRNA) involved, microbial assistance and exploring approaches to mitigate drought stress in rice plants. The present review might throw some light on understanding the mechanism of drought stress tolerance in rice, including its molecular crosstalk and biochemical dynamics, for future researchers.

Drought stress tolerance in rice: advances in physiology and genetics research

Drought stress tolerance in rice: advances in physiology and genetics research

Delineating the tissue-mediated drought stress governed tuning of conserved miR408 and its targets in rice.

Engineering drought tolerance in rice needs to focus on regulators that enhance tolerance while boosting plant growth and vigor. The present study delineated the concealed function and tissue-mediated interplay of the miR408/target module in imparting drought stress tolerance in rice. The plant miR408 family comprises three dominant mature forms (21 nt), including a distinct monocot variant (F-7 with 5' C) and is divided into six groups. miR408 majorly cleaves genes belonging to the blue copper protein in addition to several other species-specific targets in plants. Comparative sequence analysis in 4726 rice accessions identified 22 sequence variants (SNP and InDELs) in its promoter (15) and pre-miR408 region. Haplotype analysis of the sequence variants indicated eight haplotypes (three: Japonica-specific and five: Indica-specific) of the miR408 promoter. In drought-tolerant Nagina 22, miR408 follows flag leaf preferential expression. Under drought conditions, its levels are upregulated in flag leaf and roots which seems to be regulated by a differential fraction of methylated cytosines (mCs) in the precursor region. The active pool of miR408 regulated targets under control and drought conditions is impacted by the tissue type. Comparative expression analysis of the miR408/target module under different sets of conditions features 83 targets exhibiting antagonistic expression in rice, out of which 12 genes, including four PLANTACYANINS (OsUCL6, 7, 9 and 30), PIRIN, OsLPR1, OsCHUP1, OsDOF12, OsBGLU1, glycine-rich cell wall gene, OsDUT, and OsERF7, are among the high confidence targets. Further, overexpression of MIR408 in drought-sensitive rice cultivar (PB1) leads to the massive enhancement of vegetative growth in rice with improved ETR and Y(II) and enhanced dehydration stress tolerance. The above results suggest that miR408 is likely to act as a positive regulator of growth and vigor, as well as dehydration stress, making it a potential candidate for engineering drought tolerance in rice.

Genome-wide discovery of genetic variations between rice cultivars with contrasting drought stress response and their potential functional relevance.

Drought stress is a serious threat to rice productivity. Investigating genetic variations between drought-tolerant (DT) and drought-sensitive (DS) rice cultivars may decipher the candidate genes/regulatory regions involved in drought stress tolerance/response. In this study, whole-genome resequencing data of four DS and five DT rice cultivars were analyzed. We identified a total of approximately 4.8 million single nucleotide polymorphisms (SNPs) and 0.54 million insertions/deletions (InDels). The genetic variations (162,638 SNPs and 17,217 InDels) differentiating DS and DT rice cultivars were found to be unevenly distributed throughout the rice genome; however, they were more frequent near the transcription start and stop sites than in the genic regions. The cis-regulatory motifs representing the binding sites of stress-related transcription factors (MYB, HB, bZIP, ERF, ARR, and AREB) harboring the SNPs/InDels in the promoter regions of a few differentially expressed genes (DEGs) were identified. Importantly, many of these DEGs were located within the drought-associated quantitative trait loci. Overall, this study provides a valuable large-scale genotyping resource and facilitates the discovery of candidate genes associated with drought stress tolerance in rice.

Phenotyping for the Seedling Stage of the Drought Stress Tolerance in Rice (Oryza sativa L.)

