Inhibitory effect of berberine hydrochloride against Candida albicans and the role of the HOG-MAPK pathway.

Berberine hydrochloride (BH), an active component of Coptis chinensis and other plant taxa, has broad antimicrobial activity and may be useful for the treatment of Candida infections. In this study, the mechanisms underlying the inhibitory effect of BH against Candida albicans were evaluated, with a focus on the high-osmolarity glycerol mitogen-activated protein kinase (HOG-MAPK) pathway, which regulates multiple physiological functions. BH (256 and 64 µg ml-1) significantly increased intracellular glycerol and ROS levels in C. albicans, inhibited germ tube and hyphal formation, and increased chitin and ß-1,3-glucan exposure on the cell wall. The inhibitory effect of BH was positively correlated with its concentration, and the inhibitory effect of 256 µg ml-1 BH was greater than that of 4 µg ml-1 fluconazole (FLC). Furthermore, RT-PCR analysis showed that 256 and 64 µg ml-1 BH altered the HOG-MAPK pathway in C. albicans. In particular, the upregulation of the core genes, SLN1, SSK2, HOG1, and PBS2 may affect the expression of key downstream factors related to glycerol synthesis and osmotic pressure (GPD1), ROS accumulation (ATP11 and SOD2), germ tube and hyphal formation (HWP1), and cell wall integrity (CHS3 and GSC1). BH affects multiple biological processes in C. albicans; thus, it can be an effective alternative to conventional azole antifungal agents.

Abscisic acid enhances resistance to Alternaria solani in tomato seedlings.

The plant hormone abscisic acid (ABA) is an important regulator in many aspects of plant growth and development, as well as stress resistance. Here, we investigated the effects of exogenous ABA application on the interaction between tomato (Solanum lycopersicon L.) and Alternaria solani (early blight). Foliar spraying of 7.58 µM ABA was effective in reducing disease severity in tomato plants. Previously, increased activities of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POD) were observed in exogenous ABA-treated tomato leaves. Moreover, these enzyme activities were maintained at higher levels in ABA-pretreated and A. solani challenged tomato plants. Tomato defense genes, such as PR1, ß-1, 3-glucanase (GLU), PPO, POD, and superoxide dismutase (SOD), were rapidly and significantly up-regulated by exogenous ABA treatment. Furthermore, a subsequent challenge of ABA-pretreated plants with the pathogen A. solani resulted in higher expression of defense genes, compared to water-treated or A. solani inoculated plants. Therefore, our results suggest that exogenous ABA could enhance disease resistance against A. solani infection in tomato through the activation of defense genes and via the enhancement of defense-related enzymatic activities.

Synthesis, (1-->3)-beta-D-glucanase-binding ability and phytoalexin-elicitor activity of (R)-2,3-epoxypropyl (1-->3)-beta-D-pentaglucoside.

The (1-->3)-beta-D-pentaglucoside was synthesized as its (R)-2,3-epoxypropyl glycoside via 2+3 strategy. The disaccharide donor 8 was obtained by 3-selective coupling of 2 with 4, followed by deallylation, and trichloroacetimidation. Meanwhile, the trisaccharide acceptor 12 was prepared by coupling of 10 with 4, followed by deacetylation. Condensation of 8 with 12, followed by epoxidation, and deprotection, gave the target pentaoside. The results of these bioassays demonstrated that the (1-->3)-beta-D-glucanase was obviously inactivated by 15 with k(app)=3.79 x 10(-4) min(-1). At the same time, we found that the 15 was more active as compared to the laminaripentaose in eliciting phytoalexin accumulation in tobacco cotyledon tissue, and it could be kept longer time than laminaripentaose, which indicated it is much more stable than laminaripentaose.