Enhancement of Thiamine Biosynthesis in Oil Palm Seedlings by Colonization of Endophytic Fungus Hendersonia toruloidea

Exploring the modulatory effects of brown seaweed meal and extracts on intestinal microbiota and morphology of broiler chickens challenged with heat stress

Brown seaweed (Ascophyllum nodosum) is known for its prebiotic roles and can improve animal intestinal health by enhancing the growth of beneficial microbes and inhibiting pathogenic ones. However, the gut health-modulatory roles of brown seaweed on chickens challenged with heat stress (HS) are rarely studied. The current study examined the effects of brown seaweed meal (SWM) and extract (SWE) on the ceca microbiota and small intestinal morphology of chickens challenged or unchallenged with HS. Three hundred and thirty-six 1-day-old Ross 308 broiler chicks were randomly assigned to either a thermoneutral (TN; 24 ± 1°C); or HS room (HS; 32-34°C, 8 h/d from d 21 to 27). All birds in each room were randomly allotted to 4 treatments - control (CON), CON + 1 mL/L seaweed extract (SWE) in drinking water, CON + 2 mL/L SWE in drinking water, and CON + 2% seaweed meal (SWM) in feed and raised for 28 d. On d 14 and 28, 12 and 24 birds per treatment group, respectively, were euthanized to collect the ceca content for gut microbiota analysis and small intestinal tissues for morphological examination. On d 14, 2% SWM increased (P = 0.047) the relative abundance of cecal Fecalibacterium and all brown seaweed treatments improved jejunal villus height (VH) and VH:CD compared to the CON diet. On d 28, HS significantly reduced (P < 0.05) ileal VH, VW, and VH:CD, and duodenal VH and VH:CD. Among the HS group, 2% SWM and 2 mL/L SWE significantly increased (P < 0.05) the relative abundance of Lactobacillus, Sellimonas, and Fournierella, compared to the CON diet. HS birds fed with 2% SWM had higher ileal VH and VH:CD compared to other treatments. In summary, SWM and SWE enhanced the abundance of beneficial microbes and improved small intestinal morphology among HS chickens. This implies that seaweed could potentially alleviate HS-induced intestinal impairment in chickens.

Endophytic Bacteria Induce Thiamine (Vitamin B1) Production in Oil Palm (Elaeis guineensis)

Thiamine or vitamin B1 is a micronutrient that has a crucial function in all living organisms and involved in several biochemical reactions. Concerning the capability of thiamine in inducing plant health, a study was carried out by applying bacterial endophytes (Pseudomonas aeruginosa and Burkholderia cepacia cultures) in four-month-old oil palm seedlings (Elaeis guineensis) via soil drenching technique to evaluate the effect towards thiamine. Spear leaves were sampled day 0 to 14 to analyse the expression of gene coding for the first two enzymes thiamine biosynthesis pathway, THI4 and THIC via qPCR analysis. The gene expression by qPCR showed a significant increase of up to 3-fold while high-performance liquid chromatography (HPLC) analysis for quantification of thiamine and its derivatives accumulated ~ 20-fold in total thiamine when compared to control seedlings. However, concentration of thiamine metabolites was negatively correlated with the expression of THIC and THI4 gene transcripts suggesting post-transcriptional regulation mediated by an RNA regulatory element, a thiamine pyrophosphate (TPP) riboswitch. Our findings demonstrated that the application of bacterial endophytes affected thiamine biosynthesis and enhanced overall thiamine content. This might increase the plant's resistance towards stress and would be useful in oil palm maintenance for maximum yield production.

Fabrication and performance analysis of keratin based-graphene oxide nanocomposite to remove dye from tannery wastewater