The ever-increasing demand for rice raises the need to increase productivity by developing drought-tolerant rice varieties. Drought tolerance is a complex polygenic trait that largely depends upon plant developmental stages and showed genotype-specific variability. The experiment was conducted using drought tolerant (Binadhan-19, BRRI dhan83) and drought susceptible (BRRI dhan26, BRRI dhan48) rice genotypes at the glasshouse of Bangladesh Institute of Nuclear Agriculture (BINA), Mymensingh to characterize the seedling stage drought tolerance as well as disclose the variability of the genotypes for morphological and biochemical traits. A completely randomized design (CRD) with three replications and treatments (control and drought stress imposed by 20% PEG) was used for the experiment. Data on shoot length, root length, fresh root weight, fresh shoot weight, dry root weight, dry shoot weight, chlorophyll content (SPAD value), MDA, and H2O2 were recorded and analyzed through appropriate breeding tools. Significant variation (p<0.01) was observed for genotype, treatment, and genotype (G) × treatment (T) interactions viz., shoot length, root length, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, chlorophyll, H2O2, and MDA. Drought stress leads to a significant decrease in root and shoots growth whereas the level of H2O2 and MDA increased significantly. A greater decrease in root and shoot growth was observed in susceptible genotypes (BRRI dhan28, BRRI dhan48) compared to tolerant genotypes (BRRI dhan71, Binadhan-19). In contrast, a limited increase in H2O2 and MDA was recorded in tolerant genotypes compared to susceptible genotypes. H2O2 showed a significant positive correlation with root and shoot characteristics under control conditions, whereas H2O2 showed a significant negative correlation with chlorophyll content under drought conditions. MDA showed a significant negative correlation with most of the studied traits under well-watered conditions. Considering all of the traits at the seedling stage, the genotype Binadhan-19 is considered a drought-tolerant genotype both under well-watered and drought conditions, and this genotype was selected for further study under direct field conditions as well as for genetic improvement against drought stress.

Complete genome sequence analysis of a plant growth-promoting phylloplane Bacillus altitudinis FD48 offers mechanistic insights into priming drought stress tolerance in rice

Bacillus altitudinis FD48 is a multifunctional plant growth-promoting bacterium isolated from the phylloplane of rice and survives at ‐−10 bars of osmotic potential (‐−1.0 MPa). It also serves as an ideal PGPM against drought stress by triggering antioxidant defense mechanisms in rice. To further unravel the genetic determinants of osmotic stress tolerance and plant growth-promoting traits, the whole genome sequence of FD48 was compared with its related strains. The whole genome analysis revealed a single chromosome with a total length of 3,752,533 bp (3.7 Mb) and an average G + C ratio of 41.19%. A total of 4029 genes were predicted, of which 3964 (98.4%) were protein-encoding genes (PEGs) and 65 (1.6%) were non-protein-coding genes. The interaction of FD48 with the host plants is associated with many chemotactic and motility-related genes. The ability of FD48 to colonize plants and maintain plant growth under adverse environmental conditions was evidenced by the presence of genes for plant nutrient acquisition, phytohormone synthesis, trehalose, choline, and glycine betaine biosynthesis, microbial volatile organic compounds (acetoin synthesis), heat and cold shock chaperones, translation elongation factor TU (Ef-Tu), siderophore production, DEAD/DEAH boxes, and non- ribosomal peptide synthase clusters (bacilysin, fengycin, and bacitracin). This study sheds light on the drought stress-resilient mechanism, metabolic pathways and potential activity, and plant growth-promoting traits of B. altitudinis FD48 at the genetic level.

Stress-induced F-Box protein-coding gene OsFBX257 modulates drought stress adaptations and ABA responses in rice.

F-box (FB) proteins that form part of SKP1-CUL1-F-box (SCF) type of E3 ubiquitin ligases are important components of plant growth and development. Herewe characterized OsFBX257, a rice FBprotein-coding gene that is differentially expressed under drought conditions and other abiotic stresses. Population genomics analysis suggest that OsFBX257 shows high allelic diversity in aus accessions and has been under positive selection in some japonica, aromatic and indica cultivars. Interestingly, allelic variation at OsFBX257 in aus cultivar Nagina22 is associated with an alternatively spliced transcript. Conserved amongland plants, OsFBX257 is a component of the SCF complex, can form homomers and interact molecularly with the 14-3-3 rice proteins GF14b and GF14c. OsFBX257 is co-expressed in a network involving protein kinases and phosphatases. We show that OsFBX257 can bind the kinases OsCDPK1 and OsSAPK2, and that its phosphorylation can be reversed by phosphatase OsPP2C08. OsFBX257 expression level modulates root architecture and drought stress tolerance in rice. OsFBX257 knockdown (OsFBX257KD ) lines show reduced total root length and depth, crown root number, panicle size and survival under stress. In contrast, its overexpression (OsFBX257OE ) increases root depth, leaf and grain length, number of panicles, and grain yield in rice. OsFBX257 is a promising breeding target for alleviating drought stress-induced damage in rice.

