Plant growth-promoting and antibacterial activities of cultivable bacteria alive in tobacco field against Ralstonia solanacearum.

Bacterial wilt disease caused by Ralstonia solanacearum leads to decrease of crops yield. Investigation of cultivable bacteria diversity provides more microbial species for screening antagonistic bacteria. In the present study, a variety of cultivation methods were used to investigate the diversity of cultivable bacteria alive in tobacco field. A total of 441 bacterial strains were obtained that belonged to four phyla, 49 genera and 146 species. Actinobacteria and Proteobacteria were the dominant phyla. Agrobacterium, Arthrobacter, Bacillus, Klebsiella, Paenarthrobacter, Pseudomonas and Pseudarthrobacter were the dominant genera. Some rare genera were discovered including Bosea, Cedecea, Delftia and Dyella. Diversity, species and abundances of bacteria altered under different cultivation conditions. One hundred three bacterial strains showed plant growth-promoting attributes. Twenty Bacillus strains showed high antibacterial activity against R. solanacearum. In field experiments, individual strain and consortia of Bacillus subtilis, B. siamensis and B. vallismortis effectively inhibited bacterial wilt. The core genes that controlled synthesis of secondary metabolites were knocked out in B. vallismortis SSB-10. Difficidin, which was synthesized by dif operon and controlled by sfp gene, was the antibacterial substance produced by SSB-10. Difficidin destroyed cell wall and cell membrane of R. solanacearum and inhibited its motility, production of extracellular polysaccharides and cellulase activity.

Proteomic identification of OsCYP2, a rice cyclophilin that confers salt tolerance in rice (Oryza sativa L.) seedlings when overexpressed.

BACKGROUND: High Salinity is a major environmental stress influencing growth and development of rice. Comparative proteomic analysis of hybrid rice shoot proteins from Shanyou 10 seedlings, a salt-tolerant hybrid variety, and Liangyoupeijiu seedlings, a salt-sensitive hybrid variety, was performed to identify new components involved in salt-stress signaling. RESULTS: Phenotypic analysis of one protein that was upregulated during salt-induced stress, cyclophilin 2 (OsCYP2), indicated that OsCYP2 transgenic rice seedlings had better tolerance to salt stress than did wild-type seedlings. Interestingly, wild-type seedlings exhibited a marked reduction in maximal photochemical efficiency under salt stress, whereas no such change was observed for OsCYP2-transgenic seedlings. OsCYP2-transgenic seedlings had lower levels of lipid peroxidation products and higher activities of antioxidant enzymes than wild-type seedlings. Spatiotemporal expression analysis of OsCYP2 showed that it could be induced by salt stress in both Shanyou 10 and Liangyoupeijiu seedlings, but Shanyou 10 seedlings showed higher OsCYP2 expression levels. Moreover, circadian rhythm expression of OsCYP2 in Shanyou 10 seedlings occurred earlier than in Liangyoupeijiu seedlings. Treatment with PEG, heat, or ABA induced OsCYP2 expression in Shanyou 10 seedlings but inhibited its expression in Liangyoupeijiu seedlings. Cold stress inhibited OsCYP2 expression in Shanyou 10 and Liangyoupeijiu seedlings. In addition, OsCYP2 was strongly expressed in shoots but rarely in roots in two rice hybrid varieties. CONCLUSIONS: Together, these data suggest that OsCYP2 may act as a key regulator that controls ROS level by modulating activities of antioxidant enzymes at translation level. OsCYP2 expression is not only induced by salt stress, but also regulated by circadian rhythm. Moreover, OsCYP2 is also likely to act as a key component that is involved in signal pathways of other types of stresses-PEG, heat, cold, or ABA.

[Advances in plant proteomics. II. Application of proteome techniques to plant biology research].

Proteome techniques have widely been applied to the fields of plant genetics, plant development, and plant physiology and ecology to investigate plant genetic diversity, plant development such as seed maturation and germination processes, differentiation of plant tissue and organ, separation and functional identification of novel component of various organells, mechanisms of plant adapted to abiotic or biotic stresses including high temperature, low temperature, high salt, drought, and pathogens and insects, and interaction of plant with microbe. The prospects of plant proteomics are discussed.

[Advances in plant proteomics--I. Key techniques of proteome].

With the completion of genome sequences of the model plants, such as rice (Oryza sativa L.) and Arabidopsis thaliana, it has come into plant functional genomics era, which becomes a hard base of the appearance and development of plant proteomics. This review focuses on the background of proteomics, concept of proteomics and key techniques of proteomics. The key techniques of proteomics include separation, such as 2-DE (Two-Dimensional Electrophoresis), RP-HPLC (Reverse Phase High Performance Liquid Chromatography) and SELDI (Surface Enhanced Laser Desorption/ Ionization) protein chip, mass spectrometry, such as MALDI-TOF-MS (Matrix Assisted Laser Desorption/Ionization-Time Of Flight-Mass Spectrometry) and ESI-MS/MS (Electrospray Ionization Mass Spectrometry/Mass Spectrometry), databases related to proteomics, quantitative proteome, TAP (Tandem Affinity Purification) and yeast two-hybrid system. Challenges and prospects of proteomic techniques are discussed.