| 1. |
- Guerriero, Gea, et al.
(författare)
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What Do We Really Know about Cellulose Biosynthesis in Higher Plants?
- 2010
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Ingår i: JOURNAL OF INTEGRATIVE PLANT BIOLOGY. - : Wiley. - 1672-9072 .- 1744-7909. ; 52:2, s. 161-175
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Forskningsöversikt (refereegranskat)abstract
- Cellulose biosynthesis is one of the most important biochemical processes in plant biology. Despite the considerable progress made during the last decade, numerous fundamental questions related to this key process in plant development are outstanding. Numerous models have been proposed through the years to explain the detailed molecular events of cellulose biosynthesis. Almost all models integrate solid experimental data with hypotheses on several of the steps involved in the process. Speculative models are most useful to stimulate further research investigations and bring new exciting ideas to the field. However, it is important to keep their hypothetical nature in mind and be aware of the risk that some undemonstrated hypotheses may progressively become admitted. In this review, we discuss the different steps required for cellulose formation and crystallization, and highlight the most important specific aspects that are supported by solid experimental data.
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| 2. |
- Meijer, Johan
(författare)
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Characterization of a Novel beta-thioglucosidase CpTGG1 in Carica papaya and its Substrate-dependent and Ascorbic Acid-independent O-beta-glucosidase Activity
- 2010
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Ingår i: Journal of Integrative Plant Biology. - : Wiley. - 1672-9072 .- 1744-7909. ; 52, s. 879-890
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Tidskriftsartikel (refereegranskat)abstract
- Plant thioglucosidases are the only known S-glycosidases in the large superfamily of glycosidases. These enzymes evolved more recently and are distributed mainly in Brassicales. Thioglucosidase research has focused mainly on the cruciferous crops due to their economic importance and cancer preventive benefits. In this study, we cloned a novel myrosinase gene, CpTGG1, from Carica papaya Linnaeus. and showed that it was expressed in the aboveground tissues in planta. The recombinant CpTGG1 expressed in Pichia pastoris catalyzed the hydrolysis of both sinigrin and glucotropaeolin (the only thioglucoside present in papaya), showing that CpTGG1 was indeed a functional myrosinase gene. Sequence alignment analysis indicated that CpTGG1 contained all the motifs conserved in functional myrosinases from crucifers, except for two aglycon-binding motifs, suggesting substrate priority variation of the non-cruciferous myrosinases. Using sinigrin as substrate, the apparent K-m and V-max values of recombinant CpTGG1 were 2.82 mM and 59.9 mu mol min-1 mg protein-1, respectively. The K-cat/K-m value was 23 s-1 mM-1. O-beta-glucosidase activity towards a variety of substrates were tested, CpTGG1 displayed substrate-dependent and ascorbic acid-independent O-beta-glucosidase activity towards 2-nitrophenyl-beta-D-glucopyranoside and 4-nitrophenyl-beta-D-glucopyranoside, but was inactive towards glucovanillin and n-octyl-beta-D-glucopyranoside. Phylogenetic analysis indicated CpTGG1 belongs to the MYR II subfamily of myrosinases.
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| 3. |
- Cifuentes, Carolina, et al.
(författare)
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Biosynthesis of Callose and Cellulose by Detergent Extracts of Tobacco Cell Membranes and Quantification of the Polymers Synthesized in vitro
- 2010
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Ingår i: J INTEGR PLANT BIOL. - : Wiley. - 1672-9072. ; 52:2, s. 221-233
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Tidskriftsartikel (refereegranskat)abstract
- The conditions that favor the in vitro synthesis of cellulose from tobacco BY-2 cell extracts were determined. The procedure leading to the highest yield of cellulose consisted of incubating digitonin extracts of membranes from 11-day-old tobacco BY-2 cells in the presence of 1 mM UDP-glucose, 8 mM Ca2+ and 8 mM Mg2+. Under these conditions, up to nearly 40% of the polysaccharides synthesized in vitro corresponded to cellulose, the other polymer synthesized being callose. Transmission electron microscopy analysis revealed the occurrence of two types of structures in the synthetic reactions. The first type consisted of small aggregates with a diameter between 3 and 5 nm that associated to form fibrillar strings of a maximum length of 400 nm. These structures were sensitive to the acetic/nitric acid treatment of Updegraff and corresponded to callose. The second type of structures was resistant to the Updegraff reagent and corresponded to straight cellulose microfibrils of 2-3 nm in diameter and 200 nm to up to 5 mu m in length. In vitro reactions performed on electron microscopy grids indicated that the minimal rate of microfibril elongation in vitro is 120 nm/min. Measurements of retardance by liquid crystal polarization microscopy as a function of time showed that small groups of microfibrils increased in retardance by up to 0.047 nm/min per pixel, confirming the formation of organized structures.
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| 4. |
- Wingler, Astrid, et al.
(författare)
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Interactions between temperature and sugars in the regulation of leaf senescence in the perennial herb Arabis alpina L.
