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Dihydrotanshinone I (DHT), a bioactive compound in Salvia miltiorrhiza, was reported to exhibit cytotoxicity against various malignancies. However, the underlying mechanism on ovarian cancer remains unclear. Here, DHT inhibited cell viability of ovarian cancer HO8910PM, SKOV3, A2780 and ES2 cells. It showed moderate inhibitory effect on ovarian epithelial IOSE80 cells and lower toxicity than chemotherapy drugs. DHT induced apoptosis and G2 cell cycle arrest accompanied by reduced expression of Bcl-2, Caspase-3, and increased Bax. Meanwhile, DHT increased ROS accumulation, decreased mitochondrial membrane potential and activated oxidative stress in HO8910PM and ES2 cells. Mechanistically, DHT inhibited Nrf2 and p62 expression, Nrf2 target genes and enzymes, and Nrf2 nuclear translocation, while increased the expression of Nrf2 inhibitor Keap1. NAC, a ROS scavenger, rescued DHT-induced proliferation inhibition, ROS generation and Nrf2 inhibition. DHT alleviated tBHQ-induced Nrf2 expression and increased its mRNA level. However, the proteasome inhibitor MG132 blocked DHT-induced Nrf2 inhibition, suggesting a post-translational regulation manner. DHT enhanced Nrf2 binding with Keap1, leading to potentiated Nrf2 ubiquitination degradation. Furthermore, Nrf2 and p62 overexpression blocked DHT-induced Nrf2 and p62 inhibition. Consistent with the in vitro results, DHT significantly delayed tumor growth in HO8910PM and ES2 xenograft nude mice, decreased tumor marker HE4 and CA125 levels, reversed the abnormally expressed proteins including Ki67, Nrf2, p62, Keap1, Bcl-2, CyclinB1, Cdc-2, and antioxidant enzymes SOD, CAT in vivo. Serum from DHT-treated mice also inhibited cell growth in vitro. Taken together, DHT exhibits anti-ovarian tumor effect by activating oxidative stress through ubiquitination-mediated Nrf2 degradation. Our findings implicate a potential application of DHT for ovarian cancer therapy.

The dried root of Tetrastigma hemsleyanum Diels et Gilg is used as a traditional Chinese medicine in southern China, as a folk remedy for carcinomas and gastrointestinal diseases. The total flavonoids of T. hemsleyanum (THTF) provide its main bioactive constituents. However, the mechanisms underlying its potential activity on colorectal cancer are still unknown. Here, we investigated the antitumor effect of THTF on colorectal cancer in vitro and in vivo. It was found that THTF inhibited HCT-116 and HT-29 cell growth, with an IC

Tetrastigma hemsleyanum Diels et Gilg is a dietary supplement in southern China. The total flavonoids of T. hemsleyanum (THTF) can be used for gastrointestinal disease treatment. Colorectal cancer (CRC) is associated with gut microbiota dysbiosis. This study was designed to investigate the effect of THTF on CRC from gut microbiota and fecal metabolomics. THTF (120 mg/kg) oral gavage reduced tumor growth and protected intestinal function (p-p65/p65, ZO-1) in HCT116 xenografts. THTF increased probiotics Bifidobacteriales, Bifidobacteriaceae, Bifidobacterium, Bifidobacterium pseudolongum, and decreased "harmful" bacteria Bacteroidota, Firmicutes, Bacteroidia, Rikenellaceae, Odoribacter, Alistipes richness. Furthermore, THTF restored abnormal fecal metabolite levels. It showed a strong correlation among gut microbiota, metabolites, and tumor weight. Finally, THTF promoted Bifidobacterium pseudolongum growth in vitro, whose cell-free supernatant further inhibited HCT116 cell proliferation and clonogenicity. Together, THTF delays CRC tumor growth by maintaining microbiota homeostasis, restoring fecal metabolites, and protecting intestinal function.

A catalytic asymmetric [3 + 3] annulation of aziridines with substituted 2-vinylindoles was developed. The reaction proceeds through copper-catalyzed ring-opening of aziridines followed by base-promoted intramolecular aza-Michael addition in a one-pot process. This strategy provides an efficient method for the direct synthesis of 1,4-disubstituted tetrahydro-β-carbolines with generally high diastereo- and enantioselectivities (up to >20 : 1 dr, 96% ee).