Overexpression of ONAC054 Improves Drought Stress Tolerance and Grain Yield in Rice

Drought stress negatively affects plant growth and development, thus reducing plant productivity. Therefore, understanding the molecular mechanisms underlying drought stress responses is essential for crop improvement. The plant-specific NAM/ATAF1,2/CUC2 (NAC) transcription factors play important roles in the drought stress response. Here, we show that rice (Oryza sativa) ONAC054, a membrane-bound NAC transcription factor, is involved in the drought stress response. We found that onac054 mutants were sensitive, whereas ONAC054-overexpressing (ONAC054-OX) plants were tolerant to drought stress. Under drought stress conditions, several genes associated with abscisic acid (ABA) synthesis and signaling were downregulated in onac054 mutants but upregulated in ONAC054-OX plants. Among these genes, the TRANSCRIPTION FACTOR RESPONSIBLE FOR ABA REGULATION 1 (TRAB1), which encodes an ABA-inducible bZIP transcription factor, was directly activated by ONAC054. On the other hand, the expression of ONAC054 was directly activated by several ABA-responsive elements (ABRE)-binding factors (ABFs) in an ABA-dependent manner, indicating that ONAC054 acts as an enhancer of ABA-induced drought stress tolerance. Additionally, the overexpression of ONAC054 in rice greatly improved grain yield under drought stress conditions, indicating that the overexpression of ONAC054 could facilitate the improvement of drought stress tolerance in rice and other crops.

Overexpression of Asr6, abscisic acid stress-ripening protein, enhances drought tolerance and modulates gene expression in rice (Oryza sativa L.)

Rice ( Oryza sativa L.), being a paddy crop, is particularly susceptible to drought, reducing its yield drastically. Abscisic acid stress-ripening proteins (Asr) are a family of plant-specific ABA-induced low molecular weight hydrophilic proteins encoded by the stress-regulated gene. This work substantiates the biological role of rice Asr6 against drought stress by its overexpression in rice. The Asr6 overexpressing (OE) lines showed better overall growth than wild-type (WT) plants reflected by their longer shoot length with higher biomass and enhanced density of the lateral roots. The decreased level of MDA and electrolyte leakage, higher proline content, less ROS accumulation, and enhanced antioxidant enzyme activities (SOD, APX, and CAT) were observed in OE lines as compared to WT plants during drought stress. The OE lines showed better recovery than WT plants after drought stress at the reproductive stage, in the terms of the increased number of panicles and total grain yields. The transcriptome analysis revealed that Asr6 regulates the expression of a wide spectrum of genes related to hormone metabolism, stress (abiotic and biotic), transcription factors, antioxidant activity, photosynthesis, signalling, transport and secondary metabolites. Interestingly, the genes related to jasmonic acid biosynthesis (up-regulation of LOX and AOS) and signalling (up-regulation of COI1 and down-regulation of JAZ proteins) were differentially expressed in OE lines, which were further validated by qRT-PCR analysis. Our findings demonstrate, Asr6 to be a positive regulator commonly involved in tolerance to drought stress and may regulate a novel JA-dependent signalling pathway in rice for drought tolerance. • Overexpression of Asr6 can improve drought stress tolerance in rice. • Asr6 promotes lateral root growth leading to higher root biomass as compared to wild type plants under drought condition. • Asr6 transgenic rice maintains redox homeostasis on exposure to drought. • Asr6 alters the expression of jasmonic acid biosynthesis and signalling pathway genes.