In recent years, nanomaterials and composites have become increasingly significant as adsorbents in the removal of dyes and phenolic contaminants from wastewater. This study presents the development and application of a keratin-based graphene oxide nanocomposite, distinguished by its enhanced biocompatibility, cost-effectiveness, and strong affinity for organic compounds, making it highly effective in reducing dyes within tannery effluent. The nanocomposite was prepared via solution casting method, with dispersibility, chemical bonding, and morphology analyzed by UV-Vis spectroscopy, FTIR, and SEM, respectively. Furthermore, investigations of the influence of several factors, such as contact time, pH, and adsorbent dosage on the optimization of the process were conducted. An observation indicated a reduction of approximately 98.8 % in dye content within 20 min, achieved through the use of an adsorbent dosage of 1.5 g/L, with the solution pH maintained at 5. Subsequently, adsorption kinetics and isotherm modelling were analyzed. The results revealed that the adsorption process follows the pseudo-second-order kinetics and Freundlich isotherm models. Hence, the adsorption could be explained as chemisorption with a multilayer adsorption mechanism. Notably, a substantial reduction in parameters such as Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) was also achieved up to 62 % and 79 %, respectively. Therefore, the developed adsorbent could be suggested as a viable candidate for eliminating dyes from the wastewater, especially from the tannery effluent.

Molecular mechanism of thiamine in mitigating drought stress in Chinese wingnut (Pterocarya stenoptera): Insights from transcriptomics

Urban garden plants are frequently affected by drought, which can hinder their growth, development, and greening effect. Previous studies have indicated that Chinese wingnut (Pterocarya stenoptera) responds to drought stress by increasing the expression of thiamine synthesis genes. In this study, it was found that exogenous thiamine can effectively alleviate the negative effects of drought stress on plants. Forward transcriptome sequencing and physiological tests were further conducted to reveal the molecular mechanism of thiamine in alleviating drought stress. Results showed that exogenous thiamine activated the expression of eight chlorophyll synthesis genes in Chinese wingnut under drought stress. Moreover, physiological indicators proved that chlorophyll content increased in leaves of Chinese wingnut with thiamine treatment under drought stress. Photosynthesis genes were also activated in Chinese wingnut treated with exogenous thiamine under drought stress, as supported by photosynthetic indicators PIabs and PItotal. Additionally, exogenous thiamine stimulated the expression of genes in the auxin-activated signaling pathway, thus attenuating the effects of drought stress. This study demonstrates the molecular mechanism of thiamine in mitigating the effects of drought stress on non-model woody plants lacking transgenic systems. This study also provides an effective method to mitigate the negative impacts of drought stress on plants.

Harnessing enzyme cofactors and plant metabolism: an essential partnership

Cofactors are fundamental to the catalytic activity of enzymes. Additionally, because plants are a critical source of several cofactors (i.e., including their vitamin precursors) within the context of human nutrition, there have been several studies aiming to understand the metabolism of coenzymes and vitamins in plants in detail. For example, compelling evidence has been brought forth regarding the role of cofactors in plants; specifically, it is becoming increasingly clear that an adequate supply of cofactors in plants directly affects their development, metabolism, and stress responses. Here, we review the state-of-the-art knowledge on the significance of coenzymes and their precursors with regard to general plant physiology and discuss the emerging functions attributed to them. Furthermore, we discuss how our understanding of the complex relationship between cofactors and plant metabolism can be used for crop improvement.

Calcium lignosulfonate modulates physiological and biochemical responses to enhance shoot multiplication in Vanilla planifolia Andrews

Utilisation of calcium lignosulfonate (CaLS) in Vanilla planifolia has been reported to improve shoot multiplication. However, mechanisms responsible for such observation remain unknown. Here, we elucidated the underlying mechanisms of CaLS in promoting shoot multiplication of V. planifolia via comparative proteomics, biochemical assays, and nutrient analysis. The proteome profile of CaLS-treated plants showed enhancement of several important cellular metabolisms such as photosynthesis, protein synthesis, Krebs cycle, glycolysis, gluconeogenesis, and carbohydrate synthesis. Further biochemical analysis recorded that CaLS increased Rubisco activity, hexokinase activity, isocitrate dehydrogenase activity, total carbohydrate content, glutamate synthase activity and total protein content in plant shoot, suggesting the role of CaLS in enhancing shoot growth via upregulation of cellular metabolism. Subsequent nutrient analysis showed that CaLS treatment elevated the contents of several nutrient ions especially calcium and sodium ions. In addition, our study also revealed that CaLS successfully maintained the cellular homeostasis level through the regulation of signalling molecules such as reactive oxygen species and calcium ions. These results demonstrated that the CaLS treatment can enhance shoot multiplication in V. planifolia Andrews by stimulating nutrient uptake, inducing cell metabolism, and regulating cell homeostasis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01293-w.