Background Meiosis of newly formed allopolyploids frequently encounter perturbations induced by the merging of divergent and hybridizable genomes. However, to date, the meiotic properties of allopolyploids with dysploid parental karyotypes have not been studied in detail. The allotetraploid Cucumis ×hytivus (HHCC, 2n = 38) was obtained from interspecific hybridization between C. sativus (CC, 2n = 14) and C. hystrix (HH, 2n = 24) followed by chromosome doubling. The results of this study thus offer an excellent opportunity to explore the meiotic properties of allopolyploids with dysploid parental karyotypes. Results In this report, we describe the meiotic properties of five chromosomes (C5, C7, H1, H9 and H10) and two genomes in interspecific hybrids and C. ×hytivus (the 4th and 14th inbred family) through oligo-painting and genomic in situ hybridization (GISH). We show that 1) only two translocations carrying C5-oligo signals were detected on the chromosomes C2 and C4 of one 14th individual by the karyotyping of eight 4th and 36 14th plants based on C5- and C7-oligo painting, and possible cytological evidence was observed in meiosis of the 4th generation; 2) individual chromosome have biases for homoeologous pairing and univalent formation in F1 hybrids and allotetraploids; 3) extensive H-chromosome autosyndetic pairings (e.g., H-H, 25.5% PMCs) were observed in interspecific F1 hybrid, whereas no C-chromosome autosyndetic pairings were observed (e.g. C-C); 4) the meiotic properties of two subgenomes have significant biases in allotetraploids: H-subgenome exhibits higher univalent and chromosome lagging frequencies than C-subgenome; and 5) increased meiotic stability in the S14 generation compared with the S4 generation, including synchronous meiosis behavior, reduced incidents of univalent and chromosome lagging. Conclusions These results suggest that the meiotic behavior of two subgenomes has dramatic biases in response to interspecific hybridization and allopolyploidization, and the meiotic behavior harmony of subgenomes is a key subject of meiosis evolution in C. ×hytivus. This study helps to elucidate the meiotic properties and evolution of nascent allopolyploids with the dysploid parental karyotypes.

How to efficiently utilize visible light and highly separate photo-induced charges is now a hot topic in the field of photocatalysis. Herein, various amounts (1–5%, wt%) of Ag nanoparticles were selectively deposited on the surface of the polar material Na3VO2B6O11 (NVB) via the method of photoreduction. Due to the presence of external screening effect, the Ag nanoparticles were selectively deposited on the positive domains of NVB materials. Through DFT, the (110) facet with excessive electrons accumulated has a high reduction ability to deposit the Ag nanoparticles on the edge of NVB crystals. It was also found that the surface plasmon resonances effect of Ag nanoparticles led to the absorption spectrum of NVB broadened to the visible range around 400–800 nm. Under visible light irradiation, the photodegradation efficiency of NVB was significantly enhanced with the 4% Ag deposition, which reached 96% for 2-Chlorophenol (2-CP) degradation in 100 min. It indicates that the screening effect of NVB combination with the surface plasmon resonances effect from Ag nanoparticles can provide a synergistic effect on the enhanced photocatalytic activity during the 2-CP degradation.

Efficient charge separation and suitable band alignment are critical for developing excellent photocatalysts. Boron–oxygen-based materials have been proven to be significant semiconductor photocatalysts to solve the energy crisis. Our results suggested that the separation of photogenerated carriers can be promoted by tuning the band gap of the materials from indirect to direct by the substitution of cations. Almost 87.8% and 71.5% of the total chloride contents were converted to Cl− anions after 20 minutes of UV-Vis light illumination for the indirect-band-gap material KBBO and the direct-band-gap material NBBO for 2,4-DCP degradation, respectively. The dechlorination efficiency of KBBO was approximately 5.3 times that of the commercial P25 TiO2 catalyst. The increased activity could be ascribed to the different locations of the photoinduced charges, making the charges have a long-term effect on the contaminants. By the KPFM method, we concluded that the materials with larger surface potential changes would behave higher photocatalytic activity. This contribution can provide a new approach to optimize the boron–oxygen-based materials for designing efficient photocatalysts.

