Evolution, gene expression, and protein‒protein interaction analyses identify candidate CBL-CIPK signalling networks implicated in stress responses to cold and bacterial infection in citrus.

BACKGROUND: Cold is a major abiotic stress and Huanglongbing and citrus canker disease are two devastating bacterial diseases for citrus. The Ca2+-CBL-CIPK network is known to regulate different types of stress signalling in plants. How do CBL-CIPK signalling networks function in response to cold and infection by CLas or Xcc in citrus? RESULTS: Eight calcineurin B-like proteins (CBLs) and seventeen CBL-interacting protein kinases (CIPKs) were identified from the cold-tolerant satsuma mandarin 'Guijing2501' (Citrus. unshiu) and CLas/Xcc-sensitive sweet orange (C. sinensis). Phylogenetic analysis revealed that both CBL and CIPK family members in citrus were classified into an ancient and a recent clade according to their conserved domain characteristics and/or intron/exon structures. Genome duplication analysis suggested that both tandem and segmental duplications contributed to the amplification of the CBL and CIPK gene families in citrus under intense purifying selection, and the duplication events only existed in the recent clades. Expression comparison of the duplicated gene pairs indicated that the duplicated CBL and CIPK genes underwent functional differentiation. Further expression analysis identified that CBL1, 5, 6, and 8 and CIPK2, 8, 12, 15, 16, and 17 were significantly regulated by multiple stresses, including cold, Xcc infection and/or CLas infection, in citrus, whereas CBL2/7 and CIPK1/4/5/11/13/14 were independently highly regulated by cold and CIPK3 was uniquely responsive to Xcc infection. The combination analyses of targeted Y2H assay and expression analysis revealed that CBL6-CIPK8 was the common signalling network in response to cold and Xcc infection, while CBL6/CBL8-CIPK14 was uniquely responsive to cold in citrus. Further stable transformation and cold tolerance assay indicated that overexpression of CuCIPK16 enhanced the cold tolerance of transgenic Arabidopsis with higher POD activity and lower MDA content. CONCLUSIONS: In this study, evolution, gene expression and protein‒protein interaction analyses of citrus CBLs and CIPKs were comprehensively conducted over a genome-wide range. The results will facilitate future functional characterization of individual citrus CBLs and CIPKs under specific stresses and provide clues for the clarification of cold tolerance and disease susceptibility mechanisms in corresponding citrus cultivars.

Highly efficient enzymatic synthesis of tert-butyl (S)-6-chloro-5-hydroxy-3-oxohexanoate with a mutant alcohol dehydrogenase of Lactobacillus kefir.

tert-Butyl (S)-6-chloro-5-hydroxy-3-oxohexanoate ((S)-CHOH) is a valuable chiral synthon, which is used for the synthesis of the cholesterol-lowering drugs atorvastatin and rosuvastatin. To date, only the alcohol dehydrogenases from Lactobacillus brevis (LbADH) and Lactobacillus kefir (LkADH) have demonstrated catalytic activity toward the asymmetric reduction of tert-butyl 6-chloro-3,5-dioxohexanoate (CDOH) to (S)-CHOH. Herein, a tetrad mutant of LkADH (LkTADH), A94T/F147L/L199H/A202L, was screened to be more efficient in this bioreduction process, exhibiting a 3.7- and 42-fold improvement in specific activity toward CDOH (1.27 U/mg) over LbADH (0.34 U/mg) and wild-type LkADH (0.03 U/mg), respectively. The molecular basis for the improved catalytic activity of LkTADH toward CDOH was investigated using homology modeling and docking analysis. Two major issues had a significant impact on the biocatalytic efficiency of this process, including (i) the poor aqueous stability of the substrate and (ii) partial substrate inhibition. A fed-batch strategy was successfully developed to address these issues and maintain a suitably low substrate concentration throughout the entire process. Several other parameters were also optimized, including the pH, temperature, NADP(+) concentration and cell loading. A final CDOH concentration of 427 mM (100 g/L) gave (S)-CHOH in 94 % yield and 99.5 % e.e. after a reaction time of 38 h with whole cells expressing LkTADH. The space-time yield and turnover number of NADP(+) in this process were 10.6 mmol/L/h and 16,060 mol/mol, respectively, which were the highest values ever reported. This new approach therefore represents a promising alternative for the efficient synthesis of (S)-CHOH.

Functional analysis of flavonoid 3',5'-hydroxylase from tea plant (Camellia sinensis): critical role in the accumulation of catechins.

