Phytomelatonin is a universal signal molecule that regulates plant growth and stress response. However, only one receptor, AtPMTR1/CAND2 that could directly bind with and perceive melatonin signaling has been identified in dicotyledon plant Arabidopsis so far, whether other plants contain phytomelatonin receptor and how it functions are still unknown. Herein, we identified a new phytomelatonin receptor from monocot maize, and investigated its role in plant osmotic and drought stress response. Using homology searching, maize plasma membrane-localized Zm00001d034063/ZmPMTR1 protein with strong binding activity to melatonin was identified as a potential phytomelatonin receptor in maize. Overexpressing ZmPMTR1 promoted osmotic stress tolerance of the wild-type Arabidopsis plant, and rescued osmotic stress sensitivity of the Arabidopsis cand2-1 mutant. Moreover, ZmPMTR1 largely rescued defect of melatonin-induced stomatal closure in the cand2-1 mutant, thereby reducing water loss rate and increasing drought stress tolerance. Furthermore, we identified a maize mutant of ZmPMTR1, EMS4-06e2fl with a point mutation causing premature termination of protein translation, and found that this maize mutant had lower leaf temperature, increased water loss rate and enhanced drought stress sensitivity. Collectively, our study reveals that ZmPMTR1, as the first identified and analyzed phytomelatonin receptor in monocot plant, functions necessarily in maize plant drought stress tolerance.
Epigallocatechin
gallate (EGCG) has been regarded as a protective
bioactive polyphenol in green tea against nonalcoholic steatohepatitis
(NASH), but the mechanism remains poorly deciphered. Herein, we assessed
the role and mechanism of EGCG on gut microbiota and the metabolism
in NASH development. Forty-eight male C57BL/6J mice were fed with
either a methionine–choline-sufficient diet or a methionine–choline-deficient
(MCD) diet with or without EGCG administration for 4 weeks. Liver
injury, inflammation, lipid accumulation, and iron overload were examined.
16S ribosomal RNA sequencing was used to detect the fecal microbiome.
In our research, we observed that EGCG notably improved MCD-diet-derived
gut microbiota dysbiosis, as proved by a distinctively clustered separation
from that of the MCD group and by the decrease of the
Oxalobacter
,
Oscillibacter
,
Coprococcus_1,
and
Desulfovibrio
genera and enrichment of
norank_f__Bacteroidales_S24_7_group
,
Alloprevotella
, and
Bacteroides
. Spearman-correlation heatmap analysis
indicated that
Bacteroides
and
Alloprevotella
induced by EGCG were strongly negatively
correlated with lipid accumulation. Functional enzymes of the gut
microbiome were predicted by PICRUSt based on the operation classification
unit. The results revealed that 1468 enzymes were involved in various
metabolic pathways, and 371 enzymes showed distinct changes between
untreated and EGCG-treated mice. Long-chain-fatty-acid-CoA ligase
ACSBG played a distinct role in fatty acid metabolism and ferroptosis
and was significantly negatively correlated with
Bacteroides
. Altogether, the salutary effect of EGCG on NASH might be via shifting
gut flora and certain enzymes from genera. Our study thus takes a
step toward NASH prevention and therapy.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Osmotic stress severely inhibits plant growth and development, causing huge loss of crop quality and quantity worldwide. Melatonin is an important signaling molecule that generally confers plant increased tolerance to various environmental stresses, however, whether and how melatonin participates in plant osmotic stress response remain elusive. Here, we report that melatonin enhances plant osmotic stress tolerance through increasing ROS-scavenging ability, and melatonin receptor CAND2 plays a key role in melatonin-mediated plant response to osmotic stress. Upon osmotic stress treatment, the expression of melatonin biosynthetic genes including SNAT1, COMT1, and ASMT1 and the accumulation of melatonin are increased in the wild-type plants. The snat1 mutant is defective in osmotic stress-induced melatonin accumulation and thus sensitive to osmotic stress, while exogenous melatonin enhances the tolerance of the wild-type plant and rescues the sensitivity of the snat1 mutant to osmotic stress by upregulating the expression and activity of catalase and superoxide dismutase to repress H2O2 accumulation. Further study showed that the melatonin receptor mutant cand2 exhibits reduced osmotic stress tolerance with increased ROS accumulation, but exogenous melatonin cannot revert its osmotic stress phenotype. Together, our study reveals that CADN2 functions necessarily in melatonin-conferred osmotic stress tolerance by activating ROS-scavenging ability in Arabidopsis.
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