The influence of climate change on the sesame yield in North Gondar, North Ethiopia: Application Autoregressive Distributed Lag (ARDL) time series model.

Sesame is a major annual oil crop that is grown practically everywhere in tropical and subtropical Asia, as well as Africa, for its very nutritious and tasty seeds. Rising temperatures, droughts, floods, desertification, and weather all have a significant impact on agricultural production, particularly in developing countries like Ethiopia. Therefore, the main objective of this study is to examine the influence of climate change on the sesame yield in North Gondar, North Ethiopia, by using the autoregressive distributed Lag (ARDL) time series model. This study employed climate data from the Bahirdar Agrometeorological Center and secondary data on sesame production from the Ethiopian Statistical Service, spanning 36 years, from 1987 to 2023. Autoregressive Distributed LAG (ARDL) includes diagnostic tests for both short- and long-term autoregressive models. The results for the long-run and short-run elastic coefficients show a significant positive association between temperatures and sesame yield. Sesame yield and rainfall have a significant negative long-run and short-run relationship in North Gondar, North Ethiopia. ARDL results confirm that temperature and rainfall have significant effects on sesame productivity. Temperature had a considerable favorable effect on sesamen production, but rainfall had a negative effect in North Gondar, Ethiopia. Based on the evidence acquired from our study, we made several policy recommendations and suggestions to government officials, policymakers, new technologies, researchers, policy development planners, and other stakeholders in order to develop or implement new technology to halt its production and direct adaptation measures in light of the certainty of global warming and the characteristics of climate-dependent agricultural production.

Determination of Main Bitter Compounds in Soaked and Germinated Sesame Pastes.

The flavor and taste of the foods play an important or even a decisive role in the acceptance and preference of the consumers. It was found that the sesame paste prepared with the germinated sesame seeds was bitter in our previous experiment. In the study, the volatile and non-volatile bitter-taste components of the sesame paste samples were comprehensively analyzed. 2-methylbutanal, hexanal, acetic acid, and butyric acid were the predominant volatile compounds in the soaked and germinated sesame pastes. Oxalate was significantly reduced by the germination (p < 0.05). The contents of sesaminoltriglucoside in sesame pastes ranged from 129.04 to 217.57 µg/g. Both total and individual free amino acid contents increased with the prolongation of the germinating time. The bitter-taste amino acid Arg had the highest score of Taste Activity Value for the bitterest sample made from the seeds germinated for 36 hours. The bitter-tasting Arg was first reported to impart a bitter taste to the germinated sesame paste.

Transcriptomic profiling of sesame during waterlogging and recovery.

Sesame is naturally adapted to arid environments but highly susceptible to waterlogging stress. A few hours of waterlogging (lasting over 36 h) are detrimental to the crop growth, yield and survival. To better understand the molecular mechanisms underlying sesame responses to waterlogging and recovery, it is essential to design a high-resolution time-series experiment. In this study, we reported the RNA-seq profiling of two contrasting genotypes under waterlogging and recovery. The plants were grown in pots and subjected to waterlogging treatment at the flowering stage for 36 h and subsequently, 12 h drainage. Root samples were collected in triplicate at 22 time points under waterlogging/drainage treatments and at 10 time points in the control condition. This represents a total of 195 biological samples and the RNA-seq yielded over eight billion reads. Basic data analyses demonstrated a clear separation of transcriptomes from control, waterlogging and drainage treatments. Overall, the generated high-quality and comprehensive RNA-seq resources will undoubtedly advance our understanding of waterlogging/drainage responses in a non-model sensitive crop.

Genome-wide characterization and expression analysis of the HD-Zip gene family in response to drought and salinity stresses in sesame.

BACKGROUND: The homeodomain-leucine zipper (HD-Zip) gene family is one of the plant-specific transcription factor families, involved in plant development, growth, and in the response to diverse stresses. However, comprehensive analysis of the HD-Zip genes, especially those involved in response to drought and salinity stresses is lacking in sesame (Sesamum indicum L.), an important oil crop in tropical and subtropical areas. RESULTS: In this study, 45 HD-Zip genes were identified in sesame, and denominated as SiHDZ01-SiHDZ45. Members of SiHDZ family were classified into four groups (HD-Zip I-IV) based on the phylogenetic relationship of Arabidopsis HD-Zip proteins, which was further supported by the analysis of their conserved motifs and gene structures. Expression analyses of SiHDZ genes based on transcriptome data showed that the expression patterns of these genes were varied in different tissues. Additionally, we showed that at least 75% of the SiHDZ genes were differentially expressed in responses to drought and salinity treatments, and highlighted the important role of HD-Zip I and II genes in stress responses in sesame. CONCLUSIONS: This study provides important information for functional characterization of stress-responsive HD-Zip genes and may contribute to the better understanding of the molecular basis of stress tolerance in sesame.