Optimization of nucleic acid extraction and amplification of a thiamine biosynthesis gene fragment from selected Malaysian seaweeds

Obtaining high-quality nucleic acid extracted from seaweeds is notoriously difficult due to contamination with polysaccharides and polyphenolic compounds after cell disruption. Specific methods need to be employed for RNA isolation in different seaweed species, and therefore studies of the thiamine biosynthesis pathway have been limited. Two selected Malaysian species which are highly abundant and underutilized, namely Gracilaria sp. and Padina sp., representing the red and brown seaweeds, respectively, were collected to develop optimized total RNA extraction methods. Prior to that, DNA was extracted, and amplification of the 18S rRNA gene and the THIC gene (encoding the first enzyme in the pyrimidine branch of the thiamine biosynthesis pathway) from the DNA template was successful in Gracilaria sp. only. RNA was then extracted from both seaweeds using three different existing methods, with some modifications, using cetyltrimethylammonium bromide, guanidine thiocyanate and sodium dodecyl sulphate. Methods I and III proved to be efficient for Padina sp. and Gracilaria sp., respectively, for the extraction of highly purified RNA, with A₂₆₀/A₂₈₀ values of 2.0 and 1.8. However, amplification of the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase and the THIC gene was successful in only Gracilaria sp. cDNA derived from extracted RNA. Further modifications are required to improve the exploitation of nucleic acids from brown seaweeds, which has been proven to be difficult. This work should pave the way for molecular studies of seaweeds generally and for the elucidation, specifically, of the thiamine biosynthesis pathway.

Biofortification: A long-term solution to improve global health- a review

Biofortification is a revolutionary technique for improving plant nutrition and alleviating human micronutrient deficiency. Fertilizers can help increase crop yield and growth, but applying too much fertilizer can be a problem because it leads to the release of greenhouse gases and eutrophication. One of the major global hazards that affects more than two million people globally is the decreased availability of micronutrients in food crops, which results in micronutrient deficiencies or "hidden hunger" in people. Micronutrients, like macronutrients, perform a variety of roles in plant and human nutrition. This review has highlighted the importance of micronutrients as well as their advantages. The uneven distribution of micronutrients in geological areas is not the only factor responsible for micronutrient deficiencies, other parameters including soil moisture, temperature, texture of the soil, and soil pH significantly affects the micronutrient concentration and their availability in the soil. To overcome this, different biofortification approaches are assessed in the review in which microbes mediated, Agronomic approaches, Plant breeding, and transgenic approaches are discussed. Hidden hunger can result in risky health conditions and diseases such as cancer, cardiovascular disease, osteoporosis, neurological disorders, and many more. Microbes-mediated biofortification is a novel and promising solution for the bioavailability of nutrients to plants in order to address these problems. Biofortification is cost effective, feasible, and environmentally sustainable. Bio-fortified crops boost our immunity, which helps us to combat these deadly viruses. The studies we discussed in this review have demonstrated that they can aid in the alleviation of hidden hunger.

The cultivable endophytic fungal community of Scutellaria baicalensis: diversity and relevance to flavonoid production by the host

Scutellaria baicalensis (SB), a traditional Chinese medicinal plant, is widely used because of its important pharmacological activities. However, the endophytic fungi that promote flavonoid accumulation in SB remain unclear. Therefore, we analyzed the endophytic fungal community of SB and screened the endophytic fungi that might promote flavonoid synthesis in SB. ITS1/ITS4Blast was used to identify the endophytic fungi in SB. In total, 687 strains were identified in 57 genera. The dominant genus in the leaves and stems was Alternaria and that in the roots was Fusarium. Alternaria was the dominant genus in SB collected from all sites and in wild and cultivated SB. Alpha diversity indexes indicated more abundant endophytic fungi in samples from Chengde, the genuine producing area of SB, than in those from other sites. Beta diversity index analysis indicated that SB plants with closer geographical relationships showed more similar endophytic fungal community profiles. Spearman correlation analysis revealed that baicalin, wogonoside, wogonin, and oroxylin A contents were significantly correlated with the relative abundance of Alternaria. Overall, the results indicate the importance of geographical factors in influencing the endophytic fungal community of SB and suggest that the presence of Alternaria spp. might contribute to flavonoid synthesis in SB.