The contamination of chlorophenols in water has been considered as an urgent environmental issue. In this study, two polar photocatalysts with a similar structure, K3B6O10Br (KBB) and K3B6O10Cl (KBC) were synthesized through a high temperature solid phase method and applied for the effective mineralization and removal of the chlorophenols. More than 92.0% of 2-chlorophenols can be fully degraded within 16 min under UV light irradiation, which is six times faster than the commercial P25 TiO2 catalyst. The out-of-center distortions capability of the XK6 octahedrons is greatly influenced by X (X = Cl and Br) atoms. The magnitude of the out-of-center distortion of KBC and KBB were 0.137 and 0.027, respectively. A better photocatalytic activity performance was therefore observed for KBC due to its higher spontaneous polarization ability and facile charge separation process. Kelvin probe force microscopy (KPFM) experiments further proved KBC has a larger surface potential change before and after the light irradiation. Reactive species capture experiments confirmed the role of radicals in the order of ˙O2− > e− > h+ > ˙OH.

Allopolyploids undergo “genomic shock” leading to significant genetic and epigenetic modifications. Previous studies have mainly focused on nuclear changes, while little is known about the inheritance and changes of organelle genome in allopolyploidization. The synthetic allotetraploid Cucumis ×hytivus, which is generated via hybridization between C. hystrix and C. sativus, is a useful model system for studying cytonuclear variation. Here, we report the chloroplast genome of allotetraploid C. ×hytivus and its diploid parents via sequencing and comparative analysis. The size of the obtained chloroplast genomes ranged from 154 673 to 155 760 bp, while their gene contents, gene orders, and GC contents were similar to each other. Comparative genome analysis supports chloroplast maternal inheritance. However, we identified 51 indels and 292 SNP genetic variants in the chloroplast genome of the allopolyploid C. ×hytivus relative to its female parent C. hystrix. Nine intergenic regions with rich variation were identified through comparative analysis of the chloroplast genomes within the subgenus Cucumis. The phylogenetic network based on the chloroplast genome sequences clarified the evolution and taxonomic position of the synthetic allotetraploid C. ×hytivus. The results of this study provide us with an insight into the changes of organelle genome after allopolyploidization, and a new understanding of the cytonuclear evolution.

Studies have shown that polyploidy has pronounced effects on plants in multiple aspects, including genome structure, gene expression, metabolism and so on, which finally induce changes in phenotype. Many of these changes occurred immediately after polyploidization and retained or lost later. Therefore, it is meaningful for crop breeders to gain knowledge of these changes when it is relatively stable. In this study, we investigated the phenotypes of a highly self-pollinated synthesized allotetraploid in Cucumis, named with Cucumis × hytivus J. F. Chen & J. H. Kirkbr. (C. ×hytivus for short). Results showed that although many phenotypes of C. ×hytivus were intermediate between its parents, total leaf area and cell size exhibited parent-of-origin and dosage effect, respectively. Additionally, C. ×hytivus exhibited divergent biomass allocation strategy compared to the parents, developing more leaves. Beside the commonalities across different polyploid systems, the combination of hybridity and genome duplication in allopolyploids may lead to a diverse possibility of phenotypic changes. In spite of the reduced light absorption by less photosynthetic pigments in young leaves, allopolyploidy caused limited adverse effect on the photosynthesis of C. ×hytivus, which may benefit from the increased leaf thickness and potentially facilitated the survival and speciation of this novel species. The present study offers novel insights into the varied phenotypic effects of polyploidy and is a valuable reference for the crop improvement through polyploidization.

