Total Carotenoid Accumulation Research Articles

Carotenoid biosynthesis genes LcLCYB, LcLCYE, and LcBCH from wolfberry confer increased carotenoid content and improved salt tolerance in tobacco

Carotenoids play essential roles in plant growth and development and provide plants with a tolerance to a series of abiotic stresses. In this study, the function and biological significance of lycopene β-cyclase, lycopene ε-cyclase, and β-carotene hydroxylase, which are responsible for the modification of the tetraterpene skeleton procedure, were isolated from Lycium chinense and analyzed. The overexpression of lycopene β-cyclase, lycopene ε-cyclase, and β-carotene hydroxylase promoted the accumulation of total carotenoids and photosynthesis enhancement, reactive oxygen species scavenging activity, and proline content of tobacco seedlings after exposure to the salt stress. Furthermore, the expression of the carotenoid biosynthesis genes and stress-related genes (ascorbate peroxidase, catalase, peroxidase, superoxide dismutase, and pyrroline-5-carboxylate reductase) were detected and showed increased gene expression level, which were strongly associated with the carotenoid content and reactive oxygen species scavenging activity. After exposure to salt stress, the endogenous abscisic acid content was significantly increased and much higher than those in control plants. This research contributes to the development of new breeding aimed at obtaining stronger salt tolerance plants with increased total carotenoids and vitamin A content.

Effects of high dietary inclusion of Arthrospira platensis, either extruded or supplemented with a super-dosing multi-enzyme mixture, on broiler growth performance and major meat quality parameters

BackgroundThis investigation assessed the effects of high dietary inclusion of Spirulina (Arthrospira platensis) on broiler chicken growth performance, meat quality and nutritional attributes. For this, 120 male broiler chicks were housed in 40 battery brooders (three birds per brooder). Initially, for 14 days, a standard corn and soybean meal diet was administered. Subsequently, from days 14 to 35, chicks were assigned to one of the four dietary treatments (n = 10 per treatment): (1) control diet (CTR); (2) diet with 15% Spirulina (SP); (3) diet with 15% extruded Spirulina (SPE); and (4) diet with 15% Spirulina plus a super-dosing enzymes supplement (0.20% pancreatin extract and 0.01% lysozyme) (SPM).ResultsThroughout the experimental period, both SP and SPM diets resulted in decreased final body weight and body weight gain compared to control (p < 0.001), with the SPE diet showing comparable results to CTR. The SPE diet prompted an increase in average daily feed intake (p = 0.026). However, all microalga treatments increased the feed conversion ratio compared to CTR. Dietary inclusion of Spirulina notably increased intestinal content viscosity (p < 0.010), which was mitigated by the SPM diet. Spirulina supplementation led to lower pH levels in breast meat 24 h post-mortem and heightened the b* colour value in both breast and thigh meats (p < 0.010). Furthermore, Spirulina contributed to an increased accumulation of total carotenoids, n-3 polyunsaturated fatty acids (PUFA), and saturated fatty acids (SFA), while diminishing n-6 PUFA, thus altering the n-6/n-3 and PUFA/SFA ratios favourably (p < 0.001). However, it also reduced zinc concentration in breast meat (p < 0.001).ConclusionsThe findings indicate that high Spirulina levels in broiler diets impair growth due to increased intestinal viscosity, and that extrusion pre-treatment mitigates this effect. Despite reducing digesta viscosity, a super-dosing enzyme mix did not improve growth. Data also indicates that Spirulina enriches meat with antioxidants and n-3 PUFA but reduces α-tocopherol and increases saturated fats. Reduced zinc content in meat suggests the need for Spirulina biofortification to maintain its nutritional value.