The temporal and spatial endophytic fungal community of Huperzia serrata: diversity and relevance to huperzine A production by the host

BACKGROUND

Plants maintain the steady-state balance of the mutually beneficial symbiosis relationship with their endophytic fungi through secondary metabolites. Meanwhile endophytic fungi can serve as biological inducers to promote the biosynthesis and accumulation of valuable secondary metabolites in host plants through a variety of ways. The composition and structure of endophytic fungal community are affected by many factors, including tissues, seasons and so on. In this work, we studied the community diversity, temporal and spatial pattern of endophytic fungi detected from the roots, stems and leaves of Huperzia serrata in different seasons. The correlation between endophytic fungi and huperzine A (HupA) content in plants was analyzed.

RESULTS

A total of 7005 operational taxonomic units were detected, and all strains were identified as 14 phyla, 54 classes, 140 orders, 351 families and 742 genera. Alpha diversity analysis showed that the diversity of endophytic fungi in stem and leaf was higher than that in root, and the diversity in summer (August) was lower than that in other months. NMDS analysis showed that the endophytic fungal communities of leaves, stems and roots were significantly different, and the root and leaf communities were also different between four seasons. Through correlation analysis, it was found that 33 genera of the endophytic fungi of H. serrata showed a significant positive correlation with the content of HupA (p < 0.05), of which 13 genera (Strelitziana, Devriesia, Articulospora, Derxomyces, Cyphellophora, Trechispora, Kurtzmanomyces, Capnobotryella, Erythrobasidium, Camptophora, Stagonospora, Lachnum, Golubevia) showed a highly significant positive correlation with the content of HupA (p < 0.01). These endophytic fungi may have the potential to promote the biosynthesis and accumulation of HupA in plant.

CONCLUSIONS

This report is the first time to analyze the diversity of endophytic fungi in tissues of H. serrata in different seasons, which proves that there is variability in different tissues and seasonal distribution patterns. These findings provide references to the study of endophytic fungi of H. serrata.

λ-Carrageenan promotes plant growth in banana via enhancement of cellular metabolism, nutrient uptake, and cellular homeostasis

Banana (Musa acuminata) is an important fruit crop and source of income for various countries, including Malaysia. To date, current agrochemical practice has become a disputable issue due to its detrimental effect on the environment. λ-carrageenan, a natural polysaccharide extracted from edible red seaweed, has been claimed to be a potential plant growth stimulator. Hence, the present study investigates the effects of λ-carrageenan on plant growth using Musa acuminata cv. Berangan (AAA). Vegetative growth such as plant height, root length, pseudostem diameter, and fresh weight was improved significantly in λ-carrageenan-treated banana plants at an optimum concentration of 750 ppm. Enhancement of root structure was also observed in optimum λ-carrageenan treatment, facilitating nutrients uptake in banana plants. Further biochemical assays and gene expression analysis revealed that the increment in growth performance was consistent with the increase of chlorophyll content, protein content, and phenolic content, suggesting that λ-carrageenan increases photosynthesis rate, protein biosynthesis, and secondary metabolites biosynthesis which eventually stimulate growth. Besides, λ-carrageenan at optimum concentration also increased catalase and peroxidase activities, which led to a significant reduction in hydrogen peroxide and malondialdehyde, maintaining cellular homeostasis in banana plants. Altogether, λ-carrageenan at optimum concentration improves the growth of banana plants via inducing metabolic processes, enhancing nutrient uptake, and regulation of cell homeostasis. Further investigations are needed to evaluate the effectiveness of λ-carrageenan on banana plants under field conditions.