BACKGROUND: Flavonoid 3',5'-hydroxylase (F3'5'H), an important branch point enzyme in tea plant flavan-3-ol synthesis, belongs to the CYP75A subfamily and catalyzes the conversion of flavones, flavanones, dihydroflavonols and flavonols into 3',4',5'-hydroxylated derivatives. However, whether B-ring hydroxylation occurs at the level of flavanones and/or dihydroflavonols, in vivo remains unknown. RESULTS: The Camellia sinensis F3'5'H (CsF3'5'H) gene was isolated from tea cDNA library. Expression pattern analysis revealed that CsF3'5'H expression was tissue specific, very high in the buds and extremely low in the roots. CsF3'5'H expression was enhanced by light and sucrose. Over-expression of CsF3'5'H produced new-delphinidin derivatives, and increased the cyanidin derivative content of corollas of transgenic tobacco plants, resulting in the deeper transgenic plant flower color. Heterologous expressions of CsF3'5'H in yeast were carried out to demonstrate the function of CsF3'5'H enzyme in vitro. Heterologous expression of the modified CsF3'5'H (CsF3'5'H gene fused with Vitis vinifera signal peptide, FSI) revealed that 4'-hydroxylated flavanone (naringenin, N) is the optimum substrate for CsF3'5'H, and was efficiently converted into both 3'4'- and 3'4'5'-forms. The ratio of 3'4'5'- to 3'4'-hydroxylated products in FSI transgenic cells was significantly higher than VvF3'5'H cells. CONCLUSIONS: CsF3'5'H is a key controller of tri-hydroxyl flavan-3-ol synthesis in tea plants, which can effectively convert 4'-hydroxylated flavanone into 3'4'5'- and/or 3'4'-hydroxylated products. These findings provide animportant basis for further studies of flavonoid biosynthesis in tea plants. Such studies would help accelerate flavonoid metabolic engineering in order to increase B-ring tri-hydroxyl product yields.

[Effects of zhuhong ointment on MMPs activities and production by HSF].

HuaFu Shengji is the primary traditional Chinese medicine (TCM) therapy for treating chronic skin ulcer. The high activities of the protein enzyme in the wound fluids is one of the main cause of healing delay. In order to investigate the effect of TCM Zhuhong ointment for promoting wound healing. This research focused on its influence on matrix metalloproteinase (MMP) activities in wound fluids with TCM Yang syndromes, directly on the activated MMP-1,2 activities in vitro and on MMP-1,-2,-9 production by HSF. 8 wound fluid samples were collected, which were diagnosed Yang Syndromes in TCM. Wound fluid activities of MMP-2 and MMP-9 were measured by gelatin zymogram assay. MMP-1 and MMP-2 activities in vitro were measured by substrate cleavage. CCK-8 was used to observe the toxicity of Zhuhong ointment on HSF. MMP-1,-2,-9 production by HSF were detected by confocal microscope. Zhuhong ointment from 1 to 25 g x L(-1) obviously inhibited MMP-2 activity in wound fluid. When Zhuhong ointment was over 5 g x L(-1), it showed significantly inhibitory effect on wound fluid MMP-9 activity. In vitro study, when the mercury concentration was 320 mg x L(-1), Zhuhong ointment solution directly inhibited both MMP-1 activity and MMP-2. But mercury concentration from 0.51-2.56 mg x L(-1), it could activate MMP-1 activity, and from 0.51-64 mg x L(-1), activate MMP-2 activity instead. The mercury concentration when Zhuhong ointment saturated in DMEM was 39.6 mg x L(-1). When the mercury concentration was over 1.23 mg x L(-1), Zhuhong ointment showed toxicity to HSF. At 1.23, 0.62, 0.31 mg x L(-1) of mercury concentration, it increased MMP-1 expression by HSF, and at 1.23, 0.62 mg x L(-1), decreased MMP-2 expression. However, at 1.23, 0.62, 0.31 mg x L(-1), it decreased MMP-9 expression. At higher concentration, Zhuhong ointment can inhibit MMP-2, MMP-9 activities in wound fluid with dose-dependent way and show a direct inhibitory effect on activated MMP-1 and MMP-2 in vitro. But at a lower concentration, it showed two-way adjustment, with increased MMP-1, MMP-2 activities and its expression by HSF and decreased MMP-9 activity.

Dexamethasone impairs the differentiation and maturation of murine dendritic cells by Toll-like receptor 4-nuclear factor-kappaB pathway.