- 2012
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Ingår i: Journal of integrative plant biology. - : Wiley. - 1744-7909 .- 1672-9072. ; 54:8, s. 595-605
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Tidskriftsartikel (refereegranskat)abstract
- Annual plants usually flower and set seed once before senescence results in the death of the whole plant (monocarpic senescence). Leaf senescence also occurs in polycarpic perennials; even in "evergreen" species individual leaves senesce. In the annual model Arabidopsis thaliana sugars accumulate in the senescent leaves and senescence is accelerated by high sugar availability. Similar to A. thaliana, sugar contents increased with leaf age in the perennial Arabis alpina grown under warm conditions (22 °C day/18 night). At 5 °C, sugar contents in non-senescent leaves were higher than at a warm temperature, but dependent on the accession, either sugars did not accumulate or their contents decreased in old leaves. In A. alpina plants grown in their natural habitat in the Alps, sugar contents declined with leaf age. Growth at a cold temperature slightly delayed senescence in A. alpina. In both warm and cold conditions, an external glucose supply accelerated senescence, but natural variation was found in this response. In conclusion, sugar accumulation under warm conditions could accelerate leaf senescence in A. alpina plants, but genotype-specific responses and interactions with growth temperature are likely to influence senescence under natural conditions.
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| 5. |
- Chen, Jun‐Tong, et al.
(författare)
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An updated classification for the hyper‐diverse genus Corydalis (Papaveraceae: Fumarioideae) based on phylogenomic and morphological evidence
- 2023
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Ingår i: Journal of Integrative Plant Biology. - : John Wiley & Sons. - 1672-9072 .- 1744-7909. ; 65:9, s. 2138-2156
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Tidskriftsartikel (refereegranskat)abstract
- The genus Corydalis, with ca. 530 species, has long been considered taxonomically challenging because of its great variability. Previous molecular analyses, based on a few molecular markers and incomplete taxonomic sampling, were clearly inadequate to delimit sections and subgenera. We have performed phylogenetic analyses of Corydalis and related taxa, using 65 shared protein-coding plastid genes from 313 accessions (including 280 samples of ca. 226 species of Corydalis) and 152 universal low-copy nuclear genes from 296 accessions (including 271 samples of Corydalis) covering all 42 previously recognized sections and five independent “series”. Phylogenetic trees were inferred using Bayesian Inference and Maximum Likelihood. Eight selected morphological characters were estimated using ancestral state reconstructions. Results include: (i) of the three subgenera of Corydalis, two are fully supported by both the plastid and nuclear data; the third, subg. Cremnocapnos, is weakly supported by plastid DNA only, whereas in the nuclear data the two included sections form successive outgroups to the rest of the genus; (ii) among all 42 sections and five “series”, 25 sections and one “series” are resolved as monophyletic in both data sets; (iii) the common ancestor of Corydalis is likely to be a perennial plant with a taproot, yellow flowers with a short saccate spur, linear fruits with recurved fruiting pedicels, and seeds with elaiosomes; (iv) we provide a new classification of Corydalis with four subgenera (of which subg. Bipapillatae is here newly described), 39 sections, 16 of which are consistent with the previous classification, 16 sections have been recircumscribed, one section has been reinstated and six new sections are established. Characters associated with lifespan, underground structures, floral spur, fruit and elaiosomes are important for the recognition of subgenera and sections. These new phylogenetic analyses combined with ancestral character reconstructions uncovered previously unrecognized relationships, and greatly improved our understanding of the evolution of the genus.
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| 6. |
- Li, Qishuang, et al.
(författare)
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Identification of the cytochrome P450s responsible for the biosynthesis of two types of aporphine alkaloids and their de novo biosynthesis in yeast
- 2024
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Ingår i: Journal of Integrative Plant Biology. - 1672-9072 .- 1744-7909. ; In Press
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Tidskriftsartikel (refereegranskat)abstract
- Aporphine alkaloids have diverse pharmacological activities; however, our understanding of their biosynthesis is relatively limited. Previous studies have classified aporphine alkaloids into two categories based on the configuration and number of substituents of the D-ring and have proposed preliminary biosynthetic pathways for each category. In this study, we identified two specific cytochrome P450 enzymes (CYP80G6 and CYP80Q5) with distinct activities toward (S)-configured and (R)-configured substrates from the herbaceous perennial vine Stephania tetrandra, shedding light on the biosynthetic mechanisms and stereochemical features of these two aporphine alkaloid categories. Additionally, we characterized two CYP719C enzymes (CYP719C3 and CYP719C4) that catalyzed the formation of the methylenedioxy bridge, an essential pharmacophoric group, on the A- and D-rings, respectively, of aporphine alkaloids. Leveraging the functional characterization of these crucial cytochrome P450 enzymes, we reconstructed the biosynthetic pathways for the two types of aporphine alkaloids in budding yeast (Saccharomyces cerevisiae) for the de novo production of compounds such as (R)-glaziovine, (S)-glaziovine, and magnoflorine. This study provides key insight into the biosynthesis of aporphine alkaloids and lays a foundation for producing these valuable compounds through synthetic biology.
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