Transcriptomic and metabolomic profiling of drought-tolerant and susceptible sesame genotypes in response to drought stress.

BACKGROUND: Sesame is an important oil crop due to its high oil, antioxidant, and protein content. Drought stress is a major abiotic stress that affects sesame production as well as the quality of sesame seed. To reveal the adaptive mechanism of sesame in response to water deficient conditions, transcriptomic and metabolomics were applied in drought-tolerant (DT) and drought-susceptible (DS) sesame genotypes. RESULTS: Transcriptomic analysis reveals a set of core drought-responsive genes (684 up-regulated and 1346 down-regulated) in sesame that was robustly differently expressed in both genotypes. Most enriched drought-responsive genes are mainly involved in protein processing in endoplasmic reticulum, plant hormone signal transduction photosynthesis, lipid metabolism, and amino acid metabolism. Drought-susceptible genotype was more disturbed by drought stress at both transcriptional and metabolic levels, since more drought-responsive genes/metabolites were identified in DS. Drought-responsive genes associated with stress response, amino acid metabolism, and reactive oxygen species scavenging were more enriched or activated in DT. According to the partial least-squares discriminate analysis, the most important metabolites which were accumulated under drought stress in both genotypes includes ABA, amino acids, and organic acids. Especially, higher levels of ABA, proline, arginine, lysine, aromatic and branched chain amino acids, GABA, saccharopine, 2-aminoadipate, and allantoin were found in DT under stress condition. Combination of transcriptomic and metabolomic analysis highlights the important role of amino acid metabolism (especially saccharopine pathway) and ABA metabolism and signaling pathway for drought tolerance in sesame. CONCLUSION: The results of the present study provide valuable information for better understanding the molecular mechanism underlying drought tolerance of sesame, and also provide useful clues for the genetic improvement of drought tolerance in sesame.

Nectar robbing in bellflower (Sesamum radiatum) benefited pollinators but unaffected maternal function of plant reproduction.

Nectar robbing - foraging nectar illegitimately - has negative, neutral, or positive effects on maternal function of plant reproduction and/or on pollinators. It has been suggested that nectar robbing has a non-negative effect on maternal function of plant reproduction in autogamous and mixed breeding plants; however this hypothesis requires deeper understanding with more studies. We investigated the impact of natural nectar robbing on maternal function of plant reproduction and visitation characteristics of pollinators in Sesamum radiatum, an autogamous plant. Pollinators were observed on unrobbed open flowers and robbed open flowers. In robbed flowers, pollinators' visit type and foraging time were examined. The seed sets of these flower types were examined. Xylocopa latipes was both a primary robber and a legitimate pollinator, X. bryorum was an exclusive primary robber, and Megachile disjuncta was a cosmopolitan pollinator. In robbed flowers, most of the pollinators foraged mostly as secondary nectar robbers. The foraging time shortened considerably when pollinators robbed nectar - a positive effect on pollinators' foraging efficiency. Robbing did not negatively affect seed set - a neutral effect on the plant's reproduction. Our study agrees that nectar robbing might have a non-negative effect on reproduction in autogamous and mixed breeding plants.

The genetic basis of drought tolerance in the high oil crop Sesamum indicum.

Unlike most of the important food crops, sesame can survive drought but severe and repeated drought episodes, especially occurring during the reproductive stage, significantly curtail the productivity of this high oil crop. Genome-wide association study was conducted for traits related to drought tolerance using 400 diverse sesame accessions, including landraces and modern cultivars. Ten stable QTLs explaining more than 40% of the phenotypic variation and located on four linkage groups were significantly associated with drought tolerance related traits. Accessions from the tropical area harboured higher numbers of drought tolerance alleles at the peak loci and were found to be more tolerant than those from the northern area, indicating a long-term genetic adaptation to drought-prone environments. We found that sesame has already fixed important alleles conferring survival to drought which may explain its relative high drought tolerance. However, most of the alleles crucial for productivity and yield maintenance under drought conditions are far from been fixed. This study also revealed that pyramiding the favourable alleles observed at the peak loci is of high potential for enhancing drought tolerance in sesame. In addition, our results highlighted two important pleiotropic QTLs harbouring known and unreported drought tolerance genes such as SiABI4, SiTTM3, SiGOLS1, SiNIMIN1 and SiSAM. By integrating candidate gene association study, gene expression and transgenic experiments, we demonstrated that SiSAM confers drought tolerance by modulating polyamine levels and ROS homeostasis, and a missense mutation in the coding region partly contributes to the natural variation of drought tolerance in sesame.