Accumulation of β-citraurin and other carotenoids in relation to the expression of PSY1 and CCD4b1 in peel of twelve red-peeled citrus cultivars

Peel color in citrus is largely genetically controlled. Red peel is favored by customers and is important, therefore, for fruit external quality. In order to understand the factors affecting distribution of carotenoids and color intensity of red-peeled citrus, we compared carotenoid accumulation and gene expression in the peel of twelve fully ripe red-peeled citrus cultivars with different genetic backgrounds. The results showed that β-citraurin, a red C30 carotenoid, was the second or third most abundant colored carotenoid in the peel of all twelve red-peeled citrus, ranging from 9.4 % to 26.7 % of total carotenoids. Statistical analysis of carotenoid composition and content showed that of the main carotenoids β-citraurin had the highest correlation with red appearance of cultivars. In addition, β-cryptoxanthin, which accounted for 3.6 % to 16.4 % of the total carotenoids, were also significantly positively correlated with citrus color index (CCI). The expression of two key genes, phytoene synthase 1 (PSY1) and carotenoid cleavage dioxygenase 4b1 (CCD4b1), differed among cultivars with a range of 3.5- and 48.8-fold, respectively. Surprisingly, accumulation of total carotenoids and β-citraurin was not correlated with the expression of PSY1 and CCD4b1, respectively, implying that diverse factors influence high carotenoid accumulation in red-peeled citrus.

Layer by layer application of chitosan and carboxymethyl cellulose coatings delays ripening of mango fruit by suppressing cell wall polysaccharides disassembly

Mango is a climacteric fruit that ripens quickly after harvest due to its climacteric nature. Edible coatings have been reported to delay the ripening of various harvested fruit. The efficacy of the applied edible coatings could be improved by using in combination as a layer-by-layer (LBL) approach. So, the influence of LBL application of chitosan (CH) and carboxymethyl cellulose (CMC) was studied on mangoes during postharvest storage at 15 °C for 20 days. Mangoes were coated with monolayers of CH (1 % w/v) and CMC (1 % w/v) as well as LBL application of CH and CMC and were compared with control. The treatment of mangoes with CH and CMC-based LBL treatment resulted in lower decay percentage and weight loss along with higher total chlorophyll pigments and suppressed total carotenoid accumulation. The LBL application of CH and CMC showed lower activity of chlorophyll degrading such as chlorophyllase (CPS), pheophytinase (Phe), Mg-dechalatase (MGD) and chlorophyll degrading peroxidase (Chl-POD) enzymes as well as reduced changes in b*, a* and L* along with a suppressed increase in ethylene (EP) and CO2 production (CPR) rates having higher antioxidant such as catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and superoxide dismutase (SOD) enzymes activity. In addition, mangoes coated with LBL treatment of CH and CMC exhibited lower water-soluble pectin (WSP) and higher protopectin (PP) having higher concentrations of chelate soluble (CSP) and sodium carbonate-soluble pectin (SCP). Similarly, LBL-coated mangoes showed significantly higher hemicellulose (HCLS) and cellulose (CLS) contents in contrast with control. It was observed that mangoes coated with CH and CMC-based LBL coating exhibited higher flesh firmness and showed suppressed cellulase (CS), pectin methylesterase (PME), polygalacturonase (PG) and β-galactosidase (β-Gal) enzymes activity. The concentrations of total soluble solids and ripening index were markedly lower and titratable acidity was higher in the LBL-based coating treatment in comparison with control. In conclusion, LBL treatment based on CH and CMC coatings could be used for the delay of ripening and softening of harvested mangoes.

Trihelix transcription factor SlGT31 regulates fruit ripening mediated by ethylene in tomato.

Trihelix proteins are plant-specific transcription factors that play crucial roles in plant development and stress responses. However, the involvement of trihelix proteins in fruit ripening and transcriptional regulatory mechanisms remains largely unclear. In this study, we cloned a trihelix gene SlGT31, whose relative expression was significantly induced by the application of exogenous ethylene but repressed by 1-methylcyclopropene (1-MCP). Suppression of SlGT31 resulted in delayed fruit ripening, decreased accumulation of total carotenoids and ethylene content, and inhibition of relative expression of genes related to ethylene and fruit ripening. Conversely, the opposite results were observed in SlGT31-overexpression lines. Yeast one-hybrid and dual-luciferase assays suggested that SlGT31 could bind to the promoters of two key ethylene biosynthesis genes ACO1 and ACS4. These results indicate that SlGT31 may act as a positive modulator during fruit ripening.

