[Atrazine changes meiosis and reduces spermatogenesis in male mice].

OBJECTIVE: To investigate the effects of exposure to atrazine on meiosis and spermatogenesis in adult male mice. METHODS: We divided 16 adult male Institute for Cancer Research (ICR) mice into a solvent control and an atrazine exposure group of an equal number and intraperitoneally injected with solvent dimethylsulfoxide (DMSO) and atrazine at 100 mg/kg/d, respectively. After 4 weeks of treatment, we obtained the body and testis weights of the mice, observed the changes in the testicular histomorphology, examined the cell apoptosis in the testis tissue, and determined the expressions of meiosis-related key genes in the spermatocytes by real-time fluorescence quantitative PCR. RESULTS: Compared with the controls, the mice treated with atrazine showed significantly less increase in the body weight (ï¼»11.2 ± 0.17ï¼½ vs ï¼»8.29 ± 0.51ï¼½ g, P < 0.05) and testis weight (ï¼»0.28 ± 0.01ï¼½ vs ï¼»0.24 ± 0.01ï¼½ g, P < 0.05), loosely arranged and thinned lumens of seminiferous tubules, disordered arrangement and reduced number of spermatogenic cells, decreased sperm concentration (ï¼»2.36 ± 0.14ï¼½ vs ï¼»0.90 ± 0.12ï¼½ ×106/ml, P < 0.01) and increased percentage of morphologically abnormal sperm in the epididymis tail (ï¼»8.60 ± 1.07ï¼½% vs ï¼»18.02 ± 1.71ï¼½%, P < 0.05), elevated apoptosis rate of spermatocytes, and down-regulated the expressions of SCP1, SCP3 and Rad51 mRNA in the spermatocytes (P < 0.05). CONCLUSIONS: Atrazine can reduce spermatogenesis in male mice by damaging testicular morphology, increasing the apoptosis of spermatocytes and down-regulating the expressions of meiosis-related genes in the spermatocytes.

Structure of a plant ß-galactosidase C-terminal domain.

Most plant ß-galactosidases, which belong to glycoside hydrolase family 35, have a C-terminal domain homologous to animal galactose and rhamnose-binding lectins. To investigate the structure and function of this domain, the C-terminal domain of the rice (Oryza sativa L.) ß-galactosidase 1 (OsBGal1 Cter) was expressed in Escherichia coli and purified to homogeneity. The free OsBGal1 Cter is monomeric with a native molecular weight of 15kDa. NMR spectroscopy indicated that OsBGal1 Cter comprises five ß-strands and one α-helix. The structure of this domain is similar to lectin domains from animals, but loops A and C of OsBGal1 Cter are longer than the corresponding loops from related animal lectins with known structures. In addition, loop A of OsBGal1 Cter was not well defined, suggesting it is flexible. Although OsBGal1 Cter was predicted to be a galactose/rhamnose-binding domain, binding with rhamnose, galactose, glucose, ß-1,4-d-galactobiose and raffinose could not be observed in NMR experiments.

Rice Os9BGlu31 is a transglucosidase with the capacity to equilibrate phenylpropanoid, flavonoid, and phytohormone glycoconjugates.

Glycosylation is an important mechanism of controlling the reactivities and bioactivities of plant secondary metabolites and phytohormones. Rice (Oryza sativa) Os9BGlu31 is a glycoside hydrolase family GH1 transglycosidase that acts to transfer glucose between phenolic acids, phytohormones, and flavonoids. The highest activity was observed with the donors feruloyl-glucose, 4-coumaroyl-glucose, and sinapoyl-glucose, which are known to serve as donors in acyl and glucosyl transfer reactions in the vacuole, where Os9BGlu31 is localized. The free acids of these compounds also served as the best acceptors, suggesting that Os9BGlu31 may equilibrate the levels of phenolic acids and carboxylated phytohormones and their glucoconjugates. The Os9BGlu31 gene is most highly expressed in senescing flag leaf and developing seed and is induced in rice seedlings in response to drought stress and treatment with phytohormones, including abscisic acid, ethephon, methyljasmonate, 2,4-dichlorophenoxyacetic acid, and kinetin. Although site-directed mutagenesis of Os9BGlu31 indicated a function for the putative catalytic acid/base (Glu(169)), catalytic nucleophile residues (Glu(387)), and His(386), the wild type enzyme displays an unusual lack of inhibition by mechanism-based inhibitors of GH1 ß-glucosidases that utilize a double displacement retaining mechanism.