Effects of Simulated Acid Rain on Photosynthesis in Pinus massoniana and Cunninghamia lanceolata in Terms of Prompt Fluorescence, Delayed Fluorescence, and Modulated Reflection at 820 nm.

The effects of simulated acid rain (SAR) on the photosynthetic performance of subtropical coniferous species have not been thoroughly investigated. In this study, we treated two coniferous species, Pinus massoniana (PM) and Cunninghamia lanceolata (CL), with four gradients of SAR and then analyzed their photosynthetic activities through measurements of gas exchange, prompt fluorescence (PF), delayed fluorescence (DF), and modulated reflection at 820 nm (MR820). Gas exchange analysis indicated that the decrease in the net photosynthetic rate (Pn) in PM and CL was unrelated to stomatal factors. For the PF transients, SAR induced positive K-band and L-band, a significant reduction in photosynthetic performance index (PIABS), the quantum yield of electron transfer per unit cross-section (ETO/CSm), and maximal photochemical efficiency of photosystem II (Fv/Fm). Analysis of the MR820 kinetics showed that the re-reduction kinetics of PSI reaction center (P700+) and plastocyanin (PC+) became slower and occurred at later times under SAR treatment. For the DF signals, a decrease in the amplitude of the DF induction curve reduced the maximum value of DF (I1). These results suggested that SAR obstructed photosystem II (PSII) donor-side and acceptor-side electron transfer capacity, impaired the connectivity between PSII and PSI, and destroyed the oxygen-evolving complex (OEC). However, PM was better able to withstand SAR stress than CL, likely because of the activation of a protective mechanism.

Transcriptome and photosynthetic analyses provide new insight into the molecular mechanisms underlying heat stress tolerance in Rhododendron × pulchrum Sweet.

Rhododendron species provide excellent ornamental use worldwide, yet heat stress (HS) is one of the major threats to their cultivation. However, the intricate mechanisms underlying the photochemical and transcriptional regulations associated with the heat stress response in Rhododendron remain relatively unexplored. In this study, the analyses of morphological characteristics and chlorophyll fluorescence (ChlF) kinetics showed that HS (40 °C/35 °C) had a notable impact on both the donor's and acceptor's sides of photosystem II (PSII), resulting in reduced PSII activity and electron transfer capacity. The gradual recovery of plants observed following a 5-day period of culture under normal conditions indicates the reversible nature of the HS impact on Rhododendron × pulchrum. Analysis of transcriptome data unveiled noteworthy trends: four genes associated with photosynthesis-antenna protein synthesis (LHCb1, LHCb2 and LHCb3) and the antioxidant system (glutamate-cysteine ligase) experienced significant down-regulation in the leaves of R. × pulchrum during HS. Conversely, aseorbate peroxidase and glutathione S-transferase TAU 8 demonstrated an up-regulated pattern. Furthermore, six down-regulated genes (phos-phoenolpyruvate carboxylase 4, sedoheptulose-bisphosphatase, ribose-5-phosphate isomerase 2, high cyclic electron flow 1, beta glucosidase 32 and starch synthase 2) and two up-regulated genes (beta glucosidase 2 and UDP-glucose pyrophosphorylase 2) implicated in photosynthetic carbon fixation and starch/sucrose metabolism were identified during the recovery process. To augment these insights, a weighted gene co-expression network analysis yielded a co-expression network, pinpointing the hub genes correlated with ChlF dynamics' variation trends. The cumulative results showed that HS inhibited the synthesis of photosynthesis-antenna proteins in R. × pulchrum leaves. This disruption subsequently led to diminished photochemical activities in both PSII and PSI, albeit with PSI exhibiting heightened thermostability. Depending on the regulation of the reactive oxygen species scavenging system and heat dissipation, photoprotection sustained the recoverability of R. × pulchrum to HS.

Photosynthetic and physiological responses of different peony cultivars to high temperature.

