BrLETM2 Protein Modulates Anthocyanin Accumulation by Promoting ROS Production in Turnip (Brassica rapa subsp. rapa).

In 'Tsuda' turnip, the swollen root peel accumulates anthocyanin pigments in a light-dependent manner, but the mechanism is unclear. Here, mutant g120w which accumulated extremely low levels of anthocyanin after light exposure was identified. Segregation analysis showed that the anthocyanin-deficient phenotype was controlled by a single recessive gene. By using bulked-segregant analysis sequencing and CAPS marker-based genetic mapping analyses, a 21.6-kb region on chromosome A07 was mapped, in which a calcium-binding EF hand family protein named BrLETM2 was identified as the causal gene. RNA sequencing analysis showed that differentially expressed genes (DEGs) between wild type and g120w in light-exposed swollen root peels were enriched in anthocyanin biosynthetic process and reactive oxygen species (ROS) biosynthetic process GO term. Furthermore, nitroblue tetrazolium (NBT) staining showed that the ROS level decreased in g120w mutant. Anthocyanins induced by UV-A were abolished by the pre-treatment of seedlings with DPI (an inhibitor of nicotinamide adenine nucleoside phosphorylase (NADPH) oxidase) and decreased in g120w mutant. These results indicate that BrLETM2 modulates ROS signaling to promote anthocyanin accumulation in turnip under UV-A and provides new insight into the mechanism of how ROS and light regulate anthocyanin production.

Effects of long light exposure and drought stress on plant growth and glucosinolate production in pak choi (Brassica rapa subsp. chinensis).

Glucosinolates (GLs), found in Brassicaceae family, are precursor metabolites with anti-cancer properties. Increased GLs have been studied under various environmental growth conditions. Pak choi (Brassica rapa subsp. chinensis) is a GL-rich vegetable. We hypothesize that long exposure to light and drought will increase the biomass of, and GL production in, pak choi. The experiment was conducted for 6 weeks. Long light exposure (20 h/day) increased, whilst drought exposure (12 h/week) decreased the plant growth. The plants exposed to a combination of drought and long light conditions showed similar growth pattern as control plants. GL production increased at week 6 in plants exposed to long light, while drought exposure had no impact on GL production, with the exception of glucoraphanin. Significant positive correlations were observed between plant growth and GL yield with accumulated light exposure time. Our findings suggest that long exposure to light can be used to increase both the biomass and GL production in pak choi.

Tunable spectrum resemblance of LED lights for improving the photosynthetic action of Chinese Cabbages.

To increase efficiency, and reduce energy loss and waste, we propose to improve the photosynthetic action spectrum resemblance (SRPAS) of LED light with the absorption spectra of the fresh leaf, for accelerating the growth of Chinese Cabbages. Eight spectral LED lights were adopted to irradiate Chinese Cabbages under 150 µmol•m-2 s-1 for a 16 hd-1 photoperiod. Of these, under the irradiation of blue + broad red + more yellow (BRY2) light with high spectrum resemblance of 75%, the fresh weight and dry weight are 5.1times and 3.0 times, respectively, and the leaf area and leaf number are 1.7 times, as high as under the blue light. The results demonstrate that the optimized LED light can be presumed to have the highest spectrum resemblance (SRPAS) with the absorption spectra of Chinese Cabbages, and the highest energy-conversion efficiency. These conclusions may be of great benefit to further assess and find either an ideal light applied for plant growth or design of better light sources for growing different plants.

Sensitivity difference between skotomorphogenesis and photomorphogenesis of plants to antibiotics: A call for research.

Seedling establishment consists of the former stage (i.e. skotomorphogenesis) and the latter stage (i.e. photomorphogenesis). Due to specific developmental processes in plants, the two stages may have different sensitivities to antibiotics. Tetracycline (TC), for example, is a major-use antibiotic. Radicle length, the relatively sensitive endpoint in plant skotomorphogenesis, is less sensitive than all of the indices of cotyledon colour and pigments in plant photomorphogenesis to TC stress. In conclusion, we suggest that plant photomorphogenesis may be more sensitive than plant skotomorphogenesis to stresses of antibiotics, but which needs further studies.