Effect of growing season on some qualitative and functional attributes of different potato genotypes

AbstractPotato (Solanum tuberosumL.) is a staple food widely consumed in Tunisia and a source of nutrients beneficial for human health. The tubers are, indeed, important source of vitamins, minerals, and bioactive compounds, including carotenoids, polyphenols, and flavonoids. However, data regarding the functional quality of potato varieties grown and consumed in Tunisia are very scarce. For this reason, two field trials were conducted to focus on the effect of the growing season on the functional quality of four potato genotypes (Selena, El Beidha, Naima, and CL07F172.5): a first autumnal trial in Teboulba, Monastir (September 2015–February 2016), which is the late cropping season (LCS) and a second summer cropping season (SCS) in El ksour, El Kef region at an altitude &gt; 1000 m (July 2015–October 2015). Total carotenoids, total phenolics, and flavonoids contents, as well as the hydrophilic radical scavenging activity and lipophilic radical scavenging activity (LRSA) were determined. The obtained results confirmed the importance of potato tubers as a source of bioactive compounds. All quality traits varied significantly among varieties and cropping seasons. Tubers grown under colder weather conditions (LCS: minimum and maximum averages temperatures and relative humidity (RH) ranging between 14.25 and 22.55°C and 25.46% and 83.07%, respectively) accumulated the highest total vitamin C content and exhibited the highest LRSA values. However, temperature and warmer growing conditions (SCS: minimum and maximum averages temperatures and RH ranging between 19.74 and 34.22°C and 35.46% and 87.51%, respectively) probably enhanced the synthesis and accumulation of total carotenoids, total phenolics, and total flavonoids, associated with higher LRSA values.

Biocomposite Coatings Delay Senescence in Stored Diospyros kaki Fruits by Regulating Antioxidant Defence Mechanism and Delaying Cell Wall Degradation

Climacteric rise in the rate of respiration and ethylene production in harvested persimmon (Diospyros kaki) fruits leads to early onset of fruit tissue senescence. Therefore, this study was carried out to maintain the quality of stored persimmons by using edible coatings. For this purpose, Aloe vera gel was combined with food hydrocolloids, gum arabic or tragacanth gum, and applied on persimmon fruits that were stored for 20 days at 20 ± 1 °C and 80–85% RH. Biocomposite coatings, compared to control, remarkably reduced weight loss, decay incidence, respiration rate, ethylene production, electrolyte leakage, malondialdehyde, H2O2 and superoxide anion content in stored fruits. The use of composite coatings inhibited colour change by reducing the accumulation of total carotenoids, maintained higher antioxidative enzymes activity and suppressed the activity of cell wall degrading enzymes, resultantly preserving cell wall components. Composite coated fruits exhibited the least change in biochemical attributes and higher sensory scores in comparison with non-coated fruits at the end of the storage period. In conclusion, Aloe vera gel/gum arabic was the most effective coating treatment before storing persimmons.

Knockdown of Sly-miR160a using short tandem target mimic (STTM) enhanced expression of auxin signaling genes and delayed postharvest ripening of tomato fruit

The miR160 is a highly conserved microRNA (miRNA) that regulates the auxin signaling pathway through negative regulation of auxin response factors (ARFs) and plays pivotal roles in fruit development. In the present study, the knockdown of miR160a using short tandem target mimic (STTM 160a) and overexpression of miR160a (miR160a-OE) transgenic tomato lines were generated to investigate the possible roles of miR160 in postharvest ripening tomato fruit. The results showed that the STTM 160a increased total chlorophyll content, reduced lycopene and total carotenoid accumulation, weight loss, and respiration rate while increasing firmness in tomato fruit compared with the wild-type (WT) and miR160a-OE. Additionally, miR160a-OE lines exhibited a typical auxin hypersensitivity and postharvest ripening acceleration, whereas STTM 160a lines displayed an auxin hyposensitivity and postharvest ripening reduction. Moreover, the relative expression levels of ARF10A (Solyc11g069500.2.1), ARF10B (Solyc06g075150.3.1), ARF17 (Solyc11g013480.2.1), and Aux/IAA genes were up-regulated in STTM 160a lines. The results suggest that the knockdown of Sly-miR160a delays postharvest ripening in tomato fruit, and provide valuable information for genetic engineering in controlling developmental processes.