Photoperiod response-related gene SiCOL1 contributes to flowering in sesame.

BACKGROUND: Sesame is a major oilseed crop which is widely cultivated all around the world. Flowering, the timing of transition from vegetative to reproductive growth, is one of the most important events in the life cycle of sesame. Sesame is a typical short-day (SD) plant and its flowering is largely affected by photoperiod. However, the flowering mechanism in sesame at the molecular level is still not very clear. Previous studies showed that the CONSTANS (CO) gene is the crucial photoperiod response gene which plays a center role in duration of the plant vegetative growth. RESULTS: In this study, the CO-like (COL) genes were identified and characterized in the sesame genome. Two homologs of the CO gene in the SiCOLs, SiCOL1 and SiCOL2, were recognized and comprehensively analyzed. However, sequence analysis showed that SiCOL2 lacked one of the B-box motifs. In addition, the flowering time of the transgenic Arabidopsis lines with overexpressed SiCOL2 were longer than that of SiCOL1, indicating that SiCOL1 was more likely to be the potential functional homologue of CO in sesame. Expression analysis revealed that SiCOL1 had high expressed levels before flowering in leaves and exhibited diurnal rhythmic expression in both SD and long-day (LD) conditions. In total, 16 haplotypes of SiCOL1 were discovered in the sesame collections from Asia. However, the mutated haplotypes did not express under both SD and LD conditions and was regarded as a nonfunctional allele. Notably, the sesame landraces from high-latitude regions harboring nonfunctional alleles of SiCOL1 flowered much earlier than landraces from low-latitude regions under LD condition, and adapted to the northernmost regions of sesame cultivation. The result indicated that sesame landraces from high-latitude regions might have undergone artificial selection to adapt to the LD environment. CONCLUSIONS: Our results suggested that SiCOL1 might contribute to regulation of flowering in sesame and natural variations in SiCOL1 were probably related to the expansion of sesame cultivation to high-latitude regions. The results could be used in sesame breeding and in broadening adaptation of sesame varieties to new regions.

Genome-wide identification and expression analyses of genes involved in raffinose accumulation in sesame.

Sesame (Sesamum indicum L.) is an important oilseed crop. However, multiple abiotic stresses severely affect sesame growth and production. Raffinose family oligosaccharides (RFOs), such as raffinose and stachyose, play an important role in desiccation tolerance of plants and developing seeds. In the present study, three types of key enzymes, galactinol synthase (GolS), raffinose synthase (RafS) and stachyose synthase (StaS), responsible for the biosynthesis of RFOs were identified at the genome-wide scale in sesame. A total of 7 SiGolS and 15 SiRS genes were identified in the sesame genome. Transcriptome analyses showed that SiGolS and SiRS genes exhibited distinct expression profiles in different tissues and seed developmental stages. Comparative expression analyses under various abiotic stresses indicated that most of SiGolS and SiRS genes were significantly regulated by drought, osmotic, salt, and waterlogging stresses, but slightly affected by cold stress. The up-regulation of several SiGolS and SiRS genes by multiple abiotic stresses suggested their active implication in sesame abiotic stress responses. Taken together, these results shed light on the RFOs-mediated abiotic stress resistance in sesame and provide a useful framework for improving abiotic stress resistance of sesame through genetic engineering.

Genome-wide analysis of WRKY gene family in the sesame genome and identification of the WRKY genes involved in responses to abiotic stresses.

BACKGROUND: Sesame (Sesamum indicum L.) is one of the world's most important oil crops. However, it is susceptible to abiotic stresses in general, and to waterlogging and drought stresses in particular. The molecular mechanisms of abiotic stress tolerance in sesame have not yet been elucidated. The WRKY domain transcription factors play significant roles in plant growth, development, and responses to stresses. However, little is known about the number, location, structure, molecular phylogenetics, and expression of the WRKY genes in sesame. RESULTS: We performed a comprehensive study of the WRKY gene family in sesame and identified 71 SiWRKYs. In total, 65 of these genes were mapped to 15 linkage groups within the sesame genome. A phylogenetic analysis was performed using a related species (Arabidopsis thaliana) to investigate the evolution of the sesame WRKY genes. Tissue expression profiles of the WRKY genes demonstrated that six SiWRKY genes were highly expressed in all organs, suggesting that these genes may be important for plant growth and organ development in sesame. Analysis of the SiWRKY gene expression patterns revealed that 33 and 26 SiWRKYs respond strongly to waterlogging and drought stresses, respectively. Changes in the expression of 12 SiWRKY genes were observed at different times after the waterlogging and drought treatments had begun, demonstrating that sesame gene expression patterns vary in response to abiotic stresses. CONCLUSIONS: In this study, we analyzed the WRKY family of transcription factors encoded by the sesame genome. Insight was gained into the classification, evolution, and function of the SiWRKY genes, revealing their putative roles in a variety of tissues. Responses to abiotic stresses in different sesame cultivars were also investigated. The results of our study provide a better understanding of the structures and functions of sesame WRKY genes and suggest that manipulating these WRKYs could enhance resistance to waterlogging and drought.