Light quality-induced changes of carotenoid composition in pak choi Brassica rapa ssp. chinensis.

Carotenoids as part of the photosystems are crucial for their assembly, light-harvesting, and photoprotection. Light of different wavelengths impacts the composition and structure of photosystems, thus offering the possibility to influence the carotenoid concentrations and composition in photosystems by illumination with specific narrow-banded light spectra. Key components involved in the regulation of gene transcription are still poorly characterized, particularly in leafy vegetables as compared to model plants. In particular, the effect of different light qualities and its connection to redox control mechanisms, which also determine the photosystem composition and structure, is not yet well understood. Furthermore, light quality effects are species-dependent, and thus, increase the need to perform research on individual vegetable species such as pak choi Brassica rapa ssp. chinensis. Here, we investigated the carotenoid concentrations and composition of pak choi sprouts grown for 6 days under blue, red, or white light emitting diodes (LEDs) as light source. After 6 days, the total carotenoid content was the highest under white and slightly reduced under blue or red LEDs. Blue, red, and white light differently affected the carotenoid composition mainly due to variations of the ß-carotene content which could be correlated to changes in the transcript levels of ß-carotene hydroxylase 1 (ß-OHASE1). Further investigations implied a redox controlled gene expression of ß-OHASE1. In addition, transcription factors related to light signaling and the circadian clock differed in their transcriptional abundance after exposure to blue and red light. RNA-Seq analysis also revealed increased transcript levels of genes encoding the outer antenna complex of photosystem II under red compared to blue light, indicating an adjustment of the photosystems to the different light qualities which possibly contributed to the alternations in the carotenoid content and composition.

Identification and functional analysis of proteins in response to light intensity, temperature and water potential in Brassica rapa hypocotyl.

Hypocotyl elongation is an early event in plant growth and development and is sensitive to fluctuations in light, temperature, water potential and nutrients. Most research on hypocotyl elongation has focused on the regulatory mechanism of a single environment factor. However, information about combined effects of multi-environment factors remains unavailable, and overlapping sites of the environmental factors signaling pathways in the regulation of hypocotyl elongation remain unclear. To identify how cross-talks among light intensity, temperature and water potential regulate hypocotyl elongation in Brassica rapa L. ssp. chinesis, a comprehensive isobaric tag for relative and absolute quantitation-based proteomic approach was adopted. In total, 7259 proteins were quantified, and 378 differentially expressed proteins (DEPs) were responsive to all three environmental factors. The DEPs were involved in a variety of biochemical processes, including signal transduction, cytoskeletal organization, carbohydrate metabolism, cell wall organization, protein modification and transport. The DEPs did not function in isolation, but acted in a large and complex interaction network to affect hypocotyl elongation. Among the DEPs, phyB was outstanding for its significant fold change in quantity and complex interaction networks with other proteins. In addition, changes of sensitivity to environmental factors in phyB-9 suggested a key role in the regulation of hypocotyl elongation. Overall, the data presented in this study show a profile of proteins interaction network in response to light intensity, temperature and water potential and provides molecular basis of hypocotyl elongation in B. rapa.

Irradiation effects of MeV protons on dry and hydrated Brassica rapa seeds.

Although space radiation is a known risk for space travel and eventual colonization of Moon or Mars, relatively few data exist on radiation effects on potential crop plants. We studied Brassica rapa to assess the tolerance of seeds and seedlings to radiation by exposing dry and hydrated B. rapa seeds to 1, 2 and 3 MeV proton ions of various fluences and examined the effect on germination and root growth. Modeling penetration depth with SRIM code indicated that the applied energy was insufficient to penetrate the seeds; therefore, all energy was deposited into the tissue. Subsequent germination varied based on the incident ion energy and fluence (dose). Dry and hydrated seeds germinate after ion fluence (1013 ions cm-2) irradiation, but the germination percentage decreased with increasing fluence for ions that could penetrate the seed coat (> 1 MeV). Despite their greater volume and mass, hydrated seeds were more sensitive to irradiation than dry seeds. Damage of the seed coat after irradiation led to faster germination and initial seedling growth. Our results suggest that the seed coat represents a valuable natural radiation protection and that low energy protons, the prevailing solar radiation, are suitable for studying radiation effects in seeds and plants.