The Vital Role of ShTHIC from the Endophyte OsiSh-2 in Thiamine Biosynthesis and Blast Resistance in the OsiSh-2-Rice Symbiont

Endophytes can benefit the growth and stress resistance of host plants by secreting bioactive components. Thiamine is an essential vitamin involved in many metabolic pathways and can only be synthesized by microbes and plants. In this study, we found that thiamine could inhibit the development of the phytopathogen Magnaporthe oryzae and decrease the rice blast index under field conditions. In the thiamine biosynthesis pathway, the key enzyme ShTHIC of an endophyte Streptomyces hygroscopicus OsiSh-2 and OsTHIC of rice (Oryza sativa) were highly homologous. Gene overexpression or knockout approaches revealed that both THIC contributed to thiamine synthesis and resistance to M. oryzae. Furthermore, S. hygroscopicus OsiSh-2 colonization led to a decrease in the thiamine synthesis level of rice but still maintained thiamine homeostasis in rice. However, inoculation with the ShTHIC knockout strain ΔTHIC reduced the thiamine content in rice, although the thiamine synthesis level of rice was increased. After infection with M. oryzae, blast resistance was dramatically improved in OsiSh-2-inoculated rice but decreased in ΔTHIC-inoculated rice compared with non-inoculated rice. This result demonstrated that ShTHIC could regulate thiamine biosynthesis and consequently assist blast resistance in the OsiSh-2-rice symbiont. Our results revealed a novel blast-resistance mechanism mediated by a key thiamine biosynthetic enzyme from an endophyte OsiSh-2.

Thiamin stimulates growth, yield quality and key biochemical processes of cauliflower (Brassica oleracea L. var. Botrytis) under arid conditions

Thiamin is a crucial vitamin with a vast variety of anti-oxidative and physiological roles in plants subjected to abiotic stresses. We examined the efficiency of foliar-applied thiamin (50 and 100 mM) on growth, yield quality and key-biochemical characteristics of two cultivars (FD1 and FD3) of cauliflower (Brassica oleracea L.) under water-deficit stress. Water stress at the rate of 50% field capacity (F.C.) markedly decreased the plant biomass, leaf total phenolics and ascorbic acid (AsA) contents. In contrast, drought-induced increase was noted in the leaf [hydrogen peroxide (H2O2), AsA, proline, malondialdehyde (MDA), glycinebetaine (GB), total soluble proteins and oxidative defense system in terms of high activities of peroxidase (POD), and catalase (CAT) enzymes] and the inflorescence (total phenolics, proline, GB, MDA, H2O2, and activities of SOD and CAT enzymes) characteristics of cauliflower. However, foliar-applied thiamin significantly improved growth and physio-biochemical attributes except leaf and inflorescence MDA and H2O2 contents of both cauliflower cultivars under water stress. Overall, application of thiamin enhanced the plant growth may be associated with suppressed reactive oxygen species (ROS) and upregulated antioxidants defense system of cauliflower.

A novel panel of yeast assays for the assessment of thiamin and its biosynthetic intermediates in plant tissues

Thiamin (or thiamine), known as vitamin B1, represents an indispensable component of human diets, being pivotal in energy metabolism. Thiamin research depends on adequate vitamin quantification in plant tissues. A recently developed quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is able to assess the level of thiamin, its phosphorylated entities and its biosynthetic intermediates in the model plant Arabidopsis thaliana, as well as in rice. However, their implementation requires expensive equipment and substantial technical expertise. Microbiological assays can be useful in deter-mining metabolite levels in plant material and provide an affordable alternative to MS-based analysis. Here, we evaluate, by comparison to the LC-MS/MS reference method, the potential of a carefully chosen panel of yeast assays to estimate levels of total vitamin B1, as well as its biosynthetic intermediates pyrimidine and thiazole in Arabidopsis samples. The examined panel of Saccharomyces cerevisiae mutants was, when implemented in microbiological assays, capable of correctly assigning a series of wild-type and thiamin biofortified Arabidopsis plant samples. The assays provide a readily applicable method allowing rapid screening of vitamin B1 (and its biosynthetic intermediates) content in plant material, which is particularly useful in metabolic engineering approaches and in germplasm screening across or within species.