In order to investigate the causes of the differences in heat tolerance ('Lu He Hong' and 'Zhi Hong'), we studied the physiological changes, photosynthetic properties and regulatory mechanism of the two peony cultivars at high temperature. The results showed that the physiological changed of different peony cultivars varied significantly under high temperature stress. With the extension of high temperature stress time, MDA content of 'Lu He Hong' increased,while 'Zhi Hong' rised first and then decreased, SOD activity of 'Lu He Hong' rised first and then decreased, that of 'Zhi Hong' kept rising, POD activity of 'Lu He Hong' kept decreasing, while 'Zhi Hong' rised. The photosynthetic instrument records the change of peony photosynthesis parameters at high temperature; the chlorophyll A (Chla) fluorescence transient is recorded using the plant efficiency analyzer (PEA), analyzed according to the JIP test (O-J-I-P fluorescence transient analysis), and several parameters were derived to explain the photosynthetic efficiency difference between different peony cultivars. The tested cultivars responded differently to the survey conditions, and the PCA analysis showed that the 'Zhi Hong' was more well tolerated and showed better thermal stability of the PSII. The reduced efficiency of the 'Lu He Hong' PSII antenna leads to higher heat dissipation values to increase the light energy absorbed by unit reaction center (ABS/RC), the energy captured by unit reaction center (TR0/RC), and the energy dissipated by unit reaction center (DI0/RC), which significantly leads to its lower total photosynthetic performance (PItotal). The light capture complex of the variety 'Zhi Hong' has high connectivity with its reaction center, less damage to OEC activity, and better stability of the PSII system. The results show that 'Zhi Hong' improves heat resistance by stabilizing the cell membrane, a strong antioxidant system, as well as a more stable photosynthetic system. The results of this study provide a theoretical basis for the screening of heat-resistant peonies suitable for cultivation in Jiangnan area and for the selection and breeding of heat-resistant cultivars.

Comprehensive Genomic Survey, Structural Classification, and Expression Analysis of WRKY Transcription Factor Family in Rhododendron simsii

(1) Rhododendron is one of the top ten traditional flowers in China, with both high ornamental and economic values. However, with the change of the environment, Rhododendron suffers from various biological stresses. The WRKY transcription factor is a member of the most crucial transcription factor families, which plays an essential regulatory role in a variety of physiological processes and developmental stresses. (2) In this study, 57 RsWRKYs were identified using genome data and found to be randomly distributed on 13 chromosomes. Based on gene structure and phylogenetic relationships, 57 proteins were divided into three groups: I, II, and III. Multiple alignments of RsWRKYs with Arabidopsis thaliana homologous genes revealed that WRKY domains in different groups had different conserved sites. RsWRKYs have a highly conserved domain, WRKYGQK, with three variants, WRKYGKK, WRKYGEK, and WRKYGRK. Furthermore, cis-acting elements analysis revealed that all of the RsWRKYs had stress and plant hormone cis-elements, with figures varying by group. Finally, the expression patterns of nine WRKY genes treated with gibberellin acid (GA), methyl jasmonate (MeJA), heat, and drought in Rhododendron were also measured using quantitative real-time PCR (qRT-PCR). The results showed that the expression levels of the majority of RsWRKY genes changed in response to multiple phytohormones and abiotic stressors. (3) This current study establishes a theoretical basis for future studies on the response of RsWRKY transcription factors to various hormone and abiotic stresses as well as a significant foundation for the breeding of new stress-tolerant Rhododendron varieties.

Characterization, comparative phylogenetic, and gene transfer analyses of organelle genomes of Rhododendron × pulchrum.