The Examination of the Role of Rice Lysophosphatidic Acid Acyltransferase 2 in Response to Salt and Drought Stresses.

Phosphatidic acid (PA) is an important signal molecule in various biological processes including osmotic stress. Lysophosphatidic acid acyltransferase (LPAT) acylates the sn-2 position of the glycerol backbone of lysophosphatidic acid (LPA) to produce PA. The role of LPAT2 and its PA in osmotic stress response remains elusive in plants. Here we showed that LPAT2-derived PA is important for salt and drought stress tolerance in rice. Rice LPAT2 was localized to the endoplasmic reticulum (ER) to catalyze the PA synthesis. The LPAT2 transcript was induced by osmotic stress such as high salinity and water deficit. To reveal its role in osmotic stress response, an LPAT2 knockdown mutant, designated lpat2, was isolated from rice, which contained a reduced PA level relative to wild type (WT) plants under salt stress and water deficit. The lpat2 mutant was more susceptible to osmotic stress and less sensitive to abscisic acid (ABA) than that of WT, which was recovered by either PA supplementation or genetic LPAT2 complementation. Moreover, suppressed LPAT2 also led to a large number of differentially expressed genes (DEGs) involved in diverse processes, particularly, in ABA response, kinase signaling, and ion homeostasis in response to salt stress. Together, LPAT2-produced PA plays a positive role in osmotic tolerance through mediating ABA response, which leads to transcriptional alteration of genes related to ABA response, protein kinase signaling, and ion homeostasis.

Straw Incorporation in Contaminated Soil Enhances Drought Tolerance but Simultaneously Increases the Accumulation of Heavy Metals in Rice

Heavy metals (HMs) and drought stress are worldwide issues of concern because of their adverse effects on the growth and productivity of rice. Straw burning causes air pollution via greenhouse gas (GHG) emissions and it requires sustainable management. The introduction of HMs into the food chain poses a major health risk to humans. In this regard, straw incorporation into the soil could reduce air pollution and drought stress. However, its simultaneous impact on HMs’ uptake and drought stress tolerance in crops is unknown. Therefore, the present study aimed to investigate the impact of rice straw incorporation in soil on HMs (Cd, Cu, Pb, and Fe) availability, accumulation, and drought stress tolerance in rice (Oryza sativa L.) grown in pots under glasshouse conditions. The soil samples were collected from a non-contaminated agricultural field (control) and the contaminated field, irrigated with industrial effluent and treated with straw. Straw (1% w/w) was mixed in soils and control plants without straw application were grown under both contaminated and normal soil conditions. The results showed that straw incorporation in soils significantly enhanced the accumulation of HMs in rice grain and other vegetative parts of rice as compared to control. Moreover, straw application harmed chlorophyll and carotenoids. Straw application significantly increased proline in leaves (274.0 µg mL−1) as compared to the control (166.8 µg mL−1). Relative water contents were higher in straw-treated plants, thereby increasing drought stress tolerance. Straw application increased the accumulation of HMs and consequently reduced the biomass of the plant. In conclusion, straw incorporation enhanced drought stress tolerance but simultaneously elevated the accumulation of HMs under contaminated soil in Oryza sativa L.

Poaceae Orthologs of Rice OsSGL, DUF1645 Domain-Containing Genes, Positively Regulate Drought Tolerance, Grain Length and Weight in Rice

Grain yield is a polygenic trait that can be influenced by environmental factors and genetic compositions at all plant growth stages. Currently, the molecular mechanisms behind the coordination of the interaction between grain yield-related traits remain unknown. In this study, we characterized the function of four STRESS_tolerance and GRAIN_LENGTH (OsSGL) Poaceae ortholog genes that are transcribed into DUF1645 domain-containing proteins in relation to the grain length, grain weight, and drought stress-tolerance of rice. The transgenic plants with overexpressing or heterologous high levels of Poaceae OsSGL ortholog genes exhibited longer grain size than the wild type plants. Larger cells were seen in panicles of the four transgenic lines with paraffin sectioning and scanning electron microscopy analyses. In addition, four Poaceae OsSGL ortholog genes positively affected the drought tolerance of rice. Four transgenic plants displayed higher resistance to drought stress at the seedling and vegetative stages. RNA-sequencing and qRT-PCR results indicated that over- or heterologous-expression of four Poaceae OsSGL ortholog genes also affected the transcriptome of rice plants. These genes may play a role in auxin and cytokinin biosynthesis and their transduction pathways. Taken together, these results suggested that the four OsSGL orthologs have a conserved function in the regulation of stress-tolerance and cell growth by modulating hormonal biosynthesis and signaling.