The importance of allopolyploidy in plant evolution has been widely recognized. The genetic changes triggered by allopolyploidy, however, are not yet fully understood due to inconsistent phenomena reported across diverse species. The construction of synthetic polyploids offers a controlled approach to systematically reveal genomic changes that occur during the process of polyploidy. This study reports the first fully sequenced synthetic allopolyploid constructed from a cross between Cucumis sativus and C. hystrix, with high‐quality assembly. The two subgenomes are confidently partitioned and the C. sativus‐originated subgenome predominates over the C. hystrix‐originated subgenome, retaining more sequences and showing higher homeologous gene expression. Most of the genomic changes emerge immediately after interspecific hybridization. Analysis of a series of genome sequences from several generations (S0, S4–S13) of C. ×hytivus confirms that genomic changes occurred in the very first generations, subsequently slowing down as the process of diploidization is initiated. The duplicated genome of the allopolyploid with double genes from both parents broadens the genetic base of C. ×hytivus, resulting in enhanced phenotypic plasticity. This study provides novel insights into plant polyploid genome evolution and demonstrates a promising strategy for the development of a wide array of novel plant species and varieties through artificial polyploidization., The first whole‐genome sequence of a synthetic allopolyploid in Cucumis demonstrates significant subgenome dominance. Comparative genomic analyses on interspecific hybrid and different generations of allopolyploids successfully differentiate the divergent roles of hybridization, genome duplication, and diploidization in shaping the genome. Moreover, the merger of two distinct genomes practically creates a novel allopolyploid species with higher fitness.

Long non-coding RNAs (lncRNAs) play critical regulatory roles in various biological processes. However, the presence of lncRNAs and how they function in plant polyploidy are still largely unknown. Hence, we examined the profile of lncRNAs in a nascent allotetraploid Cucumis hytivus (S14), its diploid parents, and the F1 hybrid, to reveal the function of lncRNAs in plant-interspecific hybridization and whole genome duplication. Results showed that 2206 lncRNAs evenly transcribed from all 19 chromosomes were identified in C. hytivus, 44.6% of which were from intergenic regions. Based on the expression trend in allopolyploidization, we found that a high proportion of lncRNAs (94.6%) showed up-regulated expression to varying degrees following hybridization. However, few lncRNAs (33, 2.1%) were non-additively expressed after genome duplication, suggesting the significant effect of hybridization on lncRNAs, rather than genome duplication. Furthermore, 253 cis-regulated target genes were predicted for these differentially expressed lncRNAs in S14, which mainly participated in chloroplast biological regulation (e.g., chlorophyll synthesis and light harvesting system). Overall, this study provides new insight into the function of lncRNAs during the processes of hybridization and polyploidization in plant evolution.

The effective spatial separation and migration of photo-induced electron-hole pairs to surface active sites is a challenging topic in the field of photocatalysis. Rational design and precise control over charge carriers’ transportation in polar materials with built-in electric field are favorable for achieving its optimal photocatalytic performance. By deposition of Au nanoparticles (Au NPs) and high valence metal oxides PbO2 onto different face of borate-based polar Na3VO2B6O11 (NVB) material, the transfer behavior of the photo charges was systemically studied. It was found that under light irradiation, the electrons were transferred to (0 2 0) plane and the holes were aggregated on (2 0 0) plane of the crystal, respectively. The Au-NVB samples shown the best photocatalytic activity, finishing the reaction in just 20 min and 100 min for the degradation of 2-chlorophenol and tetracycline pollutants, respectively, which is 1.2 times that of pure NVB. This discovery complements the understanding of spatial separation of photo-induced charges in borate based polar materials and provides great potential for further application of such materials.

Autophagy is well-known as a conserved survival mechanism that protects cells from adverse environments, and autophagy-related protein 8 (ATG8) plays a key role in autophagy process as an essential component. However, the contribution of ATG8 to plant tolerance to environmental stresses is ambiguous. To gain insight into whether and how ATG8 gene functions in plant adaptation to adverse environment conditions, we characterized an ATG8 gene CaATG8c from pepper (Capsicum annuum L.), and found that the deduced amino acid sequence of CaATG8c gene contained the conserved necessary domains and residue for ATG8 functions. Under normal condition, the expression of CaATG8c was detected in all pepper tissues/organs, and its subcellular expression was located to the cytoplasm in onion epidermal cells. The silencing-expression of CaATG8c rendered pepper seedlings more sensitive to heat and salt stress by aggravating the chlorophyll degradation, MDA accumulation and SOD activity decrease. Unexpectedly, the over-expression of CaATG8c gene also reduced Arabidopsis tolerance to heat and salt stress by inhibiting the growth of primary roots and the generation of secondary roots, and disturbing the expression of stress response genes. Our results suggested that both silencing- and over-expression of CaATG8c gene conferred plants more sensitivity to heat and salt stress. Furthermore, the possible mechanism for CaATG8c silencing is speculated to the reduced ability to remove accumulated ROS, whereas for gene over-expression, it is supposed to the disturbance of ROS signal. We propose that the stable and timely expression of CaATG8c may be important for plant adaption to adverse environments.

