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Histone modification is an important epigenetic regulation in higher plants adapting to environment changes including salt and drought stresses. In this report, we show that the Arabidopsis RPD3-type histone deacetylase HDA9 is involved in modulating plant responses to salt and drought stresses in Arabidopsis. Loss-of-function mutants of the gene displayed phenotypes (such as seedling root growth and seed germination) insensitive to NaCl and polyethylene glycol (PEG) treatments. HDA9 mutation led to up-regulation of many genes, among which those involved in response to water deprivation stress (GO: 0009414) were enriched. These genes were much more induced in the mutants than wild-type plants when treated with PEG and NaCl. In addition, we found that in the mutants, salt and drought stresses led to much higher levels of histone H3K9 acetylation at promoters of 14 genes randomly selected from those that respond to water-deprivation stress than in wild-type plants. Our study suggested that HDA9 might be a novel chromatin protein that negatively regulates plant sensitivity to salt and drought stresses by regulating histone acetylation levels of a large number of stress-responsive genes in Arabidopsis.

Exosomes, a group of vesicles originating from the multivesicular bodies (MVBs), are released into the extracellular space when MVBs fuse with the plasma membrane. Numerous studies indicate that exosomes play important roles in cell-to-cell communication, and exosomes from specific cell types and conditions display multiple functions such as exerting positive effects on regeneration in many tissues. It is widely accepted that the therapeutic potential of stem cells may be mediated largely by the paracrine factors, so harnessing the paracrine effects of stem and progenitor cells without affecting these living, replicating, and potentially pluripotent cell populations is an advantage in terms of safety and complexity. Ascending evidence indicated that exosomes might be the main components of paracrine factors; thus, understanding the role of exosomes in each subtype of stem cells is far-reaching. In this review, we discuss the functions of exosomes from different types of stem cells and emphasize the therapeutic potentials of exosomes, providing an alternative way of developing strategies to cure diseases.

Background MicroRNAs (miRNAs) are implicated in the progression of ischemic stroke (IS) and bone marrow-derived mesenchymal stem cells (BMSCs)-derived exosomes play a role in IS therapy. Herein we hypothesized that the BMSCs-derived exosomes containing overexpressed miR-138-5p could protect the astrocytes following IS involved with lipocalin 2 (LCN2). Methods The differentially expressed gene related to IS was initially identified by bioinformatics analysis. miR-138-5p was predicted to regulate LCN2. The expression of miR-138-5p and LCN2 was altered in the oxygen-glucose deprivation (OGD)-induced astrocytes. Furthermore, the cell behaviors and inflammatory responses were evaluated both in astrocytes alone and astrocytes co-cultured with exosomes derived from BMSCs overexpressing miR-138-5p to explore the involvement of miR-138-5p and LCN2 in IS. Besides, middle cerebral artery occlusion (MCAO) mouse model was established to explore the effect of BMSCs-derived exosomal miR-138-5p in IS in vivo. Results LCN2 was highly expressed in IS. Besides, LCN2 was a target gene of miR-138-5p. BMSCs-derived exosomes could be endocytosed by astrocytes via co-culture. Overexpression of miR-138-5p promoted the proliferation and inhibited apoptosis of astrocytes injured by OGD, accompanied by the reduced expression of inflammatory factors, which was achieved by down-regulating LCN2. More importantly, BMSCs delivered miR-138-5p to the astrocytes via exosomes and BMSCs-derived exosomal miR-138-5p alleviated neuron injury in IS mice. Conclusion BMSCs-derived exosomal miR-138-5p reduces neurological impairment by promoting proliferation and inhibiting inflammatory responses of astrocytes following IS by targeting LCN2, which may provide a novel target for IS treatment.