Rhododendron × pulchrum, an important horticultural species, is widely distributed in Europe, Asia, and North America. To analyze the phylogenetic and organelle genome information of R. × pulchrum and its related species, the organelle genome of R. × pulchrum was sequenced and assembled. The complete mitochondrial genome showed lineage DNA molecules, which were 816,410 bp long and contained 64 genes, namely 24 transfer RNA (tRNA) genes, 3 ribosomal RNA (rRNA) genes, and 37 protein-coding genes. The chloroplast genome of R. × pulchrum was reassembled and re-annotated; the results were different from those of previous studies. There were 42 and 46 simple sequence repeats (SSR) identified from the mitochondrial and chloroplast genomes of R. × pulchrum, respectively. Five genes (nad1, nad2, nad4, nad7, and rps3) were potentially useful molecular markers. The R. × pulchrum mitochondrial genome collinear alignment among five species of the Ericaceae showed that the mitochondrial genomes of these related species have a high degree of homology with R. × pulchrum in this gene region, and the most conservative genes were trnC-GCA, trnD-GUC, trnM-CAU, trnN-GUU, trnY-GUA, atp4, nad4, nad2, nad5, ccmC, and rrn26. The phylogenetic trees of mitochondrial genome showed that R. simsii was a sister to R. × pulchrum. The results verified that there was gene rearrangement between R. × pulchrum and R. simsii mitochondrial genomes. The codon usage bias of 10 Ericaceae mitochondrial genes and 7 Rhododendron chloroplast genes were influenced by mutation, while other genes codon usages had undergone selection. The study identified 13 homologous fragments containing gene sequences between the chloroplast and mitochondrial genomes of R. × pulchrum. Overall, our results illustrate the organelle genome information could explain the phylogenetics of plants and could be used to develop molecular markers and genetic evolution. Our study will facilitate the study of population genetics and evolution in Rhododendron and other genera in Ericaceae.

Combined de novo transcriptomic and physiological analyses reveal RyALS3-mediated aluminum tolerance in Rhododendron yunnanense Franch.

Rhododendron (Ericaceae) not only has ornamental value, but also has great medicinal and edible values. Many Rhododendron species are native to acid soils where aluminum (Al) toxicity limits plant productivity and species distribution. However, it remains unknown how Rhododendron adapts to acid soils. Here, we investigated the physiological and molecular mechanisms of Al tolerance in Rhododendron yunnanense Franch. We found that the shoots of R. yunnanense Franch did not accumulate Al after exposure of seedlings to 50 µM Al for 7 days but predominantly accumulated in roots, suggesting that root Al immobilization contributes to its high Al tolerance. Whole-genome de novo transcriptome analysis was carried out for R. yunnanense Franch root apex in response to 6 h of 50 µM Al stress. A total of 443,639 unigenes were identified, among which 1,354 and 3,413 were up- and down-regulated, respectively, by 6 h of 50 µM Al treatment. Both Gene Ontology (GO) enrichment and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that genes involved in "ribosome" and "cytoskeleton" are overrepresented. Additionally, we identified Al-tolerance homologous genes including a tonoplast-localized ABC transporter RyALS3; 1. Overexpression of RyALS3; 1 in tobacco plants confers transgenic plants higher Al tolerance. However, root Al content was not different between wild-type plants and transgenic plants, suggesting that RyALS3; 1 is responsible for Al compartmentalization within vacuoles. Taken together, integrative transcriptome, physiological, and molecular analyses revealed that high Al tolerance in R. yunnanense Franch is associated with ALS3; 1-mediated Al immobilization in roots.

Enhanced Salt Tolerance of Torreya grandis Genders Is Related to Nitric Oxide Level and Antioxidant Capacity.