Transcriptional and translational responses of rapeseed leaves to red and blue lights at the rosette stage.

Under different red (R):blue (B) photon flux ratios, the growth performance of rapeseed (Brassica napus L.) is significantly different. Rapeseed under high R ratios shows shade response, while under high B ratios it shows sun-type morphology. Rapeseed under monochromatic red or blue light is seriously stressed. Transcriptomic and proteomic methods were used to analyze the metabolic pathway change of rapeseed (cv. "Zhongshuang 11") leaves under different R:B photon flux ratios (including 100R:0B%, 75R:25B%, 25R:75B%, and 0R:100B%), based on digital gene expression (DGE) and two-dimensional gel electrophoresis (2-DE). For DGE analysis, 2054 differentially expressed transcripts (|log2(fold change)|≥1, q<0.005) were detected among the treatments. High R ratios (100R:0B% and 75R:25B%) enhanced the expression of cellular structural components, mainly the cell wall and cell membrane. These components participated in plant epidermis development and anatomical structure morphogenesis. This might be related to the shade response induced by red light. High B ratios (25R:75B% and 0R:100B%) promoted the expression of chloroplast-related components, which might be involved in the formation of sun-type chloroplast induced by blue light. For 2-DE analysis, 37 protein spots showed more than a 2-fold difference in expression among the treatments. Monochromatic light (ML; 100R:0B% and 0R:100B%) stimulated accumulation of proteins associated with antioxidation, photosystem II (PSII), DNA and ribosome repairs, while compound light (CL; 75R:25B% and 25R:75B%) accelerated accumulation of proteins associated with carbohydrate, nucleic acid, amino acid, vitamin, and xanthophyll metabolisms. These findings can be useful in understanding the response mechanisms of rapeseed leaves to different R:B photon flux ratios.

Effects of Developmental Stages and Reduced UVB and Low UV Conditions on Plant Secondary Metabolite Profiles in Pak Choi (Brassica rapa subsp. chinensis).

Pak choi (Brassica rapa subsp. chinensis) is rich in secondary metabolites and contains numerous antioxidants, including flavonoids; hydroxycinnamic acids; carotenoids; chlorophylls; and glucosinolates, which can be hydrolyzed to epithionitriles, nitriles, or isothiocyanates. Here, we investigate the effect of reduced exposure to ultraviolet B (UVB) and UV (UVA and UVB) light at four different developmental stages of pak choi. We found that both the plant morphology and secondary metabolite profiles were affected by reduced exposure to UVB and UV, depending on the plant's developmental stage. In detail, mature 15- and 30-leaf plants had higher concentrations of flavonoids, hydroxycinnamic acids, carotenoids, and chlorophylls, whereas sprouts contained high concentrations of glucosinolates and their hydrolysis products. Dry weights and leaf areas increased as a result of reduced UVB and low UV. For the flavonoids and hydroxycinnamic acids in 30-leaf plants, less complex compounds were favored, for example, sinapic acid acylated kaempferol triglycoside instead of the corresponding tetraglycoside. Moreover, also in 30-leaf plants, zeaxanthin, a carotenoid linked to protection during photosynthesis, was increased under low UV conditions. Interestingly, most glucosinolates were not affected by reduced UVB and low UV conditions. However, this study underlines the importance of 4-(methylsulfinyl)butyl glucosinolate in response to UVA and UVB exposure. Further, reduced UVB and low UV conditions resulted in higher concentrations of glucosinolate-derived nitriles. In conclusion, exposure to low doses of UVB and UV from the early to late developmental stages did not result in overall lower concentrations of plant secondary metabolites.

Developmental variation during seed germination and biochemical responses of Brassica rapa exposed to various colored lights.