Hsp70s function as molecular chaperones and are encoded by a multi-gene family whose members play a crucial role in plant response to stress conditions, and in plant growth and development. Pepper (Capsicum annuum L.) is an important vegetable crop whose genome has been sequenced. Nonetheless, no overall analysis of the Hsp70 gene family is reported in this crop plant to date. To assess the functionality of Capsicum annuum Hsp70 (CaHsp70) genes, pepper genome database was analyzed in this research. A total of 21 CaHsp70 genes were identified and their characteristics were also described. The promoter and transcript expression analysis revealed that CaHsp70s were involved in pepper growth and development, and heat stress response. Ectopic expression of a cytosolic gene, CaHsp70-2, regulated expression of stress-related genes and conferred increased thermotolerance in transgenic Arabidopsis. Taken together, our results provide the basis for further studied to dissect CaHsp70s' function in response to heat stress as well as other environmental stresses.

Allopolyploids are often faced with the challenge of maintaining well-coordination between nuclear and cytoplasmic genes inherited from different species. The synthetic allotetraploid Cucumis × hytivus is a useful model to explore cytonuclear coevolution. In this study, the sequences and expression of cytonuclear enzyme complex RuBisCO as well as its content and activity in C. × hytivus were compared to its parents to explore plastid–nuclear coevolution. The plastome-coded rbcL gene sequence was confirmed to be stable maternal inheritance, and parental copy of nuclear rbcS genes were both preserved in C. × hytivus. Thus, the maternal plastid may interact with the biparentally inherited rbcS alleles. The expression of the rbcS gene of C-homoeologs (paternal) was significantly higher than that of H-homoeologs (maternal) in C. × hytivus (HHCC). Protein interaction prediction analysis showed that the rbcL protein has stronger binding affinity to the paternal copy of rbcS protein than that of maternal copy in C. × hytivus, which might explain the transcriptional bias of the rbcS homoeologs. Moreover, both the activity and content of RuBisCO in C. × hytivus showed mid-parent heterosis. In summary, our results indicate a paternal transcriptional bias of the rbcS genes in C. × hytivus, and we found new nuclear–cytoplasmic combination may be one of the reasons for allopolyploids heterosis.

Heat stress has become a major threat to crop production due to global warming; however, the mechanisms underlying plant high-temperature sensing are not well known. In plants, the membrane-anchored receptor-like kinases (RLKs) relay environmental signals into the cytoplasm. In a previous study, we isolated a wall-associated RLK-like (WAKL) gene CaWAKL20 from pepper (Capsicum annuum L.). Here, the amino acid sequence of CaWAKL20 was characterized and found to consist of conserved domains of WAK/WAKL family, including an extracellular region containing a GUB-WAK binding domain and a degenerated EGF2-like domain; a transmembrane region; and an intercellular region with an STKc catalytic domain. Moreover, CaWAKL20 transcription was inhibited by heat stress, whereas it was induced by both ABA and H2O2 treatments. Silencing of CaWAKL20 enhanced pepper thermotolerance, while overexpression decreased Arabidopsis thermotolerance. Additionally, Arabidopsis lines overexpressing CaWAKL20 showed less sensitivity to ABA during seed germination and root growth. Finally, the survival rate of Arabidopsis seedlings under heat stress treatment was enhanced by ABA pre-treatment, while it was compromised by the overexpression of CaWAKL20. Furthermore, the heat-induced expression of several ABA-responsive genes and some key regulator genes for thermotolerance was decreased in Arabidopsis CaWAKL20-overexpression lines. These results suggest that CaWAKL20 negatively modulates plant thermotolerance by reducing the expression of ABA-responsive genes, laying a foundation for further investigation into the functional mechanisms of WAKs/WAKLs in plants undergoing environmental stresses.