Comprehensive Identification and Profiling of miRNAs Involved in Terpenoid Synthesis of Gleditsia sinensis Lam

Gleditsia sinensis Lam. is a tree with worldwide distribution and important economic and medicinal values; its pods contain terpenoids including gleditsioside, thiamine, and brassinosteroids. However, thus far, there are few studies on the terpenoid regulation of G. sinensis at the molecular level. microRNA (miRNA) is a class of small RNAs with conserved and crucial roles in the regulation of diverse biological processes during plant growth and development. To identify the miRNAs of G. sinensis and evaluate their involvement in terpenoid synthesis, this investigation quantified the content changes in saponins in pods at three developmental stages: May (pod-setting stage), July (elongation stage), and September (browning stage), and then we performed genome-wide miRNA profiles during the three development stages of the G. sinensis pods. A total of 351 conserved miRNAs belonging to 216 families were identified, among which 36 conserved miRNAs exist specifically in legumes. Through target analysis, 708 unigenes were predicted to be candidate targets of 37 differentially expressed miRNAs. The targets of miR838-3p and miR2093-5p were involved in the derived branches of monoterpenes and gleditsioside, in brassinosteroid biosynthesis (BRB), and in indole alkaloid biosynthesis (IAB). Intriguingly, the targets of miR829-3p.1 were predicted to take part in thiamine biosynthesis, and the targets of miR4414b and miR5037a were involved in the main process of cytokinin synthesis. The corresponding targets participated in BRB, IAB, and terpenoid backbone biosynthesis, which were enriched significantly, suggesting that miR2093-5p, miR4414b, miR5037a, miR829-3p.1, and miR838-3p play indispensable roles in the regulation of triterpenoid saponin and monoterpenoid biosynthesis. To date, this is the first report of miRNA identification in G. sinensis and miRNA expression profiles at different developmental stages of G. sinensis pods, which provides a basis for further uncovering the molecular regulation of terpenoid synthesis in G. sinensis and new insights into the role of miRNAs in legumes.

Metabolic engineering provides insight into the regulation of thiamin biosynthesis in plants

Thiamin (or thiamine) is a water-soluble B-vitamin (B1), which is required, in the form of thiamin pyrophosphate, as an essential cofactor in crucial carbon metabolism reactions in all forms of life. To ensure adequate metabolic functioning, humans rely on a sufficient dietary supply of thiamin. Increasing thiamin levels in plants via metabolic engineering is a powerful strategy to alleviate vitamin B1 malnutrition and thus improve global human health. These engineering strategies rely on comprehensive knowledge of plant thiamin metabolism and its regulation. Here, multiple metabolic engineering strategies were examined in the model plant Arabidopsis thaliana. This was achieved by constitutive overexpression of the three biosynthesis genes responsible for B1 synthesis, HMP-P synthase (THIC), HET-P synthase (THI1), and HMP-P kinase/TMP pyrophosphorylase (TH1), either separate or in combination. By monitoring the levels of thiamin, its phosphorylated entities, and its biosynthetic intermediates, we gained insight into the effect of either strategy on thiamin biosynthesis. Moreover, expression analysis of thiamin biosynthesis genes showed the plant's intriguing ability to respond to alterations in the pathway. Overall, we revealed the necessity to balance the pyrimidine and thiazole branches of thiamin biosynthesis and assessed its biosynthetic intermediates. Furthermore, the accumulation of nonphosphorylated intermediates demonstrated the inefficiency of endogenous thiamin salvage mechanisms. These results serve as guidelines in the development of novel thiamin metabolic engineering strategies.

The importance of thiamine (vitamin B1) in plant health: From crop yield to biofortification

Ensuring that people have access to sufficient and nutritious food is necessary for a healthy life and the core tenet of food security. With the global population set to reach 9.8 billion by 2050, and the compounding effects of climate change, the planet is facing challenges that necessitate significant and rapid changes in agricultural practices. In the effort to provide food in terms of calories, the essential contribution of micronutrients (vitamins and minerals) to nutrition is often overlooked. Here, we focus on the importance of thiamine (vitamin B1) in plant health and discuss its impact on human health. Vitamin B1 is an essential dietary component, and deficiencies in this micronutrient underlie several diseases, notably nervous system disorders. The predominant source of dietary vitamin B1 is plant-based foods. Moreover, vitamin B1 is also vital for plants themselves, and its benefits in plant health have received less attention than in the human health sphere. In general, vitamin B1 is well-characterized for its role as a coenzyme in metabolic pathways, particularly those involved in energy production and central metabolism, including carbon assimilation and respiration. Vitamin B1 is also emerging as an important component of plant stress responses, and several noncoenzyme roles of this vitamin are being characterized. We summarize the importance of vitamin B1 in plants from the perspective of food security, including its roles in plant disease resistance, stress tolerance, and crop yield, and review the potential benefits of biofortification of crops with increased vitamin B1 content to improve human health.

