Generation of tobacco lines with widely different reduction in nicotine levels via RNA silencing approaches.

Issues related to the nicotine content of tobacco have been public concerns.Several reports have described decreasing nicotine levels by silencing the putrescine N-methyltransferase (PMT) genes, but the reported variations of nicotine levels among transgenic lines are relatively low in general. Here we describe the generation in tobacco (Nicotiana tabacum) lines with widely different, reduced nicotine levels using three kinds of RNA-silencing approaches.The relative efficacies of suppression were compared among the three approaches regarding the aspect of nicotine level in tobacco leaves.By suppressing expression of the PMT genes, over 200 transgenic lines were obtained with nicotine levels reduced by 9.1-96.7%. RNA interference (RNAi) was the most efficient method of reducing the levels of nicotine,whereas cosuppression and antisense methods were less effective. This report gives clues to the efficient generation of plants with a variety of metabolite levels, and the results demonstrate the relative efficiencies of various RNA-silencing methods.

Isolation and characterization of a new mannose-binding lectin gene from Taxus media.

In this paper, we report the cloning and characterization of the first mannose-binding lectin gene from a gymnosperm plant species, Taxus media. The full-length cDNA of T. media agglutinin (TMA) consisted of 676 bp and contained a 432 bp open reading frame (ORF) encoding a 144 amino acid protein. Comparative analysis showed that TMA had high homology with many previously reported plant mannose-binding lectins and that tma encoded a precursor lectin with a 26-aa signal peptide. Molecular modelling revealed that TMA was a new mannosebinding lectin with three typical mannose-binding boxes like lectins from species of angiosperms. Tissue expression pattern analyses revealed that tma is expressed in a tissue-specific manner in leaves and stems, but not in fruits and roots. Phylogenetic tree analyses showed that TMA belonged to the structurally and evolutionarily closely related monocot mannose-binding lectin superfamily. This study provides useful information to understand the molecular evolution of plant lectins.