Silicon enhances suberization and lignification in roots of rice (Oryza sativa).

The beneficial element silicon (Si) may affect radial oxygen loss (ROL) of rice roots depending on suberization of the exodermis and lignification of sclerenchyma. Thus, the effect of Si nutrition on the oxidation power of rice roots, suberization and lignification was examined. In addition, Si-induced alterations of the transcript levels of 265 genes related to suberin and lignin synthesis were studied by custom-made microarray and quantitative Real Time-PCR. Without Si supply, the oxidation zone of 12 cm long adventitious roots extended along the entire root length but with Si supply the oxidation zone was restricted to 5 cm behind the root tip. This pattern coincided with enhanced suberization of the exodermis and lignification of sclerenchyma by Si supply. Suberization of the exodermis started, with and without Si supply, at 4-5 cm and 8-9 cm distance from the root tip (drt), respectively. Si significantly increased transcript abundance of 12 genes, while two genes had a reduced transcript level. A gene coding for a leucine-rich repeat protein exhibited a 25-fold higher transcript level with Si nutrition. Physiological, histochemical, and molecular-biological data showing that Si has an active impact on rice root anatomy and gene transcription is presented here.

Prediction of flocculation ability of brewing yeast inoculates by flow cytometry, proteome analysis, and mRNA profiling.

The ability of brewing yeast to flocculate is an important feature for brewing of qualitatively good beer. Flocculation involves two main cell wall structures, which are the flocculation proteins (flocculins) and mannans, to which these flocculins bind. Unfortunately, in practice, the flocculation ability may get lost after several repitches. Flow cytometry was employed to analyze glucose and mannose structures of the cell surface by application of fluorescent lectins. Validation of the expression of the flocculin genes Lg-FLO1, FLO1, FLO5, and FLO9 was carried out using microarray techniques. SDS-PAGE, western blot, and ESI-MS/MS analyses served to isolate and determine yeast cell flocculins. Mannose and glucose labeling with fluorescent lectins allowed differentiating powdery and flocculent yeast cells under laboratory conditions. Using microarray techniques and proteomics, the four flocculation genes Lg-FLO1, FLO1, FLO5, FLO9, and the protein Lg-Flo1p were identified as factors of major importance for flocculation. The expression of the genes was several times higher in flocculent yeast cells than in powdery ones. Flow cytometry is a fast and simple method to quantify the proportions of powdery and flocculent yeast cells in suspensions under defined cultivation conditions. However, differentiation under industrial conditions will require mRNA and protein expression profiling.