Background Water requirements increases with gestational age. Insufficient water intake causes dehydration, which may adversely affect maternal health and birth outcomes. However, few related studies have been conducted. The purposes are to assess the water intake and hydration state among pregnant women, and to investigate the associations with pregnancy complications and maternal and infant outcomes. Methods A prospective observational cohort study will be applied. A total of 380 pregnant women will be recruited from the First Affiliated Hospital of Hainan Medical University. Hydration biomarkers and health outcomes will be tested during 15~17 weeks’ gestation, 20~22 weeks’ gestation, 30~32 weeks’ gestation, during childbirth and 42 days after childbirth. Daily fluid intake will be collected using a 24-h fluid intake record for 7 consecutive days. A semi-quantified food frequency method will be used to assess food intake and water intake from food. Anthropometric measurement will be taken following standardized processes. Intracellular fluid (ICF) and extracellular fluid (ECF) will be measured using a body composition analyzer. Morning fasting urine and blood osmolality will be tested by laboratory physicians using an osmotic pressure molar concentration meter. Pregnancy complications will be assessed and diagnosed throughout pregnancy and childbirth. Maternal-infant outcomes will be monitored using related indicators and technologies. In order to explore the internal mechanism and interactions from the perspective of endocrine, pregnancy related hormones (estradiol, prolactin, progesterone) and the hydration-related hormones (copeptin) will be tested during pregnancy. A mixed model of repeated measures ANOVA will be analyzed using SAS 9.2. Results The results may provide basic data on water intake among pregnant women. The association between hydration state and maternal-infant outcomes will also be explored. Conclusions This preliminary exploratory study findings will fill the gaps in the research on water intake, hydration and maternal health, birth outcomes, provide scientific reference data for updating recommendation on water adequate intake among pregnant women, and provide suggestion for developing water intake interventions. Trial registration The protocol has been registered on the website of Chinese Clinical Trial Registry. The Identifier code is ChiCTR1800019284. The Registry date is 3 November, 2018. Registry name is “Study for the correlation between hydration state and pregnancy complications, maternal and infant outcomes during pregnancy”.

Additional file :1 Figure S1. Comparison of pollen viability of four generations of C. Ă hytivus allotetraploid (S4, S8, S11 and S14). Figure S2. Locations and density of 27,392 oligos along the sequence map of cucumber chromosomes 5 (a) and 7 (b). Figure S3. Two translocations carrying C5-oligo signals were detected in other PMCs from the same individual as Fig. 5. Figure S4. Tracing chromosome pairing at meiotic pachytene of S4 generation. Figure S5. Three representative PMCs with multivalents and one lagged C-bivalent at metaphase I in S4 generation. Figure S6. A heatmap depicting the frequency of different lagged bivalent numbers in the asynchronous meiotic PMCs of the S4 and S14 generation.

Stresses caused by heat and Phytophthora capsici infection reduce pepper (Capsicum annuum) yields; however, little is known about their combined effects on pepper. In this study, the combination of heat and P. capsici infection resulted in worse symptoms, including increased heat stress injury, cell death, relative electrical conductivity, and decreased root activity, than either individual stress. The symptoms were more obvious in the susceptible pepper cultivar ‘Early Calwonder’ (EC) than in the resistant landrace line ‘Criollo de Morelos 334’ (CM334). Under heat stress alone, the expression levels of three tested C. annuum heat-shock protein (CaHSP) genes were enhanced in both ‘CM334’ and ‘EC’; however, under the combined stress, their expression levels increased in ‘CM334,’ but decreased in ‘EC.’ Among four defense-related genes, under stress treatments, only two were up-regulated in ‘CM334’ and ‘EC,’ respectively, and both showed higher levels under the combined stress than under the individual stresses. Under the combined stress, the expression levels of three tested Ca2+-signaling pathway genes were enhanced in ‘EC,’ but inhibited in ‘CM334’ compared with either heat or P. capsici infection. Compared with the effects caused by either heat or P. capsici infection, the CaWRKY expression levels were restored to nearly normal levels under the combined stress, and the number of up-regulated genes was higher in ‘CM334’ than in ‘EC.’ Thus, the molecular responses of pepper to the combined stress of heat and P. capsici infection are different from those caused by individual stresses, and the stresses interaction is different between resistant and susceptible pepper germplasms.