Identification and characterisation of thiamine pyrophosphate (TPP) riboswitch in Elaeis guineensis

The oil palm (Elaeis guineensis) is an important crop in Malaysia but its productivity is hampered by various biotic and abiotic stresses. Recent studies suggest the importance of signalling molecules in plants in coping against stresses, which includes thiamine (vitamin B1). Thiamine is an essential microelement that is synthesized de novo by plants and microorganisms. The active form of thiamine, thiamine pyrophosphate (TPP), plays a prominent role in metabolic activities particularly as an enzymatic cofactor. Recently, thiamine biosynthesis pathways in oil palm have been characterised but the search of novel regulatory element known as riboswitch is yet to be done. Previous studies showed that thiamine biosynthesis pathway is regulated by an RNA element known as riboswitch. Riboswitch binds a small molecule, resulting in a change in production of the proteins encoded by the mRNA. TPP binds specifically to TPP riboswitch to regulate thiamine biosynthesis through a variety of mechanisms found in archaea, bacteria and eukaryotes. This study was carried out to hunt for TPP riboswitch in oil palm thiamine biosynthesis gene. Riboswitch detection software like RiboSW, RibEx, Riboswitch Scanner and Denison Riboswitch Detector were utilised in order to locate putative TPP riboswitch in oil palm ThiC gene sequence that encodes for the first enzyme in the pyrimidine branch of the pathway. The analysis revealed a 192 bp putative TPP riboswitch located at the 3' untranslated region (UTR) of the mRNA. Further comparative gene analysis showed that the 92-nucleotide aptamer region, where the metabolite binds was conserved inter-species. The secondary structure analysis was also carried out using Mfold Web server and it showed a stem-loop structure manifested with stems (P1-P5) with minimum free energy of -12.26 kcal/mol. Besides that, the interaction of riboswitch and its ligand was determined using isothermal titration calorimetry (ITC) and it yielded an exothermic reaction with 1:1 stoichiometry interaction with binding affinities of 0.178 nM, at 30°C. To further evaluate the ability of riboswitch to control the pathway, exogenous thiamine was applied to four months old of oil palm seedlings and sampling of spear leaves tissue was carried out at days 0, 1, 2 and 3 post-treatment for expression analysis of ThiC gene fragment via quantitative polymerase chain reaction (qPCR). Results showed an approximately 5-fold decrease in ThiC gene expression upon application of exogenous thiamine. Quantification of thiamine and its derivatives was carried out via HPLC and the results showed that it was correlated to the down regulation of ThiC gene expression. The application of exogenous thiamine to oil palm affected ThiC gene expression, which supported the prediction of the presence of TPP riboswitch in the gene. Overall, this study provides the first evidence on the presence, binding and the functionality of TPP riboswitch in oil palm. This study is hoped to pave a way for better understanding on the regulation of thiamine biosynthesis pathway in oil palm, which can later be exploited for various purposes especially in manipulation of thiamine biosynthesis pathways in combating stresses in oil palm.

Time-series expression profiling of sugarcane leaves infected with Puccinia kuehnii reveals an ineffective defense system leading to susceptibility