Sesame (Sesamum indicum L.).

Sesame (Sesamum indicum L.) is an important oilseed crop grown in India, China, Korea, Russia, Turkey, Mexico, South America, and several countries of Africa. Sesame seeds are rich in oil, proteins, unsaturated fatty acids, vitamins, minerals, and folic acid. Nearly 70% of the world's sesame is processed into oil and meal, while the remainder is channeled to food and confectionery industries. Production of sesame is limited by several fungal diseases, water logging, salinity, and shattering of seed capsules during harvest. Introgression of useful genes from wild species into cultigens by conventional breeding has not been successful due to postfertilization barriers. The only alternative for the improvement of S. indicum is to transfer genes from other sources through genetic transformation techniques. Here, we describe a simple, fast, and reproducible method for the Agrobacterium-mediated genetic transformation of S. indicum which may be employed for the transfer of desirable traits into this economically important oilseed crop.

IAA-producing Penicillium sp. NICS01 triggers plant growth and suppresses Fusarium sp.-induced oxidative stress in sesame (Sesamum indicum L.).

Application of rhizospheric fungi is an effective and environmentally friendly method of improving plant growth and controlling many plant diseases. The current study was aimed to identify phytohormone-producing fungi from soil, to understand their roles in sesame plant growth, and to control Fusarium disease. Three predominant fungi (PNF1, PNF2, and PNF3) isolated from the rhizospheric soil of peanut plants were screened for their growth-promoting efficiency on sesame seedlings. Among these isolates, PNF2 significantly increased the shoot length and fresh weight of seedlings compared with controls. Analysis of the fungal culture filtrate showed a higher concentration of indole acetic acid in PNF2 than in the other isolates. PNF2 was identified as Penicillium sp. on the basis of phylogenetic analysis of ITS sequence similarity. The in vitro biocontrol activity of Penicillium sp. against Fusarium sp. was exhibited by a 49% inhibition of mycelial growth in a dual culture bioassay and by hyphal injuries as observed by scanning electron microscopy. In addition, greenhouse experiments revealed that Fusarium inhibited growth in sesame plants by damaging lipid membranes and reducing protein content. Co-cultivation with Penicillium sp. mitigated Fusarium-induced oxidative stress in sesame plants by limiting membrane lipid peroxidation, and by increasing the protein concentration, levels of antioxidants such as total polyphenols, and peroxidase and polyphenoloxidase activities. Thus, our findings suggest that Penicillium sp. is a potent plant growthpromoting fungus that has the ability to ameliorate damage caused by Fusarium infection in sesame cultivation.

Morpho-anatomical and physiological responses to waterlogging of sesame (Sesamum indicum L.).

Waterlogging threatens severely to the sesame production in China, India and Burma, which are the top three sesame producers of the world. It was of great importance to explore the dynamics and mechanisms of action of anaerobic proteins and antioxidant enzymes together with the morph-anatomic adaptions in waterlogged sesame. The sesame accessions ZZM2541 and Ezhi-2 respond to waterlogging in considerably different performance. The stress induced wilting and leaf chlorosis in both accessions, but symptom occurred earlier in the susceptive Ezhi-2. In the more tolerant ZZM2541, adventitious roots formed above the flooding level, and plentiful of aerenchyma developed in the root and stem. However, it was discovered no apparent intercellular spaces existing in the spongy mesophyll in leaves of both accessions. The activities of ADH, PDC and LDH increased in roots of both accessions after suffering of the stress. The increase of ADH and PDC activity was more pronounced in ZZM2541, while a significantly higher LDH activity appeared in Ezhi-2. All the activities of SOD, APX and CAT were higher in the leaves of ZZM2541 than in Ezhi-2, and the leaves of Ezhi-2 showed a higher content of MDA throughout the duration of waterlogging. It was suggested that the tolerance to waterlogging of ZZM2541 appears to depend on a combination of metabolic and morpho-anatomical adaptions.