β-Carotene and lutein accumulation, and carotenoid biosynthetic gene expression during fruit development and fruit ripening of A genome banana

• β -carotene and lutein content, affecting to orange-yellow pulp color in KK2. • Expression of MaPSY2a gene in KK2 affected to carotenoids accumulation. • Carotenoid biosynthetic genes correlated with β -carotene and lutein level. • Difference of A genome composition in banana affects carotenoid accumulation. Bananas ( Musa spp.) are an important source of pro-vitamin A, derived from carotenoids. Some cultivated bananas originated from intra-specific hybridization resulting in genotypes which are diploid (AA) and triploid (AAA) genomes that are the most important bananas for desserts. The accumulation of carotenoids and transcripts of genes related to carotenoid biosynthesis during fruit development and ripening in cultivars carrying the banana A genome (AA and AAA) were investigated. The accumulation of total carotenoids was greatest in ‘Khai Kasetsart2’ (KK2; AA) and ‘Sa’ (SA; AA), and comparatively lower in other cultivars. The predominant carotenoids in this fruit were β- carotene and lutein, with a small amount of α- carotene, which correlate with the orange-yellow pulp color (in particular KK2). In contrast, Leb Mu Nang had the lowest total carotenoids during fruit development while lutein and β -carotene in Hom Thong increased with fruit ripening. MaPSY2a gene expression in KK2 and SA cultivars occurred throughout fruit development but declined during fruit ripening. The expression of MaLCYB, MaLCYE, MaCHYB , and MaCHYE genes increased throughout fruit development and during fruit ripening resulting in β- carotene and lutein high content. In cultivars with low carotenoid levels, MaLCYB gene expression was reduced, while the MaLCYE, MaCHYE, and MaCHYB genes were up-regulated during fruit ripening. Besides, the MaCCD4 gene (a gene associated with carotenoid turnover) had lower expression throughout fruit development and ripening in KK2 compared to the other cultivars. These results suggested that the different carotenoid accumulation patterns in the cultivars could be attributed to differential gene expression and A genome composition.

Pearl Grey Shading Net Boosts the Accumulation of Total Carotenoids and Phenolic Compounds That Accentuate the Antioxidant Activity of Processing Tomato.

Tomato (Solanum lycopersicum L.) is one of the most consumed vegetables worldwide due to its low caloric intake and high fiber, minerals, and phenolic compounds, making it a high-quality functional food. However, fruit quality attributes can be affected by pre-harvest factors, especially environmental stresses. This research aimed to evaluate the influence of two shading nets (white net −30% and pearl grey net −40% shading degree) on the yield and phytochemical profile of tomato fruits grown in summer under the Mediterranean climate. Mineral and organic acid content (by ion chromatography-IC), phenolic profile (by ultra-high performance liquid chromatography-UHPLC coupled with an Orbitrap high-resolution mass spectrometry-HRMS), carotenoid content (by high-performance liquid chromatography with diode array detection-HPLC-DAD), and antioxidant activities DPPH, ABTS, and FRAP (by UV-VIS spectrophotometry) were determined. Tomato fruits grown under the pearl grey net recorded the highest values of total phenolic compounds (14,997 µg 100 g−1 of fresh weight) and antioxidant activities DPPH, ABTS, and FRAP, without affecting either fruit color or marketable yield. The reduction of solar radiation through pearl grey nets proved to be an excellent tool to increase the phytochemical quality of tomato fruits during summer cultivation in a Mediterranean environment.

Chitosan-Phenylalanine Nanoparticles (Cs-Phe Nps) Extend the Postharvest Life of Persimmon (Diospyros kaki) Fruits under Chilling Stress

There are high levels of damage imposed on persimmon fruit postharvest, especially after storing it in cold storage, which causes chilling injury (CI). To reduce this stress on the fruit, the conventional way is to use chemical treatments. Since there is a limitation in the use of chemical materials, it is necessary to apply non-harmful treatments to decrease chilling injury and maintain the quality of persimmon in cold storage. The aim of this study is to investigate the effects of chitosan-loaded phenylalanine nanoparticles (Cs-Phe NPs) (2.5 and 5 mM) on physiochemical and quality factors of persimmon (Diospyros kaki) during 45 days of storage at 4 °C (38 °F) and evaluate the impact of Cs-Phe NPs on the preserving quality in order to reduce the chilling injury of this fruit. The experiment was conducted using a completely randomized design with three replications. Treatments were applied at 15, 30, and 45 days after storage at 4 °C with ≥90% relative humidity. The size of Cs-Phe NPs was less than 100 nm, approximately. The results showed that application of 5 mM of Cs-Phe NPs delayed the negative effects of chilling stress and enhanced antioxidant capacity, firmness, and total soluble solids of persimmon fruit. Lower H2O2 and malonaldehyde (MDA) accumulation along with higher soluble tannin and total carotenoid accumulation in persimmon fruit treated with 5 mM Cs-Phe NPs was also observed. Fruit coated using Cs-Phe NPs in both concentrations (2.5 and 5 mM) showed the highest antioxidant enzyme activity for superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) and the lowest for polyphenol oxidase (PPO) and chilling injury during storage. According to our results, 5 mM of Cs-Phe NPs could be considered as the best treatment under chilling-stress conditions.

