Insights into drought stress response mechanism of tobacco during seed germination by integrated analysis of transcriptome and metabolome.

Drought stress inhibits seed germination, plant growth and development of tobacco, and seriously affects the yield and quality of tobacco leaves. However, the molecular mechanism underlying tobacco drought stress response remains largely unknown. In this study, integrated analysis of transcriptome and metabolome was performed on the germinated seeds of a cultivated variety K326 and its EMS mutagenic mutant M28 with great drought tolerance. The result showed that drought stress inhibited seed germination of the both varieties, while the germination rate of M28 was faster than that of K326 under drought stress. Besides, the levels of phytohormone ABA, GA19, and zeatin were increased by drought stress in M28. Five vital pathways were identified through integrated transcriptomic and metabolomic analysis, including zeatin biosynthesis, aspartate and glutamate synthesis, phenylamine metabolism, glutathione metabolism, and phenylpropanoid synthesis. Furthermore, 20 key metabolites in the above pathways were selected for further analysis of gene modular-trait relationship, and then four highly correlated modules were found. Then analysis of gene expression network was carried out of Top30 hub gene of these four modules, and 9 key candidate genes were identified, including HSP70s, XTH16s, APX, PHI-1, 14-3-3, SCP, PPO. In conclusion, our study uncovered some key drought-responsive pathways and genes of tobacco during seeds germination, providing new insights into the regulatory mechanisms of tobacco drought stress response.

Design, synthesis and antimicrobial evaluation of novel benzoxazole derivatives.

The synthesis of (S)-2-(4-tert-butylphenoxy)-3-(benzoxazol-5-yl) propanoic acid derivatives (2a-k) were described and their in vitro antibacterial activities were determined against Gram-negative and -positive bacteria. These compounds were found to exert a broad spectrum of activity against the screened bacteria, but poor MIC values were found for Candida albicans fungi. Compound 2b bearing a hydrophobic aromatic tie was the most active derivative against all bacteria studied with MIC values ranging from 0.098 to 0.78 µg/mL. The activity of 2b against B. subtilis was 2-fold higher than Penicillin, and 8- to 510-fold higher than other control antibiotics.

Synthesis and antimicrobial evaluation of 3-methanone-6-substituted-benzofuran derivatives.

Seventeen benzofuran derivatives were synthesized and screened for their antibacterial activities against Escherichia coli, Staphylococcus aureus, Methicillin-resistant S. aureus, Bacillus subtilis, and Pseudomonas aeruginosa. Seven of them have showed excellent antibacterial activities compared to the positive controls (Cefotaxime and Sodium Penicillin). The substitutions at C-6 and C-3 positions of these derivatives were found to greatly impact on the antibacterial activity and strains specificity, respectively. Specifically, compounds bearing a hydroxyl group at C-6 (5a, 5b, 5c and 12) offered excellent antibacterial activities against all five above-mentioned strains (MIC(80) = 0.78-12.5 ug/mL), and those with imine (15) and (3, 4, 5-trimethoxyphenyl) methanone (7e), respectively, at C-3 position showed selective activity against S. aureus among five tested strains with great MIC(80) values (3.12-12.5 ug/mL).

Design, synthesis and antimicrobial activity of chiral 2-(substituted-hydroxyl)-3-(benzo[d]oxazol-5-yl)propanoic acid derivatives.

Chiral 2-(substituted-hydroxyl)-3-(benzo[d]oxazol-5-yl)propanoic acid derivatives were synthesized and their antibacterial activities were evaluated against fungus, Gram-negative and Gram-positive bacteria. In general, these compounds showed in vitro activities against all screened Gram-negative and Gram-positive bacteria, but poor MIC values for fungus Candida albicans. Remarkably, the (S)-configuration-substituted phenoxyl side chain on position 2 of propanoic acid exerted excellent antibacterial activity against all screened bacteria. Preliminary structure-activity studies revealed that the hydrophobic substitutes, para-tert-butyl (11r), para-phenyl (11s) and para-benzyloxy (11t) on the phenoxyl side chain displayed best activities against all Gram-negative and Gram-positive bacteria with MIC values between 1.56 and 6.25 µg/mL.

Synthesis and antimicrobial evaluation of new benzofuran derivatives.

Thirteen compounds, based on benzofuran skeleton bearing aryl substituents at its C-3 position through methanone linker, were synthesized and screened for their antibacterial and antifungal activities against four bacteria Escherichia coli, Staphylococcus aureus, Methicillin-resistant S.aureus, Bacillus subtilis, and a fungus Candida albicans. Four hydrophobic benzofuran analogs were found to exhibit favorable antibacterial activities (MIC(80) = 0.39-3.12 µg/mL), which were better than the control drugs.