Cowpea lipid transfer protein 1 regulates plant defense by inhibiting the cysteine protease of cowpea mosaic virus.

Many virus genomes encode proteases that facilitate infection. The molecular mechanism of plant recognition of viral proteases is largely unexplored. Using the system of Vigna unguiculata and cowpea mosaic virus (CPMV), we identified a cowpea lipid transfer protein (LTP1) which interacts with CPMV-encoded 24KPro, a cysteine protease, but not with the enzymatically inactive mutant 24KPro(C166A). Biochemical assays showed that LTP1 inhibited 24KPro proteolytic cleavage of the coat protein precursor large coat protein-small coat protein. Transient overexpression of LTP1 in cowpea reduced CPMV infection, whereas RNA interference-mediated LTP1 silencing increased CPMV accumulation in cowpea. LTP1 is mainly localized in the apoplast of uninfected plant cells, and after CPMV infection, most of the LTP1 is relocated to intracellular compartments, including chloroplast. Moreover, in stable LTP1-transgenic Nicotiana benthamiana plants, LTP1 repressed soybean mosaic virus (SMV) nuclear inclusion a protease activity, and accumulation of SMV was significantly reduced. We propose that cowpea LTP1 suppresses CPMV and SMV accumulation by directly inhibiting viral cysteine protease activity.

Enzymatic synthesis of Vaccinium blue using vaccinoside as a bifunctional precursor.

Since Tang dynasty in China, the fresh leaves of Vaccinium bracteatum (VBL) have been applied as natural pigment to produce black rice. However, detailed information on its biosynthetic mechanism still remained unclear. Following rice dyeing capacity assay, vaccinoside, one of iridoid glycosides, was identified as the key active compound. Increased methodical research demonstrated vaccinoside as a distinct bifunctional precursor, which could be catalyzed by polyphenol oxidase or ß-glucosidase independently, followed by reaction with 15 amino acids to give blue pigments (VBPs; λmax 581-590 nm) of different hues. Two synthetic pathways of VBPs were proposed, using multiple techniques such as HPLC, HPSEC, UV-Vis spectrum and colorimeter as analysis tools. Black rice was interpreted to be prepared by cooking, using vaccinoside, intrinsic enzymes from fresh VBL and rice protein in combination. These findings promote the understanding of VBP formation mechanisms and provide an efficient method of producing novel Vaccinium blue pigments.

The interaction between gut microbiota and flavonoid extract from Smilax glabra Roxb. and its potent alleviation of fatty liver.

Fatty liver is associated with intestinal microbiota dysbiosis and low-grade chronic inflammation. Herein we report the interaction of the flavonoid extract from Smilax glabra Roxb. (FSGR) with gut microbiota. Then, FSGR's function of modulating microbiota in a rat model of high-fat diet (HFD) induced fatty liver has been explored. These investigations indicated that the main compound in FSGR, such as astilbin and its isomers, could be metabolized to aglycone, while further splitting resulted in some phenolic acid compounds through a redox reaction. The data obtained clearly showed that FSGR not only alleviated the steatosis degree of liver cells and modulated the contents of short chain fatty acids (SCFAs) in the intestinal tract, but also reversed gut dysbiosis induced by HFD as prognosticated by the decreased ratio of Firmicutes/Bacteroidetes (F/B) and altered gene expression. The results demonstrated that FSGR probably could be used as a prebiotic agent to impede gut dysbiosis and fatty liver-related metabolic disorders.