Xo2276 is a putative transcription activator-like effector (TALE) in Xanthomonas oryzae pv. oryzae (Xoo). Xo2276 was expressed with a TAP-tag at the C-terminus in Xoo cells to enable quantitative analysis of protein expression and secretion. Nearly all TAP-tagged Xo2276 existed in an insoluble form; addition of rice leaf extracts from a Xoo-susceptible rice cultivar, Milyang23, significantly stimulated secretion of TAP-tagged Xo2276 into the medium. In a T3SS-defective Xoo mutant strain, secretion of TAP-tagged Xo2276 was blocked. Xo2276 is a Xoo ortholog of Xanthomonas campestris pv. vesicatoria (Xcv) AvrBs3 and contains a conserved DNA-binding domain (DBD), which includes 19.5 tandem repeats of 34 amino acids. Xo2276- DBD was expressed in E. coli and purified. Direct in vitro recognition of Xo2276-DBD on a putative target DNA sequence was confirmed using an electrophoretic mobility shift assay. This is the first study measuring the homologous expression and secretion of Xo2276 in vitro using rice leaf extract and its direct in vitro binding to the specific target DNA sequence.
Terminalia catappa is a widespread medium tree species in many tropical countries. While the majority of the studies up to date focuses on the aerial part of the plant such as leaf, stem bark and fruit, information about the phytochemical property as well as the biological property of the edible seed is still scarce. This study was the first to explore the fatty acid composition, antibacterial and antioxidant activities of the seed oil from T. catappa grown in Vietnam. The results showed that both the hot-pressed and cold-pressed oils contained a high level of unsaturated fatty acids such as oleic (~32%) and linoleic acids (28.38%-29.2%), as well as saturated fatty acids such as palmitic acid (~33.3%-33.61%). The presence of eicosadienoic acid in T. catappa seed oils was reported in this study for the first time. These oils displayed antibacterial activity against 5 out of 12 tested strains such as Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Vibrio parahaemolyticus. The antioxidant activity of the oils was also recorded by DPPH radical scavenging assays with IC50 values of 950 µg/ml and 2529 µg/ml for cold-pressed oil and hot-pressed oil respectively. This study has provided promising extracting methods and resulted in oils that could be good candidates for developing food sources with valuable fatty acids, antioxidant and antibacterial capacities against both Gram-positive and negative bacteria in the human diet.
Curcuma thorelii Gagnep. and Curcuma cotuana Luu, Škorni?k. & H.?.Tr?n are the rare species only found in Southeast Asia. The present study was the first to explore the chemical compositions and antibacterial effects of the whole plant acetone extracts of these 2 species. Altogether 41 and 31 compounds have been identified in C. thorelii and C. cotuana extracts by gas chromatography/mass spectrometry. Accordingly, the C. thorelii extract contained (E)-labda-8(17),12-diene-15,16-dial (33.37%), vitamin E (12.33%), phytol (9.83%) as the major compounds while C. cotuana extract contained predominantly (E)-labda-8(17),12-diene-15,16-dial (14.58%), n-hexadecanoic acid (10.96%), 3,7,11,15-tetramethylhexadec-2-en-1-yl acetate (8.13%), ?-sitosterol (7.97%). In addition, results from disc diffusion assay have shown that C. thorelii acetone extract had inhibitory effects on 5 out of 10 pathogenic bacterial strains such as Bacillus cereus (ATCC 11778), Listeria monocytogenes (ATCC 19111), Staphylococcus aureus (ATCC 25923), S. aureus (ATCC 29213) and S. saprophyticus (BAA750) while C. cotuana acetone extract was found to be effective only against B. cereus. The obtained results showed that the acetone extracts of C. thorelii and C. cotuana possessed several valuable bioactive compounds as well as promising antibacterial activity, which place a good foundation for future pharmaceutical product development.
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