Penicillium sp. mitigates Fusarium-induced biotic stress in sesame plants.

Fusarium-infected sesame plants have significantly higher contents of amino acids (Asp, Thr, Ser, Asn, Glu, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, Lys, His, Try, Arg, and Pro), compared with their respective levels in the healthy control. These higher levels of amino acids induced by Fusarium infection were decreased when Penicillium was co-inoculated with Fusarium. Compared with the control, Fusarium-infected plants showed higher contents of palmitic (8%), stearic (8%), oleic (7%), and linolenic acids (4%), and lower contents of oil (4%) and linoleic acid (11%). Co-inoculation with Penicillium mitigated the Fusarium-induced changes in fatty acids. The total chlorophyll content was lower in Fusarium- and Penicillium-infected plants than in the healthy control. The accumulation of carotenoids and γ-amino butyric acid in Fusarium-infected plants was slightly decreased by co-inoculation with Penicillium. Sesamin and sesamolin contents were higher in Penicillium- and Fusarium- infected plants than in the control. PURPOSE OF WORK: To clarify the mechanism of the biocontrol effect of Penicillium against Fusarium by evaluating changes in primary and secondary metabolite contents in sesame plants.

Establishment of regeneration and transformation system in Egyptian sesame (Sesamum indicum L.) cv Sohag 1.

Sesame (Sesamum indicum L.) is an important oil crop in many tropical and sub-tropical regions of the world, yet has received little attention in applying modern biotechnology in its improvement due to regeneration and transformation difficulties. Here within, we report the successful production of transgenic fertile plants of sesame (cv Sohag 1), after screening several cultivars. Agrobacterium tumefaciens- carrying the pBI121 plasmid {neomycin phosphotransferase gene (NPTII) and a ß-glucuronidase gene (GUS)} was used in all experiments. Recovery of transgenic sesame shoots was achieved using shoot induction medium (Murashige and Skoog MS basal salt mixture + Gamborg's B5 vitamins + 2.0 mg/l BA + 1.0 mg/l IAA + 5.0 mg/l AgNO3 + 30.0 g/l sucrose + 7.0 g/l agar + 200 mg/l cefotaxime and 25 mg/l kanamycin) and shoots were rooted on MS medium + B5 vitamins + 1.0 mg/l IAA + 10.0 g/l sucrose and 7.0 g/l agar. Rooted shoots were transplanted into soil and grown to maturity in greenhouse. Incorporation and expression of the GUS gene into T0 sesame plants was confirmed using polymerase chain reaction (PCR), reverse transcriptase-PCR (RT-PCR) and GUS histochemical assay. Several factors were found to be important for regeneration and transformation in sesame. The most effective were plant genotype and the addition of AgNO3 for successful recovery of sesame shoots. Co-cultivation time and optical density of the Agrobacterium were also critical for sesame transformation. This work is an attempt to open the door for further genetic improvement of sesame using important agronomic traits.

Hypersensitive response of Sesamum prostratum Retz. elicitated by Fusarium oxysporum f. sesame (Schelt) Jacz Butler.

Aim of this study was to investigate the intensity and timing of the ROS formation, lipid peroxidation and expression of antioxidant enzymes as initial responses of calli of Sesamum prostratum (SP) against Fusarium oxysporum f. sesame crude toxin metabolite of varying concentrations. 2,4 dichlorophenoxy acetic acid (2,4-D) / coconut milk combinations were found to be more efficient among different hormonal regimes (2,4 -D, 2,4-D/casein hydrosylate and 2,4-D/ coconut milk). The concentration of hydrogen peroxide and lipid peroxidation were higher (13.2 and 5.7-folds, respectively) after 6 h in the treated callus confirmed the oxidative stress. An increase in total phenolics was also detected in inoculated callus. Increased activity of antioxidative enzymes viz., NADPH oxidase and superoxide dismutase (SOD) corroborate with the high level of ROSs, such as O2*- and H2O2. The poor activity of catalase confirmed the oxidative burst in the callus leading to necrosis. Activity of peroxidase was at par with total phenolics. Similarly, phenylalanine ammonia lyase (PAL) also showed high activity revealing the active phase in the synthesis of secondary metabolites in the plant. The oxidative burst generated in the interaction between Sesamum and F. oxysporum f. sesame toxin might be the first line of defense by the host mounted against the invading necrotrophic pathogen. The results suggested that the rapid production of reactive oxygen species in the callus in response to fungal toxin had been proposed to orchestrate the establishment of different defensive barriers against the pathogens.