Cloning and characterization ofRARs andRXRs from noble scallopChlamys nobilis, a bivalve rich in carotenoids

The noble scallop Chlamys nobilis that rich in carotenoids is one of the most popular scallop species for aquaculture. Very little is known whether bivalve SRB-like-3 gene expression is regulated by retinoic acid receptor (RAR) and/or retinoic X receptor (RXR). In this study, the full-length cDNA of RAR and RXR genes of C. nobilis was cloned and characterized for the first time, and then, the tissue differential expression of RAR and RXR mRNA in polymorphic C. nobilis was assessed. The roles of RAR and RXR in carotenoid accumulation in C. nobilis were assessed by manipulating the carotenoid content in tissues of C. nobilis via inhibiting the expression of SRB-like-3 gene. The results revealed that two isoforms of RAR (cnRARa (1958 bp/434 aa) and cnRARb (1901 bp/415 aa)) and four RXR isoforms (cnRXRa (1353-bp/450 aa), cnRXRb (1341-bp/446 aa), cnRXRc (1298-bp/436 aa) and cnRXRd (1286-bp/432 aa)) were cloned and characterized from C. nobilis. The reduction of carotenoid content caused by inhibition of SRB-like-3 gene induced the up-regulation of RAR and RXR genes, suggesting that RAR and RXR genes may play a role in the regulation of carotenoid accumulation in haemolymph of C. nobilis. The findings of this study provide important clues for the regulation mechanism of total carotenoid accumulation in C. nobilis.

Potential advancement of ultraviolet-free solar radiation technology in enriching the nutrient composition and biodiesel feedstock production in marine green microalga Platymonas subcordiformis

Outdoor cultivation was carried out on a site very near to the Tropic of Cancer (23°26′21.45″) to investigate the effects of solar radiation on the growth, nutrient composition and biodiesel feedstock production of a marine green microalga Platymonas subcordiformis. During a 7-day period of exposure to sunlight in the winter, ultraviolet-free solar radiation (UVFSR) significantly increased the accumulation of total carotenoids and individual carotenoids including zeaxanthin, fucoxanthin and violaxanthin in P. subcordiformis when compared with the full spectrum solar radiation (FSSR). UVFSR treatment also resulted in significantly higher levels of palmitoleic acid, a main biodiesel feedstock, and eicosapentaenoic acid in the microalga than that of FSSR. Removal of the ultraviolet spectrum from the solar radiation (UVFSR technology) show its potential advantage for increasing the production of microalgal nutrient components including carotenoids and specific polyunsaturated fatty acids, as well as biodiesel feedstock, for the applications of attractive bioresources.

The basic helix-loop-helix transcription factor bHLH95 affects fruit ripening and multiple metabolisms in tomato.

Ethylene signaling pathways regulate several physiological alterations that occur during tomato fruit ripening, such as changes in colour and flavour. The mechanisms underlying the transcriptional regulation of genes in these pathways remain unclear, although the role of the MADS-box transcription factor RIN has been widely reported. Here, we describe a bHLH transcription factor, SlbHLH95, whose transcripts accumulated abundantly in breaker+4 and breaker+7 fruits compared with rin (ripening inhibitor) and Nr (never ripe) mutants. Moreover, the promoter activity of SlbHLH95 was regulated by RIN in vivo. Suppression of SlbHLH95 resulted in reduced sensitivity to ethylene, decreased accumulation of total carotenoids, and lowered glutathione content, and inhibited the expression of fruit ripening- and glutathione metabolism-related genes. Conversely, up-regulation of SlbHLH95 in wild-type tomato resulted in higher sensitivity to ethylene, increased accumulation of total carotenoids, slightly premature ripening, and elevated accumulation of glutathione, soluble sugar, and starch. Notably, overexpression of SlbHLH95 in rin led to the up-regulated expression of fruit ripening-related genes (FUL1, FUL2, SAUR69, ERF4, and CNR) and multiple glutathione metabolism-related genes (GSH1, GSH2, GSTF1, and GSTF5). These results clarified that SlbHLH95 participates in the regulation of fruit ripening and affects ethylene sensitivity and multiple metabolisms targeted by RIN in tomato.