Recent Advances in Different Omics Mechanism for Drought Stress Tolerance in Rice

Recent Advances in Different Omics Mechanism for Drought Stress Tolerance in Rice

Rice Carbohydrate-Binding Malectin-Like Protein, OsCBM1, Contributes to Drought-Stress Tolerance by Participating in NADPH Oxidase-Mediated ROS Production

Carbohydrate-binding malectin/malectin-like domain-containing proteins (CBMs) are a recently identified protein subfamily of lectins that participates various functional bioprocesses in the animal, bacterial, and plant kingdoms. However, little is known the roles of CBMs in rice development and stress response. In this study, OsCBM1, which encodes a protein containing only one malectin-like domain, was cloned and characterized. OsCBM1 is localized in both the endoplasmic reticulum and plasma membrane. Its transcripts are dominantly expressed in leaves and could be significantly stimulated by a number of phytohormone applications and abiotic stress treatments. Overexpression of OsCBM1 increased drought tolerance and reactive oxygen species production in rice, whereas the knockdown of the gene decreased them. OsCBM1 physically interacts with OsRbohA, a NADPH oxidase, and the expression of OsCBM1 in osrbohA, an OsRbohA-knockout mutant, is significantly downregulated under both normal growth and drought stress conditions. Meanwhile, OsCBM1 can also physically interacts with OsRacGEF1, a specific guanine nucleotide exchange factor for the Rop/Rac GTPase OsRac1, and transient coexpression of OsCBM1 with OaRacGEF1 significantly enhanced ROS production. Further transcriptome analysis showed that multiple signaling regulatory mechanisms are involved in the OsCBM1-mediated processes. All these results suggest that OsCBM1 participates in NADPH oxidase-mediated ROS production by interacting with OsRbohA and OsRacGEF1, contributing to drought stress tolerance of rice. Multiple signaling pathways are likely involved in the OsCBM1-mediated stress tolerance in rice.

Gain-of-function mutagenesis through activation tagging identifies XPB2 and SEN1 helicase genes as potential targets for drought stress tolerance in rice.

XPB2 and SEN1 helicases were identified through activation tagging as potential candidate genes in rice for inducing high water-use efficiency (WUE) and maintaining sustainable yield under drought stress. As a follow-up on the high-water-use-efficiency screening and physiological analyses of the activation-tagged gain-of-function mutant lines that were developed in an indica rice variety, BPT-5204 (Moin et al. in Plant Cell Environ 39:2440-2459, 2016a, https://doi.org/10.1111/pce.12796 ), we have identified two gain-of-function mutant lines (XM3 and SM4), which evidenced the activation of two helicases, ATP-dependent DNA helicase (XPB2) and RNA helicase (SEN1), respectively. We performed the transcript profiling of XPB2 and SEN1 upon exposure to various stress conditions and found their significant upregulation, particularly in ABA and PEG treatments. Extensive morpho-physiological and biochemical analyses based on 24 metrics were performed under dehydration stress (PEG) and phytohormone (ABA) treatments for the wild-type and the two mutant lines. Principal component analysis (PCA) performed on the dataset captured 72.73% of the cumulative variance using the parameters influencing the first two principal components. The tagged mutants exhibited reduced leaf wilting, improved revival efficiency, constant amylose:amylopectin ratio, high chlorophyll and proline contents, profuse tillering, high quantum efficiency and yield-related traits with respect to their controls. These observations were further validated under greenhouse conditions by the periodic withdrawal of water atthe pot level. Germination of the seeds of these mutant lines indicated their insensitivity to high ABA concentration. The associated upregulation of stress-specific genes further suggests that their drought tolerance might be because of the coordinated expression of several stress-responsive genes in these two mutants. Altogether, our results provided a firm basis for SEN1 and XPB2 as potential candidates for manipulation of drought tolerance and improving rice performance and yield under limited water conditions.

