Overexpression of transcription factor SlWRKY28 improved the tolerance of Populus davidiana × P. bolleana to alkaline salt stress.

BACKGROUND: WRKY transcription factors (TFs) have been suggested to play crucial roles in the response to biotic and abiotic stresses. This study is the first to report the alkaline salt regulation of the WRKY gene. RESULTS: In this study, we cloned a WRKY gene (SlWRKY28) from the Salix linearistipularis and then transferred to the Populus davidiana × P. bolleana for expression. Sequence analysis on the transcriptome of Salix linearistipular showed the significant up-regulation of WRKY gene expression in response to salt-alkali stress in seedlings. Our data showed that SlWRKY28 localized to the nucleus. Furthermore, the expression of the SlWRKY28 from female plants increased with saline-alkali stress according to the northern blot analysis results. The results of 3,3'-Diaminobenzidine (DAB) staining showed that hydrogen peroxide (H2O2) concentration was lower under stress, but ascorbate peroxidase (APX) enzyme activity was significantly higher in the overexpressed plants than that in non-transgenic (NT) plants. CONCLUSIONS: We found out the SlWRKY28 induced regulation of the enzyme gene in the reactive oxygen species (ROS) scavenging pathway is a potential mechanism for transgenic lines to improve their resistance to alkaline salt. This study shows theoretical and practical significance in determining SlWRKY28 transcription factors involved in the regulation of alkaline salt tolerance.

De novo assembly of Amorpha fruticosa L. transcriptome in response to drought stress provides insight into the tolerance mechanisms.

BACKGROUND: Amorpha fruticosa L. is a deciduous shrub that is native to North America and has been introduced to China as an ornamental plant. In order to clarify the drought resistance characteristics of Amorpha fruticosa L. and excavate the related genes involved in drought resistance regulation pathway, the mechanism of drought resistance stress of Amorpha fruticosa L. was revealed by the changes of transcriptome of Amorpha fruticosa L. under drought stress.Through the changes of the transcriptome of Amorpha fruticosa L. under drought stress, the mechanism of anti-stress of Amorpha fruticosa L. could be revealed. METHODS: Different concentrations of polyethylene glycol-6000 (PEG-6000) was used to simulate drought stress, and transcriptomic analysis was used to reveal the changes of gene expression patterns in Amorpha fruticosa L. seedlings. RESULTS: Results showed that Amorpha fruticosa L. seedlings were seriously affected by PEG-6000. As for the differently expressed genes (DEGs), most of them were up-regulated. The additional Go and KEGG analysis results showed that DEGs were functionally enriched in cell wall, signal transduction and hormonal regulation related pathways. DEGs like AfSOD, AfHSP, AfTGA, AfbZIP and AfGRX play roles in response to drought stress. CONCLUSION: In conclusion, Amorpha fruticosa L. seedlings were sensitive to drought, which was different from Amorpha fruticosa L. tree, and the genes functions in drought stress responses via ABA-independent pathways. The up-regulation of Salicylic acid signal related DEGs (AfTGA and AfPR-1) indicated that Salicylic acid play a key role in response to drought stress in Amorpha fruticosa L.

Isolation and identification of a halophilic and alkaliphilic microalgal strain.

Halophilic and alkaliphilic microalgal strain SAE1 was isolated from the saline-alkaline soil of Songnen Plain of Northeast China. Morphological observation revealed that SAE1 has a simple cellular structure, single cell, spherical, diameter of four to six µm, cell wall of about 0.22 µm thick, two chloroplasts and one nucleus. Analysis of the phylogenetic tree constructed by 18S sequence homology suggests that SAE1 is highly homologous to Nannochloris sp. BLD-15, with only four base substitutions in the homologous region. SAE1 was initially considered as Nannochloris sp. Analysis of the halophilic and alkaliphilic characteristics of SAE1 indicates that it can grow under one M NaHCO3 and NaCl concentrations, with optimal growth under 400 mM NaHCO3 and 200 mM NaCl. The intracellular ultrastructure of SAE1 significantly changed after NaCl and NaHCO3 treatments. A large number of starch grains accumulated after treatment with 400 mM NaHCO3 in cells, but few were found after treatment with 200 mM NaCl and none in the living condition without treatment. We conjectured that one of the metabolic characteristics of alkaliphilic (NaHCO3) microalga SAE1 is the formation of massive starch grains, which induce glycerol anabolism and increase osmotic pressure, thereby enhancing its ability to resist saline-sodic conditions. This feature of alkaliphilic (NaHCO3) microalga SAE1 contributes to its growth in the carbonate soil of Songnen Plain.