The halogen (X = Cl, Br) atom-substituted oxyhalide borate crystal materials RbNa2B6O10Cl (RNBC) and RbNa2B6O10Br (RNBB) with different oxygen vacancies were successfully prepared by high-temperature solid-phase method. Due to the Cl atom has a larger electronegative property can bring a greater deformation compared with Br atom, resulting in a larger oxygen vacancies concentration in the crystal. ESR tests also confirmed that the oxygen vacancy concentration of RNBC was higher than that of RNBB. The different alignment of B6O13 groups in two materials cause a non-central symmetric for RNBC and central symmetric for RNBB, this brought a built –in electric field existing in the RNBC which facilitate the electrons and holes separation when the light irradiation on the surface of the material. The photocatalytic activity of 2-CP under UV light irradiation showed that the degradation efficiency of RNBC was superior to RNBB, and the reaction rate constants of RNBC and RNBB were 0.1577 and 0.1257 min−1 respectively. Active radical experiments confirmed that in the photo-degradation of 2-CP, the O2– was the main active species and followed by e−, h+, OH.

Allopolyploids are often faced with the challenge of maintaining well-coordination between nuclear and cytoplasmic genes inherited from different species. The synthetic allotetraploid Cucumis &times, hytivus is a useful model to explore cytonuclear coevolution. In this study, the sequences and expression of cytonuclear enzyme complex RuBisCO as well as its content and activity in C. &times, hytivus were compared to its parents to explore plastid&ndash, nuclear coevolution. The plastome-coded rbcL gene sequence was confirmed to be stable maternal inheritance, and parental copy of nuclear rbcS genes were both preserved in C. &times, hytivus. Thus, the maternal plastid may interact with the biparentally inherited rbcS alleles. The expression of the rbcS gene of C-homoeologs (paternal) was significantly higher than that of H-homoeologs (maternal) in C. &times, hytivus (HHCC). Protein interaction prediction analysis showed that the rbcL protein has stronger binding affinity to the paternal copy of rbcS protein than that of maternal copy in C. &times, hytivus, which might explain the transcriptional bias of the rbcS homoeologs. Moreover, both the activity and content of RuBisCO in C. &times, hytivus showed mid-parent heterosis. In summary, our results indicate a paternal transcriptional bias of the rbcS genes in C. &times, hytivus, and we found new nuclear&ndash, cytoplasmic combination may be one of the reasons for allopolyploids heterosis.

Abiotic stresses negatively affect plants growth and development by inducing protein denaturation, and autophagy degrades the damaged proteins to alleviate their toxicity, however, little is known about the involvement of autophagy in pepper (Capsicum annuum L.) tolerances to abiotic stresses. In this study, we identified autophagy-related gene (ATG) members in the whole genome of pepper by HMM method and analyzed their expression profiles in response to heat and other abiotic stresses by quantitative real-time PCR. The results showed that the CaATG contained 15 core ATG members including 29 ATG proteins with their respective conserved functional domains, involving the whole process of autophagy. Under normal environmental condition, the expression of CaATG genes showed tissue- and developmental stage-specific patterns, while under abiotic stresses of salt, drought, heat, cold and carbohydrate starvation, the accumulation of autophagosome punctate increased and the expression level of CaATG genes changed with stress type-dependent pattern, which indicates the linkage of autophagy in pepper response to abiotic stresses. After treated with heat stress, both the number of up-regulated CaATG genes and the increment of autophagosome punctate were higher in pepper thermotolerant line R9 than those in thermosensitive line B6, implying an association of autophagy with heat tolerance. In addition, CaATG6 was predicted to interact with CaHSP90 family members. Our study suggests that autophagy is connected to pepper tolerances to heat and other abiotic stresses.