Nitric oxide (NO), a bioactive molecule, is often involved in the regulation of physiological and biochemical processes in stressed plants. However, the effects of NO donors on dioecious plants remain unclear. Using a pot experiment, female and male Torreya grandis were used to study the role of sex and NO in salt stress tolerance. In the present study, female and male T. grandis seedlings pretreated with an NO donor (sodium nitroprusside, SNP) were exposed to salt stress, and then leaf relative water content (RWC), photosynthetic pigments, chlorophyll fluorescence parameters, NO and glutathione levels, oxidative damage, and antioxidant enzyme activities were investigated. Female T. grandis plants had better tolerance to salinity, as they were characterized by significantly higher RWC, pigment content, and photochemical activities of photosystem II (PSII) and fewer negative effects associated with higher nitrate reductase (NR) activity and NO content. Pretreatment with an NO donor further increased the endogenous NO content and NR activity of both female and male T. grandis plants compared with salt treatment. Moreover, pretreatment with an NO donor alleviated salt-induced oxidative damage of T. grandis, especially in male plants, as indicated by reduced lipid peroxidation, through an enhanced antioxidant system, including proline and glutathione accumulation, and increased antioxidant enzyme activities. However, the ameliorating effect of the NO donor was not effective in the presence of the NO scavenger (Nω-nitro-L-arginine methyl ester, L-name). In conclusion, enhanced salt tolerance in T. grandis plants is related to nitric oxide levels and the supply of NO donors is an interesting strategy for alleviating the negative effect of salt on T. grandis. Our data provide new evidence to contribute to the current understanding of NO-induced salt stress tolerance.

Nitric Oxide Improves Salt Tolerance of Cyclocarya paliurus by Regulating Endogenous Glutathione Level and Antioxidant Capacity.

Cyclocarya paliurus is commonly used to treat diabetes in China. However, the natural habitats of C. paliurus are typically affected by salt stress. Previous studies showed that nitric oxide (NO) level was related to salt tolerance of C. paliurus, and its synthesis was induced by exogenous hydrogen sulfide. However, the effects of different NO donors in alleviating the negative effect of salt stress are still unclear. In the present study, C. paliurus seedlings pretreated with three NO donors (S-nitroso-N-acetylpenicillamine, SNAP and S-nitrosoglutathione, GSNO and sodium nitroprusside, SNP) were exposed to salt stress, and then, the total biomass, chlorophyll fluorescence parameters, NO and glutathione levels, oxidative damage, and antioxidant enzyme activities were investigated. The results showed that pretreatment of NO donors maintained chlorophyll fluorescence and attenuated the loss of plant biomass under salt stress, and the best performance was observed in C. paliurus under SNP treatment. We also found that pretreatment of NO donors further increased the endogenous NO content and nitrate reductase (NR) activity compared with salt treatment. Moreover, pretreatment with NO donors, especially SNP, alleviated salt-induced oxidative damage, as indicated by lowered lipid peroxidation, through an enhanced antioxidant system including glutathione accumulation and increased antioxidant enzyme activities. The supply of NO donors is an interesting strategy for alleviating the negative effect of salt on C. paliurus. Our data provide new evidence contributing to the current understanding of NO-induced salt stress tolerance.

The Effect of Anti-browning Agent Activated Carbon and Polyvinyl Pyrrolidone on the Rooting of Embryo Seedlings of "FengDan" and Its Transcriptome Analysis.

Peony is an excellent ornamental, medicinal, and oily plant. Its traditional seed propagation methods have the disadvantages of low propagation coefficient, long seedling cycle, and low seedling emergence rate, which severely restrict the supply of seedlings for the peony industry. Efficient tissue culture technology is an important basis for accelerating its breeding and reproduction, and in vitro seed embryo culturing into seedlings can also effectively avoid the above problems. However, the browning phenomenon caused by man-made damage in the process of seed embryo stripping leads to problems such as low induction rate and difficulty in rooting, and the relationship between anti-browning agents and seed embryo root formation is still unclear. This study intends to improve the induction rate of peony seedlings by using different anti-browning agents and different combinations and to clarify the relationship between anti-browning agents and seedling rooting using transcriptome sequencing methods. The results show that both anti-browning agents, activated carbon (AC) and polyvinyl pyrrolidone (PVP), can increase the germination rate of seed embryos. Testing with 0.9 g/L of AC showed excellent performance of peony rooting rate and seedling growth, but only AC and the combination of AC and PVP can further promote rooting development. Through transcriptome analysis, we found that the AC vs. control check (CK), AC vs. PVP, and PVP vs. AC and PVP groups have significantly more differentially expressed genes than the AC vs. AC and PVP groups. Pathway enrichment analysis shows that "phenylpropanoid biosynthesis"/"cutin, suberin, and wax biosynthesis" is significantly enriched in these groups, while the AC vs. AC and PVP groups are mainly enriched in "cytochrome P450," indicating that AC may promote the further development of roots into seedlings by stimulating "phenylpropanoid biosynthesis" and biosynthesis of stratum cutin and suberin. This study can lay the foundation for understanding the potential molecular mechanism of the anti-browning agent promoting the rooting of seed embryo seedlings and also provide a theoretical basis for perfecting the construction of the peony tissue culture and rapid propagation system.

