Zheng Xiaobo

Mammalian pro-apoptotic bax gene enhances tobacco resistance to pathogens

Emerging evidence suggests that plants and animals may share certain biochemical commonalities in apoptosis, or programmed cell death (PCD) pathways, though plants lack key animal apoptosis related genes. In plants, PCD has many important functions including a role in immunity and resistance to pathogen infection. In this study, a rice phenylalanine ammonia-lyase promoter is used to regulate the expression of the mouse pro-apoptotic bax gene in transgenic tobacco plants. Ectopic expression of the bax negatively affects the growth of transgenic plants. Nonetheless, results show that the bax transgene is induced upon infection by plant pathogens and accumulation of Bax is observed by Western blot analysis. By estimating and measuring the extent of cell death, release of active oxygen species, and accumulation defense-associated gene transcripts, it is shown that bax transgenic plants mount a more robust cell death response compared to control plants. The bax transgenic tobacco plants are also more resistant to infection by Phytophthoraparasitica and Ralstoniasolanacearum, but have no obvious resistance to tobacco mosaic virus. These results substantiate past studies and illustrate the powerful effects mammalian bax genes may have on plant development and disease resistance.Emerging evidence suggests that plants and animals may share certain biochemical commonalities in apoptosis, or programmed cell death (PCD) pathways, though plants lack key animal apoptosis related genes. In plants, PCD has many important functions including a role in immunity and resistance to pathogen infection. In this study, a rice phenylalanine ammonia-lyase promoter is used to regulate the expression of the mouse pro-apoptotic bax gene in transgenic tobacco plants. Ectopic expression of the bax negatively affects the growth of transgenic plants. Nonetheless, results show that the bax transgene is induced upon infection by plant pathogens and accumulation of Bax is observed by Western blot analysis. By estimating and measuring the extent of cell death, release of active oxygen species, and accumulation defense-associated gene transcripts, it is shown that bax transgenic plants mount a more robust cell death response compared to control plants. The bax transgenic tobacco plants are also more resistant to infection by Phytophthora parasitica and Ralstonia solanacearum, but have no obvious resistance to tobacco mosaic virus. These results substantiate past studies and illustrate the powerful effects mammalian bax genes may have on plant development and disease resistance.

A Phytophthora sojae gene of glyceraldehyde-3-phosphate dehydrogenase （GAPDH） induced in host infection and its anti-oxidative function in yeast

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional protein well defined in eukaryotes, especially in mammalian and Saccharomyces cerevisiae. Using the method of suppression subtractive hybridization (SSH), we identified a Phytophthora sojae cDNA coding GAPDH, which was up-regulated during the early stage of soybean infection. The termed PsGapdh gene possessed three copies in the P. sojae genome. Its amino acid sequence harbored overall conserved domain of GADPH, homologous closest to GapC1 of Achlya bisexualis (oomycete) and adjoined to GapC2s of Odontella sinensis and Phaeodactylum tricornutum (diatom), on the C-II branch of subfamily GapC in phylogeny tree of GAPDH. The transcriptional level of PsGapdh was up-regulated throughout early infection. Heterogenous expression of PsGapdh in the yeast tdh1-deleted mutant could rescue growth arrest under continuous exposure to H2O2. These results indicated active roles of PsGapdh in pathogen-host interaction and anti-oxidation.

No significant differences in rhizosphere bacterial communities between Bt maize cultivar IE09S034 and the near-isogenic non-Bt cultivar Zong31

Liang J.G., Luan Y., Jiao Y., Xin L.T., Song X.Y., Zheng X.B., Zhang Z.G. (2018): No significant differences in rhizosphere bacterial communities between Bt maize cultivar IE09S034 and the near-isogenic non-Bt cultivar Zong31. Plant Soil Environ., 64: 427–434. The release of genetically modified (GM) crops has potential to alter the bacterial population within rhizosphere. Here, the potential effect of GM maize cv. IE09S034 containing the Cry1Ie toxin gene from Bacillus thuringiensis (Bt) was investigated under the field conditions. The community composition and the relative abundance of the bacteria in rhizosphere soil were estimated by analysing 16S rRNA PCR amplicons. Our results indicated that Bt maize IE09S034 has no significant effects on the rhizosphere bacterial community. Instead, it was found that factors such as plant growth stage and year have a stronger effect on the bacterial population dynamics. Our findings therefore provide reliable evidence supporting the potential commercial cultivation of the cv. IE09S034.

Screening and identification of mutants of Magnaporthe grisea by REMI

The plasmid pUCATPH was used to establish a transformation system in wild-type isolate M131 of Magnaporthe grisea. Six hundred and thirty-nine transformants were obtained by restriction enzyme-mediated integration (REMI) with hygromycin B (hyg B) resistance as a tag. Morphological analysis of two of the REMI mutants confirmed that they produced little melanin under black light and continued for three generations. Pathogenicity identification of six mutants screened proved that they made pathogenicity changes on three sets of differential varieties with different resistance genes. Rep-PCR analyses showed that two morphological mutants and two pathogenicity mutants differed from wild-type isolate M131 at the molecular level. RFLP analyses were performed to study the four mutants at the molecular level and the integration sites of the plasmid DNA. The results showed that the plasmid was inserted into all four mutants and that the insertion sites were random.