Light acting as elicitor or stress inducer, it plays a pivotal role in all developmental processes of plant providing necessary building blocks for growth and primary and secondary metabolites production. The main objective of the current study was to investigate the individual effect of colored lights on developmental processes and production of polyphenolics contents in Brassica rapa. In this study, the red and white lights (control) were found to be the most effective sources for seed germination (91%) in Brassica rapa. Similarly, red light enhanced radicle growth (102 mm), while green light suppressed radicle growth (60 mm) as compared to control (67 mm). The red light also promoted the plumule growth (50 mm) as compared to control (37 mm). The maximum biomass gain (67 mg) was observed under red light as compared to control (55 mg). Currently, the maximum total phenolics content (9.49 mg/g-DW) and phenolics production (379.616 mg/L) was observed under the influence of blue lights as compared to control (0.23 mg/g-DW and 8.91 mg/L). Similarly, the blue lights also enhanced the biosynthesis of total flavonoids content (2.2611 mg/g-DW) and flavonoids production (90.44 mg/L) as compared to control (0.0318 md/g-DW and 0.8268 mg/L). The current results represents that red and blue lights are the most effective sources for plantlets development and production of polyphenolics content in Brassica rapa.

Light response of sunflower and canola as affected by plant density, plant genotype and N fertilization.

Crop response to light is an important parameter determining crop growth. Three field (split plots) experiments were conducted to investigate the effects of plant density, plant genotype and N fertilization on the light absorption and light extinction of sunflower (Helianthus annuus L.) and canola (Brassica napus L.). A detailed set of plant growth, light absorption and crop yield and oil related parameters were determined. Light was measured at noon during the sunny days with clear sky. In experiment I, although the plant density (PD) of 14 resulted in the highest rate of sunflower light absorption (31.37%) and light extinction (0.756), the highest rate of grain yield and grain oil yield was resulted at PD12 at 3639 and 1457.9kg/ha, respectively; as well as by genotype SUP.A. In experiment II (canola), PD80 resulted in the highest rate of light absorption (13.13%), light extinction (0.63), grain yield (2189.4kg/ha) and grain oil yield (556.54kg/ha). This was also the case for Genotype H. In experiment III (canola), although N150 resulted in the highest rate of light absorption (10.74%) and light extinction (0.48), the highest rate of grain yield (3413.6kg/ha) and grain oil yield (891.86kg/ha) was resulted at N100 as well as by Genotype H401. Results indicate how light properties, crop growth and yield of sunflower and canola can be affected by plant and environmental parameters, which are also of practical use by farmers.

Identification of Light-Independent Anthocyanin Biosynthesis Mutants Induced by Ethyl Methane Sulfonate in Turnip "Tsuda" (Brassica rapa).

The epidermis of swollen storage roots in purple cultivars of turnip "Tsuda" (Brassica rapa) accumulates anthocyanin in a light-dependent manner, especially in response to UV-A light, of which the mechanism is unclear. In this study, we mutagenized 15,000 seeds by 0.5% (v/v) ethyl methane sulfonate (EMS) and obtained 14 mutants with abnormal anthocyanin production in their epidermis of swollen storage roots. These mutants were classified into two groups: the red mutants with constitutive anthocyanin accumulation in their epidermis of storage roots even in underground parts in darkness and the white mutants without anthocyanin accumulation in the epidermis of storage roots in aboveground parts exposed to sunlight. Test cross analysis demonstrated that w9, w68, w204, r15, r21, r30 and r57 contained different mutations responsible for their phenotypic variations. Further genetic analysis of four target mutants (w9, w68, w204 and r15) indicated that each of them was controlled by a different recessive gene. Intriguingly, the expression profiles of anthocyanin biosynthesis genes, including structural and regulatory genes, coincided with their anthocyanin levels in the epidermis of storage roots in the four target mutants. We proposed that potential genes responsible for the mutations should be upstream factors of the anthocyanin biosynthesis pathway in turnips, which provided resources to further investigate the mechanisms of light-induced anthocyanin accumulation.

Pulsed Light-Emitting Diodes for a Higher Phytochemical Level in Microgreens.

