Catalytic promiscuity of rice 2-oxoglutarate/Fe(II)-dependent dioxygenases supports xenobiotic metabolism.

The rice (Oryza sativa) 2-oxoglutarate (2OG)/Fe(II)-dependent dioxygenase HIS1 mediates the catalytic inactivation of five distinct ß-triketone herbicides (bTHs). By assessing the effects of plant growth regulators on HIS1 enzyme function, we found that HIS1 mediates the hydroxylation of trinexapac-ethyl (TE) in the presence of Fe2+ and 2OG. TE blocks gibberellin biosynthesis, and we observed that its addition to culture medium induced growth retardation of rice seedlings in a concentration-dependent manner. Similar treatment with hydroxylated TE revealed that hydroxylation greatly attenuated the inhibitory effect of TE on plant growth. Forced expression of HIS1 in a rice his1 mutant also reduced its sensitivity to TE compared with that of the nontransformant. These results indicate that HIS1 metabolizes TE and thereby markedly reduces its ability to slow plant growth. Furthermore, analysis of five rice HIS1-like (HSL) proteins revealed that OsHSL2 and OsHSL4 also metabolize TE in vitro. HSLs from wheat (Triticum aestivum) and barley (Hordeum vulgare) also showed such activity. In contrast, OsHSL1, which shares the highest amino acid sequence identity with HIS1 and metabolizes the bTH tefuryltrione, did not manifest TE-metabolizing activity. Site-directed mutagenesis of OsHSL1 informed by structural models showed that substitution of three amino acids with the corresponding residues of HIS1 conferred TE-metabolizing activity similar to that of HIS1. Our results thus reveal a catalytic promiscuity of HIS1 and its related enzymes that support xenobiotic metabolism in plants.

Ciliated hepatic foregut cyst. A report of one case and a review of the literature.

We encountered a patient with a ciliated hepatic foregut cyst (CHFC), which is an uncommon cystic lesion of the liver and hard to distinguish from malignant tumor in imaging features. Cases of CHFC are very rare, five cases were reported in the 19th century and 53 cases in the 20th century. The histogenesis of CHFC is still unclear, but most authors consider that it could arise from the embryonic foregut. A few cases of CHFC mimicking neoplasm were reported. When the diagnosis of CHFC was obtained by fine needle aspiration, close follow-up is necessary in order to find early malignant change.