BACKGROUND: Recent studies have demonstrated that dexamethasone (DEX) interferes with immune responses by targeting key functions of dendritic cells (DCs) at the earliest stage. However, the cellular and molecular mechanisms are still incompletely understood. This study aimed to explore the possible mechanisms by investigating the roles of DEX on differentiation, maturation & function of murine DCs and the effects of DEX on DCs via Toll-like receptor 4 (TLR4)-nuclear factor (NF)-kappaB mediated signal pathway. METHODS: Immature DCs (imDCs) were cultured from murine bone marrow (BM) cells. We added DEX into culture medium at different time. The expression of CD11c, CD86 and I-A(b) (mouse MHC class II molecule) was determined by flow cytometry. We determined the expression of NF-kappaB and its inhibitory protein I-kappaBalpha by electrophoretic mobility shift assay (EMSA) and Western blotting, respectively. The productions of interleukin (IL)-12p70 and IL-10 in cell culture supernatants were determined by enzyme-linked immunosorbent assay (ELISA). RESULTS: DEX impaired differentiation of DCs from murine bone marrow progenitors, and inhibited lipopolysaccharide (LPS) induced maturation of DCs. DEX significantly inhibited NF-kappaB expression of normal DCs, the higher the DEX concentration or the longer the DEX treatment time, the more obvious the effect. However, DEX had little effect on LPS-induced NF-kappaB activation, and partially impaired LPS-induced I-kappaBalpha degradation. DEX significantly decreased LPS induced IL-12p70 production by DCs. Interestingly, our results showed a synergistic effect between DEX and LPS on the production of IL-10 by DCs. CONCLUSIONS: DEX inhibits the differentiation and maturation of murine DCs involved in TLR4-I-kappaB-NF-kappaB pathway, and also indirectly impairs Th1 development and interferes with the Th1-Th2 balance through IL-12 and/or IL-10 secretion by DCs.

[The analysis in the expression of Toll-like receptor 4 mRNA and the effect of dexamethasone on mice dendritic cells by real-time PCR].

AIM: To establish a SYBR Green I quantitative real-time PCR method for detecting the expression of the TLR4 mRNA of mice and to monitor the dynamics for TLR4 mRNA level of mice bone marrow-derived dendritic cells (DC) in the process of the maturation and the effect of dexamethasone (DEX) on TLR4 expression. METHODS: (1) DC from mice bone marrow were induced by cytokines and separated by magnetic beads. (2) The combined plasmid pUCm-T/TLR4 and pUCm-T/beta-actin for the standard materials in the real-time PCR was reconstructed. (3) The dynamics for the express TLR4 mRNA of DC cultivated in vitro for 4, 6, 8, 10, 12 days was detected respectively. (4) The TLR4 mRNA expression between DC treated with or without DEX was detected and compared. RESULTS: (1) The DC with the purity over 90% were fully separated in success. (2) A SYBR Green I quantitative real-time PCR method for analyzing the TLR4 mRNA expression level of the mice was successful established. (3) TLR4 mRNA level was stable early during the culture of DC and then rise obviously at last. CONCLUSION: There exists a close relationship between the level of TLR4 mRNA and the period of maturation of DC and the expression of TLR4 could be increased by DEX.

[Effect of rapamycin and dexamethasone on differentiation and maturation of murine bone marrow-derived dendritic cells].

AIM: To observe the effect of rapamycin (Rap) and dexamethasone (Dex) on differentiation and development of murine bone marrow-derived dendritic cells (DC) in vitro. METHODS: DC cells generated from C57BL/6 murine bone marrow cells were induced by GM-CSF and IL-4. During the course, Rap or Dex was added to the culture and the cells were then stimulated by LPS. (1)Morphology development of DCs was observed by inverted microscope and scanning electron microscope.(2)The cells were analyzed by flow cytometry (FCM) to determine the proportion of CD11c(+) cells and the change of CD86 and MHC class II molecule.(3)The influence of DCs treated by Rap or Dex on the allogeneic T cell proliferation was studied by one-way MLR. RESULTS: (1)The morphology of DCs maintained in a durable state of immaturity after Rap or Dex pretreatment.(2)The expression of CD11c and MHC-II slightly decreased but CD86 dramatically reduced on Rap-treated DC cells. There was close relationship between the expression of CD11c on Dex-treated cells and the dosage of Dex. The surface expression of CD86 and MHC-II dramatically reduced on Dex-treated DCs. Moreover, DCs treated by Rap or Dex were both able to resist the maturation triggered by LPS.(3)Bone marrow-derived DCs cultured with Dex or Rap had a lower stimulatory effect on allogeneic T cells compared with that of mature DCs. CONCLUSION: Rap and Dex could keep DCs in durable immaturity. Compared with Dex, which inhibited the expression of co-stimulatory molecules, Rap hardly influenced the differentiation of DCs and the expression of MHC class II molecules.