A novel research of pulsed light-emitting diode (LED) lighting versus continuous lighting was conducted by analyzing phytochemical levels in microgreens. Red pak choi (Brassica rapa var. chinensis), mustard (Brassica juncea L.), and tatsoi (Brassica rapa var. rosularis) were grown indoors under HPS lamps supplemented with monochromatic (455, 470, 505, 590, and 627 nm) LEDs [total photosynthetic photon flux density (PPFD) of 200 ± 10 µmol m-2 s-1, for 16 h day-1]. For pulsed light treatments, the frequencies at 2, 32, 256, and 1024 Hz with a duty cycle of 50% monochromatic LEDs were applied. The results were compared to those under the continuous light (0 Hz) condition in terms of total phenolic content, anthocyanins, and antiradical activity (DPPH). The summarized data suggested that pulsed light affected accumulation of secondary metabolites both positive and negative in microgreens. The significant differences in the response of phytochemicals between pulsed light at several frequencies and continuous light were determined. The most positive effects of 2, 256, and 1024 Hz for total phenolic compounds in mustard under all wavelength LEDs were achieved. The LED frequencies at 2 and 32 Hz were the most suitable for accumulation of anthocyanins in red pak choi and tatsoi. The highest antiradical activity under the treatments of 32, 256, and 1024 Hz in mustard and under the 2 Hz frequency in red pak choi and tatsoi was determined.

Reduction of GIGANTEA expression in transgenic Brassica rapa enhances salt tolerance.

KEY MESSAGE: Here we report the enhancement of tolerance to salt stress in Brassica rapa (Chinese cabbage) through the RNAi-mediated reduction of GIGANTEA ( GI ) expression. Circadian clocks integrate environmental signals with internal cues to coordinate diverse physiological outputs. The GIGANTEA (GI) gene was first discovered due to its important contribution to photoperiodic flowering and has since been shown to be a critical component of the plant circadian clock and to contribute to multiple environmental stress responses. We show that the GI gene in Brassica rapa (BrGI) is similar to Arabidopsis GI in terms of both expression pattern and function. BrGI functionally rescued the late-flowering phenotype of the Arabidopsis gi-201 loss-of-function mutant. RNAi-mediated suppression of GI expression in Arabidopsis Col-0 and in the Chinese cabbage, B. rapa DH03, increased tolerance to salt stress. Our results demonstrate that the molecular functions of GI described in Arabidopsis are conserved in B. rapa and suggest that manipulation of gene expression through RNAi and transgenic overexpression could enhance tolerance to abiotic stresses and thus improve agricultural crop production.

Exploring miRNAs involved in blue/UV-A light response in Brassica rapa reveals special regulatory mode during seedling development.

BACKGROUND: Growth, development, and pigment synthesis in Brassica rapa subsp. rapa cv. Tsuda, a popular vegetable crop, are influenced by light. Although microRNAs (miRNAs) have vital roles in the metabolic processes and abiotic stress responses of plants, whether miRNAs play a role in anthocyanin biosynthesis and development of Tsuda seedlings exposed to light is unknown. RESULTS: Seventeen conserved and 226 novel miRNAs differed at least 2-fold in response to blue and UV-A light compared with levels after a dark treatment. Real time PCR showed that BrmiR159, BrmiRC0191, BrmiRC0460, BrmiRC0323, BrmiRC0418, BrmiRC0005 were blue light-induced and northern blot revealed that the transcription level of BrmiR167 did not differ significantly among seedlings treated with dark, blue or UV-light. BrmiR156 and BrmiR157 were present in the greatest amount (number of reads) and among their 8 putative targets in the SPL gene family, only SPL9 (Bra004674) and SPL15 (Bra003305) increased in expression after blue or UV-A exposure. In addition, miR157-guided cleavage of target SPL9 mRNAs (Bra004674, Bra016891) and SPL15 mRNAs (Bra003305, Bra014599) took place 10 or 11 bases from the 5' ends of the binding region in the miR157 sequence. CONCLUSIONS: A set of miRNAs and their targets involved in the regulation of the light-induced photomorphogenic phenotype in seedlings of Brassica rapa was identified, providing new insights into blue and UV-A light-responsive miRNAs in seedlings of Tsuda and evidence of multiple targets for the miRNAs and their diverse roles in plant development.

Selection during crop diversification involves correlated evolution of the circadian clock and ecophysiological traits in Brassica rapa.

