Integrating transcriptome and metabolome to explore the growth-promoting mechanisms of GABA in blueberry plantlets.

Tissue culture technology is the main method for the commercial propagation of blueberry plants, but blueberry plantlets grow slowly and have long growth cycles under in vitro propagation, resulting in low propagation efficiency. In addition, the long culturing time can also result in reduced nutrient content in the culture medium, and the accumulation of toxic and harmful substances that can lead to weak growth for the plantlets or browning and vitrification, which ultimately can seriously reduce the quality of the plantlets. Gamma-aminobutyric acid (GABA) is a four-carbon non-protein amino acid that can improve plant resistance to various stresses and promote plant growth, but the effects of its application and mechanism in tissue culture are still unclear. In this study, the effects of GABA on the growth of in vitro blueberry plantlets were analyzed following the treatment of the plantlets with GABA. In addition, the GABA-treated plantlets were also subjected to a comparative transcriptomic and metabolomic analysis. The exogenous application of GABA significantly promoted growth and improved the quality of the blueberry plantlets. In total, 2,626 differentially expressed genes (DEGs) and 377 differentially accumulated metabolites (DAMs) were detected by comparison of the control and GABA-treated plantlets. Most of the DEGs and DAMs were involved in carbohydrate metabolism and biosynthesis of secondary metabolites. The comprehensive analysis results indicated that GABA may promote the growth of blueberry plantlets by promoting carbon metabolism and nitrogen assimilation, as well as increasing the accumulation of secondary metabolites such as flavonoids, steroids and terpenes.

Critical roles of the activation of ethylene pathway genes mediated by DNA demethylation in Arabidopsis hyperhydricity.

Hyperhydricity (HH) often occurs in plant tissue culture, seriously influencing the commercial micropropagation and genetic improvement. DNA methylation has been studied for its function in plant development and stress responses. However, its potential role in HH is unknown. In this study, we report the first comparative DNA methylome analysis of normal and hyperhydric Arabidopsis thaliana (L.) Heynh. seedlings using whole-genome bisulfite sequencing (BS-seq). We found that the global methylation level decreased in hyperhydric seedlings, and most of the differentially methylated genes were CHH hypomethylated genes. Moreover, the bisulfite sequencing results showed that hyperhydric seedlings displayed CHH demethylation patterns in the promoter of the ACS1 and ETR1 genes, resulting in upregulated expression of both genes and increased ethylene accumulation. Furthermore, hyperhydric seedling displayed reduced stomatal aperture accompanied by decreased water loss and increased phosphorylation of aquaporins accompanied by increased water uptake. While silver nitrate (AgNO3 ) prevented HH by maintained the degree of methylation in the promoter regions of ACS1 and ETR1 and downregulated the transcription of both genes. AgNO3 also reduced the content of ethylene together with the phosphorylation of aquaporins and water uptake. Taken together, this study suggested that DNA demethylation is a key switch that activates ethylene pathway genes to enable ethylene synthesis and signal transduction, which may subsequently influence aquaporin phosphorylation and stomatal aperture, eventually causing HH; thus, DNA demethylation plays a crucial role in HH. These results provide insights into the epigenetic regulation mechanism of HH and confirm the role of ethylene and AgNO3 in hyperhydricity control.

A systematic review and meta-analysis of risk factors in the conservative treatment of cesarean scar pregnancy.

BACKGROUND: It is important to investigate the risk factors of the failure of conservative treatment for cesarean scar pregnancy in order to improve the success rate of treatment and preserve the fertility of patients. This article aims to investigate these factors by meta-analysis, so as to serve as a clinical reference. METHODS: PubMed, MEDLINE, Embase, and the Cochrane Library databases were searched. Literatures related to the treatment of cesarean scar pregnancy (CSP) were selected. Literatures were screened according to the inclusion and exclusion criteria, and the quality was evaluated. RevMan 5.3.5 software was used to conduct the meta-analysis on the factors of treatment failure. RESULTS: A total of 7 articles were included in this study, involving 251 patients. Among them, there were 79 (31.5%) cases of conservative treatment failure. The results of the meta-analysis showed that more than 2 cesarean sections [OR =1.79, 95% CI: (0.94, 3.42), P=0.08], mass type CSP [OR =4.06, 95% CI: (2.11, 7.81), P<0.0001], serum ß-hCG value <20,000 U/L [OR =1.81, 95% CI: (0.92, 3.54), P=0.09], and pregnancy time over 3 years from last cesarean section [OR =4.12, 95% CI: (1.29, 13.08), P=0.02] were the risk factors for the failure of conservative treatment of CSP. DISCUSSION: A total of 7 studies were included in this meta-analysis. The results showed that more than 2 cesarean sections, mass type CSP, serum ß-hCG value <20,000 U/L, and pregnancy time over 3 years from last cesarean section were risk factors for the failure of conservative treatment of CSP. Patients with the above risk factors should be screened and informed of the possibility of conservative treatment failure in a timely manner, and different methods should be considered for treatment.

