Identification of Chemicals That Abrogate Folate-Dependent Inhibition of Starch Accumulation in Non-Photosynthetic Plastids of Arabidopsis.

Folate, also known as vitamin B9, is an essential cofactor for a variety of enzymes and plays a crucial role in many biological processes. We previously reported that plastidial folate prevents starch biosynthesis triggered by the influx of sugar into non-starch-accumulating plastids, such as etioplasts, and chloroplasts under darkness; hence the loss of plastidial folate induces the accumulation of starch in plastids. To understand the molecular mechanism underlying this phenomenon, we screened our in-house chemical library and searched their derivatives to identify chemicals capable of inducing starch accumulation in etioplasts. The results revealed four chemicals, compounds #120 and #375 and their derivatives, compounds #120d and #375d, respectively. The derivative compounds induced starch accumulation in etioplasts and suppressed hypocotyl elongation in dark-grown Arabidopsis seedlings. They also inhibited the post-germinative growth of seedlings under illumination. All four chemicals contained the sulfonamide group as a consensus structure. The sulfonamide group is also found in sulfa drugs, which exhibit antifolate activity, and in sulfonylurea herbicides. Further analyses revealed that compound #375d induces starch accumulation by inhibiting folate biosynthesis. By contrast, compound #120d neither inhibited folate biosynthesis nor exhibited the herbicide activity. Protein and metabolite analyses suggest that compound #120d abrogates folate-dependent inhibition of starch accumulation in etioplasts by enhancing starch biosynthesis.

Visceral pleural perforation in two cases of ultrathin bronchoscopy.

Recently, ultrathin bronchoscopes with a thinner external diameter, greater visual range, improved visibility, and a larger working channel have been developed. The utility of a 2.8-mm diameter ultrathin bronchoscope in diagnosing peripheral pulmonary nodules has been reported by some authors. While the feasibility of approaching peripheral pulmonary lesions is attractive, peculiar complications that have not been experienced with standard bronchoscopy may occur. We report two cases in which pneumothoraces occurred because their visceral pleuras were perforated with an ultrathin bronchoscope during the procedure. The peculiar mechanism of pneumothorax in relation to ultrathin bronchoscopy is discussed.