Crop selection often leads to dramatic morphological diversification, in which allocation to the harvestable component increases. Shifts in allocation are predicted to impact (as well as rely on) physiological traits; yet, little is known about the evolution of gas exchange and related anatomical features during crop diversification. In Brassica rapa, we tested for physiological differentiation among three crop morphotypes (leaf, turnip, and oilseed) and for correlated evolution of circadian, gas exchange, and phenological traits. We also examined internal and surficial leaf anatomical features and biochemical limits to photosynthesis. Crop types differed in gas exchange; oilseed varieties had higher net carbon assimilation and stomatal conductance relative to vegetable types. Phylogenetically independent contrasts indicated correlated evolution between circadian traits and both gas exchange and biomass accumulation; shifts to shorter circadian period (closer to 24 h) between phylogenetic nodes are associated with higher stomatal conductance, lower photosynthetic rate (when CO2 supply is factored out), and lower biomass accumulation. Crop type differences in gas exchange are also associated with stomatal density, epidermal thickness, numbers of palisade layers, and biochemical limits to photosynthesis. Brassica crop diversification involves correlated evolution of circadian and physiological traits, which is potentially relevant to understanding mechanistic targets for crop improvement.

Effect of microwave treatment on the efficacy of expeller pressing of Brassica napus rapeseed and Brassica juncea mustard seeds.

A study was conducted to evaluate the effect of microwave heating on the efficacy of expeller pressing of rapeseed and mustard seed and the composition of expeller meals in two types of Brassica napus rapeseed (intermediate- and low-glucosinolate) and in Brassica juncea mustard (high-glucosinolate). Following microwave treatment, the microstructure of rapeseed using transmission electron microscopy showed a significant disappearance of oil bodies and myrosin cells. After 6 min of microwave heating (400 g, 800 W), the oil content of rapeseed expeller meal decreased from 44.9 to 13.5% for intermediate-glucosinolate B. napus rapeseed, from 42.6 to 11.3% for low-glucosinolate B. napus rapeseed, and from 44.4 to 14.1% for B. juncea mustard. The latter values were much lower than the oil contents of the corresponding expeller meals derived from the unheated seeds (i.e., 26.6, 22.6, and 29.8%, respectively). Neutral detergent fiber (NDF) contents showed no differences except for the expeller meal from the intermediate-glucosinolate B. napus rapeseed, which increased from 22.7 to 29.2% after 6 min of microwave heating. Microwave treatment for 4 and 5 min effectively inactivated myrosinase enzyme of intermediate-glucosinolate B. napus rapeseed and B. juncea mustard seed, respectively. In low-glucosinolate B. napus rapeseed the enzyme appeared to be more heat stable, with some activity being present after 6 min of microwave heating. Myrosinase enzyme inactivation had a profound effect on the glucosinolate content of expeller meals and prevented their hydrolysis to toxic breakdown products during the expelling process. It appeared evident from this study that microwave heating for 6 min was an effective method of producing expeller meal without toxic glucosinolate breakdown products while at the same time facilitating high yield of oil during the expelling process.

Using a non-invasive technique in nutrition: synchrotron radiation infrared microspectroscopy spectroscopic characterization of oil seeds treated with different processing conditions on molecular spectral factors influencing nutrient delivery.

Non-invasive techniques are a key to study nutrition and structure interaction. Fourier transform infrared microspectroscopy coupled with a synchrotron radiation source (SR-IMS) is a rapid, non-invasive, and non-destructive bioanalytical technique. To understand internal structure changes in relation to nutrient availability in oil seed processing is vital to find optimal processing conditions. The objective of this study was to use a synchrotron-based bioanalytical technique SR-IMS as a non-invasive and non-destructive tool to study the effects of heat-processing methods and oil seed canola type on modeled protein structure based on spectral data within intact tissue that were randomly selected and quantify the relationship between the modeled protein structure and protein nutrient supply to ruminants. The results showed that the moisture heat-related processing significantly changed (p<0.05) modeled protein structures compared to the raw canola (control) and those processing by dry heating. The moisture heating increased (p<0.05) spectral intensities of amide I, amide II, α-helices, and ß-sheets but decreased (p<0.05) the ratio of modeled α-helices to ß-sheet spectral intensity. There was no difference (p>0.05) in the protein spectral profile between the raw and dry-heated canola tissue and between yellow- and brown-type canola tissue. The results indicated that different heat processing methods have different impacts on the protein inherent structure. The protein intrinsic structure in canola seed tissue was more sensitive and more response to the moisture heating in comparison to the dry heating. These changes are expected to be related to the nutritive value. However, the current study is based on limited samples, and more large-scale studies are needed to confirm our findings.

