At3g53630 encodes a GUN1-interacting protein under norflurazon treatment

Chloroplasts are semi-autonomous organelles, with more than 95% of their proteins encoded by the nuclear genome. The chloroplast-to-nucleus retrograde signals are critical for the nucleus to coordinate its gene expression for optimizing or repairing chloroplast functions in response to changing environments. In chloroplasts, the pentatricopeptide-repeat protein GENOMES UNCOUPLED 1 (GUN1) is a master switch that senses aberrant physiological states, such as the photooxidative stress induced by norflurazon (NF) treatment, and represses the expression of photosynthesis-associated nuclear genes (PhANGs). However, it is largely unknown how the retrograde signal is transmitted beyond GUN1. In this study, a protein GUN1-INTERACTING PROTEIN 1 (GIP1), encoded by At3g53630, was identified to interact with GUN1 by different approaches. We demonstrated that GIP1 has both cytosol and chloroplast localizations, and its abundance in chloroplasts is enhanced by NF treatment with the presence of GUN1. Our results suggest that GIP1 and GUN1 may function antagonistically in the retrograde signaling pathway.

     

Enhanced production of a novel cytotoxic chromone oxalicumone A by marine-derived mutant Penicillium oxalicum SCSIO 24–2

Many marine natural products hold great potential for the development of new and much needed drugs. However, the production of active metabolites by marine-derived microorganisms is usually very low, and large-scale culture has to be involved to meet the need of chemical structural modification and deep pharmacy study. In order to enhance the production of a novel cytotoxic sulfur-containing chromone oxalicumone A (OA), germinating spores of a marine-derived wild strain Penicillium oxalicum SCSGAF 0023 were mutated by microwave and ultraviolet light irradiation, which led to the obtainment of a mutant P. oxalicum SCSIO 24–2 that could produce fivefold increase in OA production (3.42?±?0.21 mg/l) as compared to the wild strain. This is the first report that germinating spores are applied in marine-derived Penicillium sp. mutating to enhance the production of OA. Further, Plackett–Burman design and central composite design were adopted to optimize the basic medium components for increasing OA production by the mutant SCSIO 24–2 in shake flasks. The results indicated that three medium components including mannitol, maltose, and l-cysteine had significant effects on OA production, and their concentrations were optimized as 36, 27.9, and 0.99 g/l, respectively. In the optimized medium, the OA production (18.31?±?0.27 mg/l) by mutant SCSIO 24–2 was 4.4-fold higher than that in the basic medium. These results of this work promise to improve the present production of OA and may be adopted to enhance other objective products' production by marine-derived fungi.     

Production and chitinase-binding ability of lipo-chitopentaose nodulation factor

The penta-N-acetyl-chitopentaose 2 has been prepared by using recombinant E. coli strains harboring the nodC gene (encoding chitooligosaccharide synthase) from Azorhizobium caulinodans. Then, the deacetylase NodB removed the N-acetyl moiety from the nonreducing terminus of 2 to give tetra-N-acetyl-chitopentaose 3. N-Acylation of 3 with stearyl chloride was performed in DMF containing water and provided the corresponding lipo-chitopentaose nodulation factor 4. A binding chitinase assay indicated that 4 was much more stable than 3.     

Synthesis of (R)-2,3-epoxypropyl(1-->3)-beta-D-pentaglucoside

The title pentasaccharide was synthesized via a 2+3 strategy. The disaccharide donor, 3-O-acetyl-2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranosyl-(1-->3)-2-O-benzoyl-4,6-O-benzylidene-alpha-D-glucopyranosyl trichloroacetimidate (8), was obtained by selective coupling of allyl 2-O-benzoyl-4,6-O-benzylidene-alpha-D-glucopyranoside with 3-O-acetyl-2-O-benzoyl-4,6-O-benzylidene-alpha-D-glucopyranosyl trichloroacetimidate (4), followed by deallylation, and trichloroacetimidation. Meanwhile, the trisaccharide acceptor, allyl 2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranosyl-(1-->3)-2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranosyl-(1-->3)-2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranoside (12), was prepared by coupling of allyl 2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranosyl-(1-->3)-2-O-benzoyl-4,6-O-benzylidene-beta-D-glucopyranoside with 4, followed by deacetylation. Condensation of 8 with 12, followed by epoxidation, and deprotection, gave the target pentaoside.     

Production and chitinase-binding ability of lipo-chitopentaose nodulation factor

The penta-N-acetyl-chitopentaose 2 has been prepared by using recombinant E. coli strains harboring the nodC gene (encoding chitooligosaccharide synthase) from Azorhizobium caulinodans. Then, the deacetylase NodB removed the N-acetyl moiety from the nonreducing terminus of 2 to give tetra-N-acetyl-chitopentaose 3. N-Acylation of 3 with stearyl chloride was performed in DMF containing water and provided the corresponding lipo-chitopentaose nodulation factor 4. A binding chitinase assay indicated that 4 was much more stable than 3.     

A new fermentation process allows large-scale production of tetra-N-acetyl-chitotetraosyl allosamizoline

A new compound 2, possessing a tetra-N-acetyl-chitotetraosyl moiety as a constituent, was synthesized by bacterial fermentation, which used allosamizoline 1 as the initial acceptor. A 2-binding chitinase assay, indicated that the chitinase was inactivated by 2 with IC₅₀ = 0.03 μg/mL.     

Antifouling potentials of eight deep-sea-derived fungi from the South China Sea

Marine-derived microbial secondary metabolites are promising potential sources of nontoxic antifouling agents. The search for environmentally friendly and low-toxic antifouling components guided us to investigate the antifouling potentials of eight novel fungal isolates from deep-sea sediments of the South China Sea. Sixteen crude ethyl acetate extracts of the eight fungal isolates showed distinct antibacterial activity against three marine bacteria (Loktanella hongkongensis UST950701–009, Micrococcus luteus UST950701–006 and Pseudoalteromonas piscida UST010620–005), or significant antilarval activity against larval settlement of bryozoan Bugula neritina. Furthermore, the extract of Aspergillus westerdijkiae DFFSCS013 displayed strong antifouling activity in a field trial lasting 4 months. By further bioassay-guided isolation, five antifouling alkaloids including brevianamide F, circumdatin F and L, notoamide C, and 5-chlorosclerotiamide were isolated from the extract of A. westerdijkiae DFFSCS013. This is the first report about the antifouling potentials of metabolites of the deep-sea-derived fungi from the South China Sea, and the first stage towards the development of non- or low-toxic antifouling agents from deep-sea-derived fungi.     

Chemo-enzymatic synthesis of tetra-N-acetyl-chitotetraosyl allosamizoline

A new compound 7, possessing a tetra-N-acetyl-chitotetraosyl moiety as a constituent, was synthesized by bacterial fermentation which used allosamizoline 6 as the initial acceptor.