Astaxanthin production in a model cyanobacterium Synechocystis sp. PCC 6803.

Heterologous production of a useful carotenoid astaxanthin was achieved in a cyanobacterium Synechocystis sp. PCC 6803 with the aid of marine bacterial genes. Astaxanthin and its intermediates emerged at high levels, whereas β-carotene and zeaxanthin disappeared in the strain. Total carotenoid accumulation was nearly two fold compared with wild type. The astaxanthin-producing strain was capable of only growing heterotrophically, which was likely due to the absence of β-carotene. Further enhanced accumulation was pursued by gene overexpression for possible rate-limiting steps in the biosynthesis pathway.

Banana MaSPL16 Modulates Carotenoid Biosynthesis during Fruit Ripening through Activating the Transcription of Lycopene β-Cyclase Genes.

Carotenoids are a class of bioactive compounds that exhibit health-promoting properties for humans, but their regulation in bananas during fruit ripening remains largely unclear. Here, we found that the total carotenoid content continued to be elevated along the course of banana ripening and peaked at the ripening stage followed by a decrease, which is presumably caused by the transcript abundances of carotenoid biosynthetic genes MaLCYB1.1 and MaLCYB1.2. Moreover, a ripening-inducible transcription factor MaSPL16 was characterized, which was a nuclear protein with transactivation activity. Transient transformation of MaSPL16 in banana fruits led to enhanced transcript levels of MaLCYB1.1 and MaLCYB1.2 and hence the total carotenoid accumulation. Importantly, MaSPL16 stimulated the transcription of MaLCYB1.1 and MaLCYB1.2 through directly binding to their promoters. Collectively, our findings indicate that MaSPL16 behaves as an activator to modulate banana carotenoid biosynthesis, which may provide a new target for molecular improvement of the nutritional and bioactive qualities of agricultural crops that accumulate carotenoids.

Effect of fish steroids 17β-estradiol and 17,20β-dihydroxy-4-pregnen-3-one on growth, accumulation of pigments, and fatty acid profiles in the microalgae Scenedesmus quadricauda (CPCC-158)

The influence of fish steroid hormones on algal (Scenedesmus quadricauda) physiology was investigated, as it is relevant to the use of fishery wastewaters for microalgae biomass production. S. quadricauda was exposed to two steroids, 17β-estradiol (E2) and 17,20,β-dihydroxy-4-pregnen-3-one (17,20β-P), commonly found in fish farm effluents. These hormones demonstrated stimulatory effects on S. quadricauda cell growth and accumulation of chlorophyll-a, total carotenoids, and lipids. Both steroids promoted total carotenoid accumulation to higher degree than they promoted chlorophyll accumulation. E2 was a more powerful inducer of the accumulation of total carotenoids and lipids compared with 17,20β-P. The work was conducted to evaluate the possibility of integrating cold-water fish farming with algae production to maximize nutrient recycling in aquaculture wastewaters. Our data suggest that nano-concentrations of fish sex hormones in aquaculture wastewaters could be used to enhance both algae biomass production and the synthesis of high-value molecules.

INFLUENCE OF FLOODING ON LEAF CELL MEMBRANES OF THREE LATVIAN WHEAT CULTIVARS (TRITICUM AESTIVUM (L)).