Multi-nutrient stoichiometry of Chinese hickory (Carya cathayensis) saplings: plant organs vary in their response to nitrogen fertilization.

Nitrogen (N) enrichment from excessive fertilization in managed forests affects biogeochemical cycles on multiple scales, but our knowledge of how N availability shifts multi-nutrient stoichiometries (including macronutrients: N, phosphorus, potassium, calcium, magnesium and micronutrients: manganese, iron and zinc) within and among organs (root, stem and leaf) remains limited. To understand the difference among organs in terms of multi-nutrient stoichiometric homeostasis responding to N fertilization, a six-level N supply experiment was conducted through a hydroponic system to examine stem growth, multi-nutrient concentrations and stoichiometric ratios in roots, stems and leaves of 2-year-old Chinese hickory (Carya cathayensis Sarg.) saplings. Results showed that N supply significantly enhanced leaf length, width, basal diameter and sapling height. Increasing the rates of N also significantly altered multi-nutrient concentrations in roots, stems and leaves. Macronutrients generally respond more positively than micronutrients within organs. Among organs, leaves and stems generally responded more actively to N supply than roots. The stoichiometric ratios of nutrients within different organs changed significantly with N supply, but their direction and degree of change varied by organ. Specifically, increased N supply reduced the ratios of both macronutrients and micronutrients to N in plant organs, while increased N supply elevated the ratios of P to other nutrients. With N fertilization, ratios of micronutrients decreased in leaves and stems and increased in roots. In particular, leaf N and stem Mn stoichiometries responded strongly to N availability, indicating stimulated N uptake but a decreased risk of Mn2+ accumulation to excessive N. Overall, Chinese hickory saplings responded positively to increasing N availability in terms of stem growth, but the multi-nutrient stoichiometric homeostasis was distinctively organ-dependent. These results are expected to enhance our understanding of N-induced changes in homeostasis of multiple nutrients at the organ level and may offer new insights into how plants adapt to increasing N fertilization.

The Complete Chloroplast Genome of Carya cathayensis and Phylogenetic Analysis.

Carya cathayensis, an important economic nut tree, is narrowly endemic to eastern China in the wild. The complete cp genome of C. cathayensis was sequenced with NGS using an Illumina HiSeq2500, analyzed, and compared to its closely related species. The cp genome is 160,825 bp in length with an overall GC content of 36.13%, presenting a quadripartite structure comprising a large single copy (LSC; 90,115 bp), a small single copy (SSC; 18,760 bp), and a pair of inverted repeats (IRs; 25,975 bp). The genome contains 129 genes, including 84 protein-coding genes, 37 tRNA genes, and 8 rRNA genes. A total of 252 simple sequence repeats (SSRs) and 55 long repeats were identified. Gene selective pressure analysis showed that seven genes (rps15, rpoA, rpoB, petD, ccsA, atpI, and ycf1-2) were possibly under positive selection compared with the other Juglandaceae species. Phylogenetic relationships of 46 species inferred that Juglandaceae is monophyletic, and that C. cathayensis is sister to Carya kweichowensis and Carya illinoinensis. The genome comparison revealed that there is a wide variability of the junction sites, and there is higher divergence in the noncoding regions than in coding regions. These results suggest a great potential in phylogenetic research. The newly characterized cp genome of C. cathayensis provides valuable information for further studies of this economically important species.