Identification and characterization of genes responsive to drought and heat stress in rice (Oryza sativa L.)

Rice is considered as a major source of food for most people worldwide. Global rice production is under threat as a result of adverse effects of heat and drought stress. It is therefore necessary to safeguard its sustainable production. This study was carried out to characterize differentially expressed genes (DEGs) under both drought and heat stresses in rice. 1001 DEGs were determined to show up-regulation under heat and drought stresses, while 1690 DEGs were commonly down-regulated. Functional classification analysis generated 22 and 37 related gene groups from the commonly up-regulated and down-regulated genes respectively. Functional characterization revealed 38.1% and 45.2% DEGs annotating for Biological Process, 53.2% and 59.2% DEGs were for Cellular Components and 54.8% and 52.4% DEGs were for Molecular Function in the up and down commonly regulated DEGs respectively. KEGG analysis demonstrated that most of the up-regulated DEGs were particularly enriched in metabolic pathways and in the biosynthesis of secondary metabolites, while the down regulated genes were mostly enriched in pathways involving ribosomes, and in purine and pyrimidine metabolisms. These results could be helpful in further analysis and understanding of heat and drought stress tolerance in rice.

Introduction pages

Notulae Botanicae Horti Agrobotanici Cluj-Napoca (NBHA): The papers published in Issue 4, Volume 48, 2020 represent new exciting researches in different topics of life science, respectively in plant science, horticulture, agronomy and crop science. Among the interesting articles we invite you to find news about: Exploring Artemisia annua L., artemisinin and its derivatives, from traditional Chinese wonder medicinal science; A critical review on the improvement of drought stress tolerance in rice (Oryza sativa L.); Plantation forestry in Malaysia: an evaluation of its successes and failures since the 1970; Transcriptome analysis to identify genes involved in lignan, sesquiterpenoid and triterpenoid biosynthesis in medicinal plant Kadsura heteroclite; Molecular cloning and characterization of a lipoxygenase gene (CsLOX1) from cucumber; Genetic relationship of mungbean and blackgram genotypes based on agronomic and photosynthetic performance and SRAP markers; Callogenesis optimization of some globe artichoke [Cynara cardunculus var. scolymus (L.) Fiori] cultivars based on in vivo and in vitro leaf explants; Chemical composition and antimicrobial and antioxidant activities of Tunisian, France and Austrian Laurus nobilis (Lauraceae) essential oils etc. The new Impact Factor communicated by ISI Clarivate, June 29, 2020, is IF 2019 = 1.168 (position 149 of 234 journals, Q3 in Plant Sciences). New metrics in Scopus – Elsevier (June 22, 2020): CiteScore 1.40 (#43/84 in Horticulture); SJR 0.35 - Q2, #41/90 in Horticulture (SJR Scimago Journal).

A critical review on the improvement of drought stress tolerance in rice (Oryza sativa L.)

Abiotic stresses are the primary threat to crop production across the globe. Drought stress is primary abiotic stress which is considerably limiting the global rice production and putting the food security at higher risks. Drought tolerance (DT) is a multigene trait which is influenced by various stages of development in rice plant. Tolerance as well as susceptibility of rice to drought stress is carried out by different drought-response genes and other components of stress. Plant researchers have used various methods such as, genetic manipulation and marker-assisted techniques for development of new rice cultivars with improved tolerance to drought stress. The aims of this review are to present recent advancements and illustrate current approaches to breed a robust drought-resistant rice genotypes by using classical breeding and advanced molecular techniques. We also shed light on all available information regarding the role of significant hormones in DT, QTL for drought-related traits, QTL for rice yield, global strategies for the improvement of DT in rice, DT genes, and selection supported by markers.