Flooding occurs in many wheat-growing regions around the world. During flooding, the gas exchange between soil and air decreases and root hypoxia or anoxia is the major cause of plant growth reduction under this stress. The hypoxia stress triggers stimulate the formation of reactive oxygen species (ROS) and induce oxidative stress in plants. The wheat is one of the most important crops in Latvia and in the world. Although wheat is one of the most intolerant crops to soil flooding. To elucidate the mechanisms involved in soil flooding and the tolerance of three Latvian commercial winter wheat (Triticum aestivum L.) cultivars: ‘Fredis’, ‘Reinis’, ‘Brencis’ and the flooding induced changes in electrolyte leakage, MDA production, and carotenoid production evaluated. The results indicate, that content of MDA, which reflect the level of membrane lipid peroxidation, differ, but no significant decrease of MDA concentration in cultivar ‘Brencis’ caused by increased activity of the antioxidant system. The differences in total carotenoids content in investigated wheat cultivars under simulating natural flooding founded. The most active accumulation of total carotenoids observed in the cultivar ‘Reinis’. The results demonstrate increased electrolyte leakage in cell membranes of the first leaves in all investigated wheat cultivars compared to control. Under flooding, the first leaf of wheat influenced by lower water temperature compared to the first leaf of the control group and that decrease the membrane fluidity, which possibly leads to decreased of membrane permeability. This preliminary data shows that one-week flooding influences to the cell membranes of some Latvian winter wheat cultivars, this influence differs, but cultivar ‘Brencis’ was more tolerant of the flooding.

Accumulation of rosmarinic acid and behaviour of ROS processing systems in Melissa officinalis L. under heat stress

Heat stress (HS) due to increased air temperature is a major agricultural problem. On the other hand, short-term HS can represent a natural easy-to-use elicitor of bioactive compounds in plants. Similar elicitations can be induced by biotechnological approaches such as hydroponic cultures. The present study pioneering investigated the capability of using a short-term HS (38 °C, 5 h) as a tool to rapidly elicit rosmarinic acid (RA) content in leaves of Melissa officinalis L. (a species for which RA is the dominant active phenolic compound) hydroponic cultures, highlighting the cross-talk among antioxidant and signalling molecules involved in the heat acclimation. During HS treatment, we found an elicitation of RA biosynthesis associated with (i) an imbalance in reactive oxygen species (ROS) production and scavenging, (ii) an involvement of reduced ascorbate (AsA) in maintaining a high normal reduced state of cells, (iii) an induction of heat shock proteins (i.e. HSP101-like), and (iv) a stimulation of phytohormones. The RA biosynthesis lasted also during the recovery, although plants activated cellular processes to partially control ROS production, as confirmed by the increased activity of AsA regenerating enzymes, the accumulation of total carotenoids and the stimulation of total antioxidant capacity. The unchanged values of abscisic acid, ethylene and salicylic and jasmonic acids during the recovery phase also documented a reduced demand for protection. The present study represents a wide-ranging investigation of the potential use of HS (without drought interaction) as a technological application for improving bioactive compound production.

The combined influence of 24‑epibrassinolide and 3‑indoleacetic acid on growth and accumulation of pigments and fatty acids in the microalgae Scenedesmus quadricauda (CPCC-158)

Interest in the use of wastewaters of different origins for the industrial production of microalgal biomass for biofuels and bioproducts has stimulated studies on the influence of a variety of compounds in wastewaters on algal physiology. Following the previously published work on the impact of four single phytohormones on the physiology of the microalga Scenedesmus quadricauda (CPCC-158), we investigated the combined effect of the 24‑epibrassinolide (EBL) and 3‑indoleacetic acid (IAA) on S. quadricauda biosynthesis and biomass production. Synergistic increases in S. quadricauda biomass production, chlorophyll-a accumulation, total carotenoid accumulation, as well as total and major neutral lipid (triacylglyceride) accumulation were observed for most of the mixed hormone trials. Mixed hormones had stimulatory effects on growth and biosynthesis of S. quadricauda, but the influence of mixed hormones on algae growth (maximum 1.6-times greater) was less than their influence on algal biosynthesis (maximum 1.7-, 2.7-, and 3.3-fold for chlorophyll-a, total carotenoids, and fatty acids, respectively) compared with single hormone treatments. The mechanism of EBL and IAA cross-talk is likely specific to targeted biosynthetic pathways. The type of relationship between two mixed phytohormones was assessed with Ting-Chao Chou Test. Our results highlight the need for further research on the combined influence of phytohormones on algae physiology.