Phenotypic Analysis and Molecular Markers of Plant Nodule Senescence.

Leguminous crops can form nodules to fix atmospheric nitrogen (N2). Senescence of nodules is associated with a rapid decline in N fixation. During the process of nodule senescence, a number of visible or detectable changes on morphology, biochemistry, and physiology occur. Here we describe several methods for examining the senescing phenotypes of nodules, including rhizobium inoculation, nitrogenase activity determination with the acetylene reduction assay, leghemoglobin content determination, and apoptotic cell identification with TdT-mediated dUTP-biotin nick end-labeling (TUNEL) staining.

Reversion of hyperhydricity in pink (Dianthus chinensis L.) plantlets by AgNO3 and its associated mechanism during in vitro culture.

Hyperhydricity occurs frequently in plant tissue culture and can severely affect commercial micropropagation and genetic improvement of the cultured plantlets. Hyperhydric shoots are charaterzized by high water content, but how this occurs is still a subject of investigation. Silver ion (Ag+) can reduce the extent of hyperhydricity in plants, but its effect on the reversion of hyperhydric plantlets and the underlying mechanism of reversion has not been clarified. In this study, about 67% of the hyperhydric Dianthus chinensis L. plantlets were found to revert to normal condition when the plantlets were cultured in medium supplemented with 29.4µmolL-1AgNO3. Water content and hydrogen peroxide (H2O2) content in the guard cells of these plantlets were reduced, while stomatal aperture and water loss rate were increased. AgNO3 also reduced the content of endogenous ethylene and expression of ethylene synthesis and ethylene signal transduction-associated genes. Reduced accumulation of ethylene consequently led to an increase in stomatal aperture mediated by decreased H2O2 content in the guard cells. These results adequately verified the role of AgNO3 in the reversion of hyperhydricity in D. chinensis L. and also provided clues for exploring the cause of excessive water accumulation in hyperhydric plants.

An ABA-regulated and Golgi-localized protein phosphatase controls water loss during leaf senescence in Arabidopsis.

It is known that a senescing leaf loses water faster than a non-senescing leaf and that ABA has an important role in promoting leaf senescence. However, questions such as why water loss is faster, how water loss is regulated, and how ABA functions in leaf senescence are not well understood. Here we report on the identification and functional analysis of a leaf senescence associated gene called SAG113. The RNA blot and GUS reporter analyses all show that SAG113 is expressed in senescing leaves and is induced by ABA in Arabidopsis. The SAG113 expression levels are significantly reduced in aba2 and abi4 mutants. A GFP fusion protein analysis revealed that SAG113 protein is localized in the Golgi apparatus. SAG113 encodes a protein phosphatase that belongs to the PP2C family and is able to functionally complement a yeast PP2C-deficient mutant TM126 (ptc1Δ). Leaf senescence is delayed in the SAG113 knockout mutant compared with that in the wild type, stomatal movement in the senescing leaves of SAG113 knockouts is more sensitive to ABA than that of the wild type, and the rate of water loss in senescing leaves of SAG113 knockouts is significantly reduced. In contrast, inducible over-expression of SAG113 results in a lower sensitivity of stomatal movement to ABA treatment, more rapid water loss, and precocious leaf senescence. No other aspects of growth and development, including seed germination, were observed. These findings suggest that SAG113, a negative regulator of ABA signal transduction, is specifically involved in the control of water loss during leaf senescence.