Cytoplasmic glutamine synthetase gene expression regulates larval development in Bactrocera dorsalis (Hendel).

In insects, glutamine synthetase (GS), a key enzyme in the synthesis of glutamine, has been reported to be associated with embryonic development, heat shock response, and fecundity regulation. However, little is known about the influence of GS on postembryonic development. In this study, we demonstrate that blocking the activity of GS in the oriental fruit fly (Bactrocera dorsalis) with use of a GS-specific inhibitor (L-methionine S-sulfoximine), led to a significant delay in larval development, pupal weight loss, and inhibition of pupation. We further identify cloned and characterized two GS genes (BdGS-c and BdGS-m) from B. dorsalis. The two GS genes identified in B. dorsalis were predicted to be located in the cytosol (BdGS-c) and mitochondria (BdGS-m), and homology analysis indicated that both genes were similar to homologs from other Dipterans, such as Drosophila melanogaster and Aedes aegypti. BdGS-c was highly expressed in the larval stages, suggesting that cytosolic GS plays a predominant role in larval development. Furthermore, RNA interference experiments against BdGS-c, to specifically decrease the expression of cytosolic GS, resulted in delay in larval development as well as pupal weight loss. This study presents the prominent role played by BdGS-c in regulating larval development and suggests that the observed effect could have been modulated through ecdysteroid synthesis, agreeing with the reduced expression of the halloween gene spook. Also, the direct effects of BdGS-c silencing on B. dorsalis, such as larval lethality, delayed pupation, and late emergence, can be further exploited as novel insecticide target in the context of pest management.

Four new minor taxanes from cell cultures of Taxus chinensis.

Four new minor taxanes (1-4) have been isolated from Ts-19 cell cultures of Taxus chinensis together with five known taxanes (5-9) by silica gel chromatography combined with semi-preparative HPLC chromatography. On the basis of the analyses of the chemical and spectroscopic (IR, MS, 1D, and 2D NMR) data, the structures of new compounds were elucidated as 5alpha-hydroxy-2alpha,10beta-diacetoxy-14beta-(3-hydroxy-2-methyl-butyryl)oxytaxa-4(20),11-diene (1), 2alpha,5alpha,10beta-triacetoxy-14beta-(2-hydroxy-propionyl)oxytaxa-4(20),11-diene (2), 2alpha,5alpha,10beta-triacetoxy-14beta-(2-hydroxy-3-methyl-butyryl)oxytaxa-4(20),11-diene (3), and 2alpha-benzoxy-4alpha,9alpha,10beta,13alpha-tetraacetoxytax-11-ene (4), respectively. Compounds 1-5 were pharmacologically evaluated for their cytotoxicities against five human cancer cell lines (HCT-8, Bel-7402, BGC-823, A549, and A2780) and their reversing activity towards multi-drug resistance A549/taxol tumor cell line, and the results showed that all of the tested compounds exhibited very low cytotoxicities, while compound 4 possessed twice the reversing activity as that of verapamil at 10 muM.