Influence of microwaves treatment of rapeseed on phenolic compounds and canolol content.

Rapeseeds were treated with microwaves under 800 W for 0, 1, 2, 3, 4, 5, 6, 7, and 8 min at a frequency of 2450 MHz, and oil was extracted with a press to investigate the influence on phenolic compounds, including sinapine, the main free phenolic acids, and canolol content in the rapeseeds and oil from them. The results indicated that sinapine and sinapic acid was the main phenolic compound and free phenolic acid in the rapeseed, respectively, and canolol was the main phenolic compound in the oil from rapeseed by cold press. Microwave treatment significantly influenced phenolic compounds content in the rapeseeds and oil from them. The sinapine, sinapic acid, and canolol content in rapeseed first increased and then decreased depending on the period of microwave radiation (p < 0.05). The canolol content of 7 min microwave pretreatment rapeseed increased to the maximum and was approximately six times greater than that of the unroasted rapeseed. The amount of canolol formed was significantly correlated with the content of sinapic acid and sinapine (for sinapic acid, r = -0.950, p < 0.001, for sinapine, r = -0.828, p < 0.05) and also the loss of sinapic acid and sinapine (for sinapic acid, r = 0.997, p < 0.001, for sinapine, r = 0.952, p < 0.05) during roasting. There were differences in the transfer rate of difference phenolic compounds to the oil extracted by press. Almost all of the sinapine remained in the cold-pressed cake and only 1.4-2.7% of the sinapic acid, whereas approximately 56-83% of the canolol was transferred to the oil. The transfer ratio of canolol significantly increased with microwave radiation time (p < 0.001). Microwave pretreatment of rapeseed benefited improving the oxidative stability of oil.

Chalcone synthase family genes have redundant roles in anthocyanin biosynthesis and in response to blue/UV-A light in turnip (Brassica rapa; Brassicaceae).

PREMISE OF THE STUDY: The epidermis of Brassica rapa (turnip) cv. Tsuda contains light-induced anthocyanins, visible signs of activity of chalcone synthase (CHS), a key anthocyanin biosynthetic enzyme, which is encoded by the CHS gene family. To elucidate the regulation of this light-induced pigmentation, we isolated Brassica rapa CHS1-CHS6 (BrCHS1-CHS6) and characterized their cis-elements and expression patterns. METHODS: Epidermises of light-exposed swollen hypocotyls (ESHS) were harvested to analyze transcription levels of BrCHS genes by real-time PCR. Different promoters for the genes were inserted into tobacco to examine pCHS-GUS activity by histochemistry. Yeast-one-hybridization was used to detect binding activity of BrCHS motifs to transcription factors. KEY RESULTS: Transcript levels of BrCHS1, -4, and -5 and anthocyanin-biosynthesis-related genes F3H, DFR, and ANS were high, while those of BrCHS2, -3, and -6 were almost undetectable in pigmented ESHS. However, in leaves, CHS5, F3H, and ANS expression was higher than in nonpigmented ESHS, but transcription of DFR was not detected. In the analysis of BrCHS1 and BrCHS3 promoter activity, GUS activity was strong in pigmented flowers of BrPCHS1-GUS-transformed tobacco plants, but nearly absent in BrPCHS3-GUS-transformed plants. Transcript levels of regulators, BrMYB75 and BrTT8, were strongly associated with the anthocyanin content and were light-induced. Coregulated cis-elements were found in promoters of BrCHS1,-4, and -5, and BrMYB75 and BrTT8 had high binding activities to the BrCHS Unit 1 motif. CONCLUSIONS: The chalcone synthase gene family encodes a redundant set of light-responsive, tissue-specific genes that are expressed at different levels and are involved in flavonoid biosynthesis in Tsuda turnip.