Integrated transcriptome and amino acid profile analyses reveal novel insights into differential accumulation of theanine in green and yellow tea cultivars.

Tea cultivars with yellow- or white-leaf variations have a high economic value due to their high amino acid (especially theanine) concentration. However, the dynamic changes of amino acid components (especially theanine) and related gene expression during new shoot development in these cultivars are still unclear. In this study, 264 tea samples from four representative varieties picked during the harvest period in spring were analyzed for their amino acid profiles. The dynamic change rules of ethylamine and 19 amino acids were summarized in normal green and yellow cultivars during new shoot development. Interestingly, the theanine concentration in the yellow cultivar was significantly higher than that in the green cultivar, and increased gradually as the leaves matured until they reached a maximum in the one bud and three leaves stage. The amino acid concentration in the leaves of the yellow cultivar increased significantly with leaf position, which was generally in contrast to the normal green cultivar. Transcriptome and correlation analyses revealed that CsGS1, CsPDX2, CsGGP5, CsHEMA3 and CsCLH4 might be the key genes potentially responsible for the differential accumulation of theanine in green and yellow tea cultivars. These results provide further information for the utilization and improvement of tea plants.

Molecular and Photosynthetic Performance in the Yellow Leaf Mutant of Torreya grandis According to Transcriptome Sequencing, Chlorophyll a Fluorescence, and Modulated 820 nm Reflection.

To study the photosynthetic energy mechanism and electron transfer in yellow leaves, transcriptomics combined with physiological approaches was used to explore the mechanism of the yellow leaf mutant Torreya grandis 'Merrillii'. The results showed that chlorophyll content, the maximal photochemical efficiency of PSII (Fv/Fm), and the parameters related to the OJ phase of fluorescence (φEo, φRo) were all decreased significantly in mutant-type T. grandis leaves. The efficiency needed for an electron to be transferred from the reduced carriers between the two photosystems to the end acceptors of the PSI (δRo) and the quantum yield of the energy dissipation (φDo) were higher in the leaves of mutant-type T. grandis compared to those in wild-type leaves. Analysis of the prompt fluorescence kinetics and modulated 820 nm reflection showed that the electron transfer of PSII was decreased, and PSI activity was increased in yellow T. grandis leaves. Transcriptome data showed that the unigenes involved in chlorophyll synthesis and the photosynthetic electron transport complex were downregulated in the leaves of mutant-type T. grandis compared to wild-type leaves, while there were no observable changes in carotenoid content and biosynthesis. These findings suggest that the downregulation of genes involved in chlorophyll synthesis leads to decreased chlorophyll content, resulting in both PSI activity and carotenoids having higher tolerance when acting as photo-protective mechanisms for coping with chlorophyll deficit and decrease in linear electron transport in PSII.

Hypoglycemic Effect of the N-Butanol Fraction of Torreya grandis Leaves on Type 2 Diabetes Mellitus in Rats through the Amelioration of Oxidative Stress and Enhancement of ß-Cell Function.

Materials and Methods: Sprague-Dawley rats were randomly divided into six groups: control, T2DM, metformin, high-dose BFTL (800 mg/kg), middle-dose BFTL (400 mg/kg), and low-dose BFTL (200 mg/kg). After 4 weeks of BFTL treatment, the correlations of serum indicators with protein expression in tissue were determined, and pathological changes in the liver, kidneys, and pancreas were analyzed. Results: Compared with the results in the T2DM group, serum fasting blood glucose, triglyceride, total cholesterol, malondialdehyde, alanine aminotransferase, and aspartate aminotransferase levels were significantly decreased (p < 0.05), whereas superoxide dismutase and glutathione peroxidase levels were significantly increased (p < 0.05) in the high-, middle-, and low-dose BFTL groups. The treatment also improved oral glucose tolerance. In addition, the pathological changes of the liver, kidney, and pancreas were improved by BFTL treatment. Cytochrome and caspase-3 expression in pancreatic was significantly decreased (p < 0.05) by BFTL treatment, whereas the Bcl-2/Bax ratio was significantly increased (p < 0.05). Discussion and Conclusion. BFTL exerted significant hypoglycemic effect on T2DM model rats, and its mechanism involved the suppression of blood glucose levels and oxidative stress by improving the metabolism of blood lipids and antioxidant capacity, boosting ß-cell function, and inhibiting ß-cell apoptosis.

