ABSTRACT
Hydrogen sulfide (H2S) plays a vital role in Al3+ stress resistance in plants, but the underlying mechanism is unclear. In the present study, pretreatment with 2 µM of the H2S donor NaHS significantly alleviated the inhibition of root elongation caused by Al toxicity in rice roots, which was accompanied by a decrease in Al contents in root tips under 50 µM Al3+ treatment. NaHS pretreatment decreased the negative charge in cell walls by reducing the activity of pectin methylesterase and decreasing the pectin and hemicellulose contents in rice roots. This treatment also masked Al-binding sites in the cell wall by upregulating the expression of OsSATR1 and OsSTAR2 in roots and reduced Al binding in the cell wall by stimulating the expression of the citrate acid exudation gene OsFRDL4 and increasing the secretion of citrate acid. In addition, NaHS pretreatment decreased the symplasmic Al content by downregulating the expression of OsNRAT1, and increasing the translocation of cytoplasmic Al to the vacuole via upregulating the expression of OsALS1. The increment of antioxidant enzyme [superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD)] activity with NaHS pretreatment significantly decreased the MDA and H2O2 content in rice roots, thereby reducing the damage of Al3+ toxicity on membrane integrity in rice. H2S exhibits crosstalk with nitric oxide (NO) in response to Al toxicity, and through reducing NO content in root tips to alleviate Al toxicity. Together, this study establishes that H2S alleviates Al toxicity by decreasing the Al content in the apoplast and symplast of rice roots.
ABSTRACT
BACKGROUND: This study was designed to determine the molecular function of miR-141 and the underlying mechanisms in colorectal cancer (CRC). MATERIALS AND METHODS: SW480 cells in which miR-141 was up- or down-regulated were established. Reverse transcription, quantitative polymerase chain reaction and Western blotting were used to examine the microRNA and protein expression. Cell-cycle progression was analyzed by flow cytometry. Proliferation marker Ki-67 was evaluated by immunofluorescence. Transwell assay was conducted to determine the migration rates of cells. Subcutaneous xenograft models were used to examine the effect of miR-141 on tumorigenicity. Human mitogen-activated protein kinase (MAPK) and receptor tyrosine kinase (RTK) pathway phosphorylation array assays were used to interrogate MAPK and RTK pathway activation. RESULTS: miR-141 directly targeted zinc finger E-box-binding homeobox 1/2 (ZEB1/2). We first determined the expression levels of ZEB1 and ZEB2 in miR-141-expressing cells and miR-141-knockdown cells and found that inhibition of miR-141 significantly increased the expression of ZEB2. In vitro study revealed that miR-141 overexpression inhibited the expression of Ki-67. Furthermore, overexpression of miR-141 led to a significant reduction in the proliferation of SW480 cells via induction of cell-cycle arrest at the G1 stage. In contrast, inhibition of miR-141 markedly promoted the proliferation of SW480 cells by promoting cell-cycle progression. Moreover, overexpression of miR-141 significantly inhibited SW480 cell migration in vitro. In addition, overexpression of miR-141 significantly reduced tumor size and weight, and inhibited the growth of SW480 cell-derived tumor in nude mice. Notably, overexpression of miR-141 also suppressed the liver metastasis of SW480 cells in nude mice. Using RTK and MAPK arrays, we found increased phosphorylation of hepatocyte growth factor receptor (HGFR/c-MET) following inhibition of miR-141, but phosphorylation of P53, AKT, ERK1/2, P38 and mTOR, etc., in SW480 cells was not affected by miR-141. CONCLUSION: Our results suggest that miR-141 functions as a tumor suppressor through ZEB2 and HGFR in CRC cells.