The Hsp20 genes are present in all plant species and play important roles in alleviating heat stress and enhancing plant thermotolerance by preventing the irreversible aggregation of denaturing proteins. However, very little is known about the CaHsp20 gene family in pepper (Capsicum annuum L.), an important vegetable crop with character of temperate but thermosensitive. In this study, a total of 35 putative pepper Hsp20 genes (CaHsp20s) were identified and renamed on the basis of their molecular weight, and then their gene structure, genome location, gene duplication, phylogenetic relationship, and interaction network were also analyzed. The expression patterns of CaHsp20 genes in four different tissues (root, stem, leaf, and flower) from the thermotolerant line R9 under heat stress condition were measured using semi-quantitative RT-PCR. The transcripts of most CaHsp20 genes maintained a low level in all of the four tissues under normal temperature condition, but were highly induced by heat stress, while the expression of CaHsp16.6b, 16.7, and 23.8 were only detected in specific tissues and were not so sensitive to heat stress like other CaHsp20 genes. In addition, compared to those in thermotolerant line R9, the expression peak of most CaHsp20 genes in thermosensitive line B6 under heat stress was hysteretic, and several CaHsp20 genes (CaHsp16.4, 18.2a, 18.7, 21.2, 22.0, 25.8, and 25.9) showed higher expression levels in both line B6 and R9. These data suggest that the CaHsp20 genes may be involved in heat stress and defense responses in pepper, which provides the basis for further functional analyses of CaHsp20s in the formation of pepper acquired thermotoleance.

Pepper (Capsicum annuum L.) is sensitive to heat stress (HS). Heat shock proteins 70 (Hsp70s) play a crucial role in protecting plant cells against HS and control varies characters in different plants. However, CaHsp70-1 gene was not well characterized in pepper. In this study, CaHsp70-1 was cloned from the pepper thermotolerant line R9, which encoded a protein of 652 amino acids, with a molecular weight of 71.54 kDa and an isoelectric point of 5.20. CaHsp70-1 belongs to the cytosolic Hsp70 subgroup, and best matched with tomato SlHsp70. CaHsp70-1 was highly induced in root, stem, leaf and flower in R9 with HS treatment (40 °C for 2 h). In both thermosensitive line B6 and thermotolerant line R9, CaHsp70-1 significantly increased after 0.5 h of HS (40 °C), and maintained in a higher level after 4 h HS. The expression of CaHsp70-1 induced by CaCl2, H2O2 and putrescine (Put) under HS were difference between B6 and R9 lines. The different expression patterns may be related to the differences in promoters of CaHsp70-1 from the two lines. These results suggest that CaHsp70-1 as a member of cytosolic Hsp70 subgroup, may be involved in HS defense response via a signal transduction pathway contained Ca2+, H2O2 and Put.

Background Heat shock factors (Hsfs) play crucial roles in plant developmental and defence processes. The production and quality of pepper (Capsicum annuum L.), an economically important vegetable crop, are severely reduced by adverse environmental stress conditions, such as heat, salt and osmotic stress. Although the pepper genome has been fully sequenced, the characterization of the Hsf gene family under abiotic stress conditions remains incomplete. Results A total of 25 CaHsf members were identified in the pepper genome by bioinformatics analysis and PCR assays. They were grouped into three classes, CaHsfA, B and C, based on highly conserved Hsf domains, were distributed over 11 of 12 chromosomes, with none found on chromosome 11, and all of them, except CaHsfA5, formed a protein–protein interaction network. According to the RNA-seq data of pepper cultivar CM334, most CaHsf members were expressed in at least one tissue among root, stem, leaf, pericarp and placenta. Quantitative real-time PCR assays showed that all of the CaHsfs responded to heat stress (40 °C for 2 h), except CaHsfC1 in thermotolerant line R9 leaves, and that the expression patterns were different from those in thermosensitive line B6. Many CaHsfs were also regulated by salt and osmotic stresses, as well as exogenous Ca2+, putrescine, abscisic acid and methyl jasmonate. Additionally, CaHsfA2 was located in the nucleus and had transcriptional activity, consistent with the typical features of Hsfs. Time-course expression profiling of CaHsfA2 in response to heat stress revealed differences in its expression level and pattern between the pepper thermosensitive line B6 and thermotolerant line R9. Conclusions Twenty-five Hsf genes were identified in the pepper genome and most of them responded to heat, salt, osmotic stress, and exogenous substances, which provided potential clues for further analyses of CaHsfs functions in various kinds of abiotic stresses and of corresponding signal transduction pathways in pepper. Electronic supplementary material The online version of this article (doi:10.1186/s12870-015-0512-7) contains supplementary material, which is available to authorized users.