Hydrogen sulfide alleviates salinity stress in Cyclocarya paliurus by maintaining chlorophyll fluorescence and regulating nitric oxide level and antioxidant capacity.

Cyclocarya paliurus is commonly used to treat diabetes in China. However, the natural habitats of C. paliurus are typically affected by salt stress. Hydrogen sulfide (H2S) is a growth regulator that is widely used to enhance plant stress tolerance, but the possible mechanism underlying H2S-alleviated salt stress in C. paliurus remains unclear. C. paliurus seedlings pretreated with NaHS (an H2S donor) were exposed to salt stress, and then, the leaf and total biomass, chlorophyll fluorescence parameters, nitric oxide (NO) content, oxidative damage, and proline and phenolic content were investigated to test the hypothesis that H2S and NO were involved in the salt tolerance of C. paliurus. The results showed that H2S pretreatment maintained chlorophyll fluorescence and attenuated the loss of plant biomass. We also found that H2S pretreatment further increased the endogenous NO content and nitrate reductase activity compared with salt treatment. Moreover, H2S pretreatment alleviated salt-induced oxidative damage, as indicated by lowered lipid peroxidation, through an enhanced antioxidant system including more proline and phenolic accumulation and increased antioxidant enzyme activities. However, C. paliurus leaves treated with the NO scavenger significantly diminished H2S-mediated NO production and alleviation of membrane lipid peroxidation. Thus, we concluded that H2S-induced NO was involved in C. paliurus salt tolerance.

Purified anthocyanins from Zea mays L. cob ameliorates chronic liver injury in mice via modulating of oxidative stress and apoptosis.

BACKGROUND: Purple corn (Zea mays L.) is one of the main economic crops in China and has been used in the treatment of cystitis, urinary infections and obesity. However, purple corncobs, the by-product remaining after processing and having an intense purple-black color, are normally disposed of as waste or used as animal feed. Therefore, to further expand the medicinal value of purple corncob, its content was analyzed and, after purification, the effect and mechanism of purified purple corncob anthocyanins (PPCCA) on CCl4 -induced chronic liver injury in mice were investigated. RESULTS: It was observed that the total anthocyanin content (TAC) from PPCCA (317.51 ± 9.30 mg cyanidin 3-O-glucoside (C-3-G) g-1 dry weight) was significantly higher than that from the purified purple corn seed anthocyanin (266.73 ± 3.67 mg C-3-G g-1 dry weight), of which C-3-G accounted for 90.6% and 90.4% of the TAC, respectively. Furthermore, compared with the CCl4 group, PPCCA treatment significantly reduced liver index, serum total bilirubin, alanine transaminase, aspartate transaminase and liver malondialdehyde levels, but increased liver superoxide dismutase activity. The pathological changes were also improved, such as more regular arrangement of hepatocytes, less swelling, and fewer vacuoles and apoptotic cells. Additionally, mechanistic studies showed that PPCCA downregulated the expression of Caspase-3, Bax and cytochrome P450 2E1 proteins in the liver and upregulated the expression of Bcl-2. CONCLUSION: These results demonstrated that PPCCA could ameliorate CCl4 -induced chronic liver injury by regulating oxidative stress and hepatocyte apoptosis pathways. © 2021 Society of Chemical Industry.

Nitric oxide functions as a signal in ultraviolet-B-induced baicalin accumulation in Scutellaria baicalensis suspension cultures.