Successful orange rust development on sugarcane can potentially be explained as suppression of the plant immune system by the pathogen or delayed plant signaling to trigger defense responses. Puccinia kuehnii is an obligate biotrophic fungus that infects sugarcane leaves causing a disease called orange rust. It spread out to other countries resulting in reduction of crop yield since its first outbreak. One of the knowledge gaps of that pathosystem is to understand the molecular mechanisms altered in susceptible plants by this biotic stress. Here, we investigated the changes in temporal expression of transcripts in pathways associated with the immune system. To achieve this purpose, we used RNA-Seq to analyze infected leaf samples collected at five time points after inoculation. Differential expression analyses of adjacent time points revealed substantial changes at 12, 48 h after inoculation and 12 days after inoculation, coinciding with the events of spore germination, haustoria post-penetration and post-sporulation, respectively. During the first 24 h, a lack of transcripts involved with resistance mechanisms was revealed by underrepresentation of hypersensitive and defense response related genes. However, two days after inoculation, upregulation of genes involved with immune response regulation provided evidence of some potential defense response. Events related to biotic stress responses were predominantly downregulated in the initial time points, but expression was later restored to basal levels. Genes involved in carbohydrate metabolism showed evidence of repression followed by upregulation, possibly to ensure the pathogen nutritional requirements were met. Our results support the hypothesis that P. kuehnii initially suppressed sugarcane genes involved in plant defense systems. Late overexpression of specific regulatory pathways also suggests the possibility of an inefficient recognition system by a susceptible sugarcane genotype.

24-Epibrassinolide alters DNA cytosine methylation of Linum usitatissimum L. under salinity stress

Salinity is a common environmental challenge limiting worldwide agricultural crop yield. Plants employ epigenetic regulatory strategies, such as DNA methylation which relatively allows rapid adaptation to new conditions in response to environmental stresses. Brassinosteroids (BRs) are a novel group of phytohormones recognized as transcription and translation regulators which are able to mitigate the impact of environmental stresses on the plants. In the current investigation, the influence of salinity and 24-epibrassinolide (24-epiBL) was investigated on the extent and pattern of cytosine DNA methylation using methylation-sensitive amplified polymorphisms (MSAP) technique in flax. Upon NaCl (150 mM) exposure, total methylation of CCGG sequences was decreased in comparison to control plants, while 24-epiBL (10^-8 M) induced total methylation under salinity stress. Sequencing and analysis of six randomly selected MSAP fragments detected genes involved in various biological and molecular processes such as vitamine B1 biosynthesis, protein targeting and localization, post-translational modification and gene regulation. In conclusion, 24-epiBL seed priming could play critical role in regulation of cellular and biological processes in response to salt stress by epigenetic modification and induction of methylation.

Chitosan nanoparticles loaded with thiamine stimulate growth and enhances protection against wilt disease in Chickpea

Nanoencapsulation is considered as one of the unique technique for increasing the bioavailability, solubility and retention time of bioactive compounds. In this study, thiamine was incorporated into the chitosan nanoparticles and characterized through FTIR, DLS, SEM, TEM and XRD analyses. Zeta potential of the synthesized nanoparticles was found to be 37.7 mV. The encapsulation efficiency of chitosan nanoparticle was 90 ± 3%. Application of thiamine loaded chitosan nanoparticle enhanced seed germination and growth of chickpea seedlings when compared to untreated control seeds. Treated seedlings showed enhanced production of indole acetic acid (IAA). Foliar application of synthesized nanoparticle induced defense enzymes in leaves and roots of chickpea plants. Decreased cell death in the chickpea roots of treated plants was observed when compared to control under green house condition. These results showed that the thiamine loaded chitosan nanoparticle can be used as a growth stimulator as well as a defense activator in chickpea.

Toward Eradication of B-Vitamin Deficiencies: Considerations for Crop Biofortification

'Hidden hunger' involves insufficient intake of micronutrients and is estimated to affect over two billion people on a global scale. Malnutrition of vitamins and minerals is known to cause an alarming number of casualties, even in the developed world. Many staple crops, although serving as the main dietary component for large population groups, deliver inadequate amounts of micronutrients. Biofortification, the augmentation of natural micronutrient levels in crop products through breeding or genetic engineering, is a pivotal tool in the fight against micronutrient malnutrition (MNM). Although these approaches have shown to be successful in several species, a more extensive knowledge of plant metabolism and function of these micronutrients is required to refine and improve biofortification strategies. This review focuses on the relevant B-vitamins (B1, B6, and B9). First, the role of these vitamins in plant physiology is elaborated, as well their biosynthesis. Second, the rationale behind vitamin biofortification is illustrated in view of pathophysiology and epidemiology of the deficiency. Furthermore, advances in biofortification, via metabolic engineering or breeding, are presented. Finally, considerations on B-vitamin multi-biofortified crops are raised, comprising the possible interplay of these vitamins in planta.