Plants can successfully improve their resistance to previously lethal salinity stress by a short exposure to low levels of salt stress, a process known as salt acclimation (SA). In spite of its fundamental significance in theoretical study and agricultural practice, the molecular mechanisms underlying plant SA remain elusive. In this study, we found that salt acclimated Arabidopsis young seedlings can survive subsequent 200 mM NaCl stress. RNA-seq was performed to analyze the genome-wide transcriptional response under SA conditions. Among 518 differentially expressed genes (DEGs) under SA, 366 up-regulated genes were enriched for cell wall biosynthesis, osmoregulation, oxidative stress, or transcription factors. Seven DEGs participate in the synthesis of lignin and 24 DEGs encode plant cell wall proteins, suggesting the importance of cell wall remodeling under SA. Furthermore, in comparison to non-acclimated salt stress, 228 of 245 DEGs were repressed by acclimated salt stress, including many genes related to ethylene biosynthesis and signaling pathway. In addition, MAPK6, a major component of the ethylene signaling pathway, was found to play a crucial role in SA. Our transcriptomic analysis has provided important insight on the roles of transcription factors, cell wall remodeling, and the ethylene biosynthesis and signaling pathways during SA in Arabidopsis.

Carbonic anhydrase (CA; EC 4.2.1.1) catalyzes the interconversion of CO 2 and HCO 3 − and plays an important role in photosynthetic carbon assimilation. We report that the effect of manipulating AtβCA6 expression on the growth and biomass accumulation of Arabidopsis thaliana shows that AtβCA6 was expressed in mitochondria. Overexpression of AtβCA6 increased the fresh weight, dry weight and rosette leaf area and it was also linked to a slight decrease in the rate of respiration. By contrast, when the respiration rate in the AtβCA6 knock-out mutant SALK_065611 increased, the fresh weight, dry weight and rosette leaf area decreased. The expression level of AtβCA6 mainly affected the expression of the genes that were related to metabolism, photosynthesis and respiration. We discuss these data with respect to a potential role of AtβCA6 in refixation of CO 2 released from respiration and its potential as an option to increase biomass production.

Salt stress is an important environmental factor limiting plant growth and crop production. Plant adaptation to salt stress can be improved by chemical pretreatment. This study aims to identify whether hydrogen peroxide (H2O2) pretreatment of seedlings affects the stress tolerance of Arabidopsis thaliana seedlings. The results show that pretreatment with H2O2 at appropriate concentrations enhances the salt tolerance ability of Arabidopsis seedlings, as revealed by lower Na+ levels, greater K+ levels, and improved K+/Na+ ratios in leaves. Furthermore, H2O2 pretreatment improves the membrane properties by reducing the relative membrane permeability (RMP) and malonaldehyde (MDA) content in addition to improving the activities of antioxidant enzymes, including superoxide dismutase, and glutathione peroxidase. Our transcription data show that exogenous H2O2 pretreatment leads to the induced expression of cell cycle, redox regulation, and cell wall organization-related genes in Arabidopsis, which may accelerate cell proliferation, enhance tolerance to osmotic stress, maintain the redox balance, and remodel the cell walls of plants in subsequent high-salt environments.

ADP-ribose-1′′-monophosphatase containing A1pp or MACRO domain is an important processing enzyme in cells, participating in splicing the t-RNA procedures and catalyzing ADP-ribose-1′′-monophosphate into ADP-ribose. We identified two genes, AT1G69340 and AT2G40600, in Arabidopsis thaliana and found that, although there were many differences in amino acid, the spatial structure of conserved region was similar. We also analyzed the difference in sequence of promoter, coding region and untranslated region using the data from the whole genome of 19 ecotypes and compared both genes' expression in different tissues in Col-0 and in seedlings in 19 ecotypes based on AtGenExpress database and the RNA-seq data, respectively. We found the same gene had different expression patterns in some ecotypes and the two genes had the similar expression patterns except in floral organs and seeds according to the data of Col-0. These results implied that the regulatory mechanisms of these genes' expressions had changed in these ecotypes for the diversities of transcription factors and transcription factor binding sites. Above all, our research will provide some information for description of the gene function and the ecotype candidates used to study the genes' function.