Stress induced by ultraviolet-B (UV-B) irradiation stimulates the accumulation of various secondary metabolites in plants. Nitric oxide (NO) serves as an important secondary messenger in UV-B stress-induced signal transduction pathways. NO can be synthesized in plants by either enzymatic catalysis or an inorganic nitrogen pathway. The effects of UV-B irradiation on the production of baicalin and the associated molecular pathways in plant cells are poorly understood. In this study, nitric oxide synthase (NOS) activity, NO release and the generation of baicalin were investigated in cell suspension cultures of Scutellaria baicalensis exposed to UV-B irradiation. UV-B irradiation significantly increased NOS activity, NO release and baicalin biosynthesis in S. baicalensis cells. Additionally, exogenous NO supplied by the NO donor, sodium nitroprusside (SNP), led to a similar increase in the baicalin content as the UV-B treatment. The NOS inhibitor, Nω-nitro-l-arginine (LNNA), and NO scavenger, 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) partially inhibited UV-B-induced NO release and baicalin accumulation. These results suggest that NO is generated by NOS or NOS-like enzymes and plays an important role in baicalin biosynthesis as part of the defense response of S. baicalensis cells to UV-B irradiation.

Cyclic electron flow around photosystem I is required for adaptation to high temperature in a subtropical forest tree, Ficus concinna.

Dissipation mechanisms of excess photon energy under high-temperature stress were studied in a subtropical forest tree seedling, Ficus concinna. Net CO(2) assimilation rate decreased to 16% of the control after 20 d high-temperature stress, and thus the absorption of photon energy exceeded the energy required for CO(2) assimilation. The efficiency of excitation energy capture by open photosystem II (PSII) reaction centres (F(v)'/F(m)') at moderate irradiance, photochemical quenching (q(P)), and the quantum yield of PSII electron transport (Phi(PSII)) were significantly lower after high-temperature stress. Nevertheless, non-photochemical quenching (q(NP)) and energy-dependent quenching (q(E)) were significantly higher under such conditions. The post-irradiation transient of chlorophyll (Chl) fluorescence significantly increased after the turnoff of the actinic light (AL), and this increase was considerably higher in the 39 degrees C-grown seedlings than in the 30 degrees C-grown ones. The increased post-irradiation fluorescence points to enhanced cyclic electron transport around PSI under high growth temperature conditions, thus helping to dissipate excess photon energy non-radiatively.

Antisense inhibition of Rubisco activase increases Rubisco content and alters the proportion of Rubisco activase in stroma and thylakoids in chloroplasts of rice leaves.

BACKGROUND AND AIMS: Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activase (RCA) is a nuclear-encoded chloroplast protein that modifies the conformation of Rubisco, releases inhibitors from active sites, and increases enzymatic activity. It appears to have other functions, e.g. in gibberellin signalling and as a molecular chaperone, which are related to its distribution within the chloroplast. The aim of this research was to resolve uncertainty about the localization of RCA, and to determine whether the distributions of Rubisco and RCA were altered when RCA content was reduced. The monocotyledon, Oryza sativa was used as a model species. METHODS: Gas exchange and Rubisco were measured, and the sub-cellular locations of Rubisco and RCA were determined using immunogold-labelling electron microscopy, in wild-type and antisense rca rice plants. KEY RESULTS: In antisense rca plants, net photosynthetic rate and the initial Rubisco activity decreased much less than RCA content. Immunocytolocalization showed that Rubisco in wild-type and antisense plants was localized in the stroma of chloroplasts. However, the amount of Rubisco in the antisense rca plants was greater than in the wild-type plants. RCA was detected in both the chloroplast stroma and in the thylakoid membranes of wild-type plants. The percentage of RCA labelling in the thylakoid membrane was shown to be substantially decreased, while the fraction in the stroma was increased, by the antisense rca treatment. CONCLUSIONS: From the changes in RCA distribution and alterations in Rubisco activity, RCA in the stroma of the chloroplast probably contributes to the activation of Rubisco, and RCA in thylakoids compensates for the reduction of RCA in the stroma, allowing steady-state photosynthesis to be maintained when RCA is depleted. RCA may also have a second role in protecting membranes against environmental stresses as a chaperone.