Duckweed (Lemna minor) is a novel natural inducer of cellulase production in Trichoderma reesei.

An inducer is crucial for cellulase production. In this study, duckweed was used as an inducer of cellulase production by Trichoderma reesei RUT C30. In a reaction induced by 50 g/L duckweed in shake flasks, the filter-paper activity (FPA) reached 6.5 FPU/mL, a value comparable to that induced by avicel. The enzyme-hydrolysis rate induced by steam-exploded corn stalk was 54.2%, representing a 28% improvement over that induced by avicel. The duckweed starch was hydrolyzed to glucose, which was subsequently used for biomass accumulation during the fermentation process. Furthermore, to optimize the control of the fermentation process, a combined substrate of avicel and duckweed was used to induce cellulase production by T. reesei RUT C30. The cellulase production and hydrolysis rates of the combined substrate, compared with avicel alone, were 39.6% and 36.7% higher, respectively. The results of this study suggest that duckweed is a good inducer of cellulase production in T. reesei, and it might aid in decreasing the cost of lignocellulosic materials hydrolysis.

Ecological functions and differentially expressed transcripts of translucent bracts in an alpine 'glasshouse' plant Rheum nobile (Polygonaceae).

The molecular basis of many physiological and/or phenotypic adaptations of alpine plants remains largely unknown. The upper leaves of what are termed "glasshouse plants" have been transformed into translucent bracts that cover their inflorescences. This change in appearance is believed to allow such plants to maintain normal sexual reproduction under very cold conditions. Thus, it is hypothesized that the foliar roles of these bracts have been altered as an adaptation to alpine environments. In the present study, a test of this hypothesis revealed distinct physiological and anatomical differences (especially related to photosynthesis) between the bracts and normal leaves in one 'glasshouse' species, Rheum nobile Hook. f. and Thomson. A cDNA-AFLP analysis, was conducted to identify candidate genes involving differential expression in bracts and normal leaves, detected 323 (5.4%) transcript-derived fragments (TDFs) that were differentially expressed (up- or down-regulated) among 6,000 TDFs recovered. In total, 110 differentially expressed TDFs were sequenced, of which 52 were homologous to genes reported from other plants. More than half of the candidate genes represented by the unidentified TDFs may be specific to the Rheum lineage or have arisen through adaptive processes in alpine plants. All putative genes involved in photosynthesis had been down-regulated, while those related to stress and defense response were up-regulated in the bracts. These differentially expressed genes are highly congruent with physiological and anatomical differences between the bracts and normal leaves, indicating that they are associated with functions that confer a physiological advantage in alpine conditions.