Vegetative leaves in
are classified as either juvenile leaves or adult leaves based on their specific traits, such as leaf shape and the presence of abaxial trichomes. The timing of the ...juvenile-to-adult phase transition during vegetative development, called the vegetative phase change, is a critical decision for plants, as this transition is associated with crop yield, stress responses, and immune responses. Juvenile leaves are characterized by high levels of miR156/157, and adult leaves are characterized by high levels of miR156/157 targets, SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors. The discovery of this miR156/157-SPL module provided a critical tool for elucidating the complex regulation of the juvenile-to-adult phase transition in plants. In this review, we discuss how the traits of juvenile leaves and adult leaves are determined by the miR156/157-SPL module and how different factors, including embryonic regulators, sugar, meristem regulators, hormones, and epigenetic proteins are involved in controlling the juvenile-to-adult phase transition, focusing on recent insights into vegetative phase change. We also highlight outstanding questions in the field that need further investigation. Understanding how vegetative phase change is regulated would provide a basis for manipulating agricultural traits under various conditions.
Leaves are the major organ for photosynthesis in most land plants, and leaf structure is optimized for the maximum capture of sunlight and gas exchange. Three polarity axes, the adaxial-abaxial axis, ...the proximal-distal axis, and the medial-lateral axis are established during leaf development to give rise to a flattened lamina with a large area for photosynthesis and blades that are extended on petioles for maximum sunlight. Adaxial cells are elongated, tightly packed cells with many chloroplasts, and their fate is specified by HD-ZIP III and related factors. Abaxial cells are rounder and loosely packed cells and their fate is established and maintained by YABBY family and KANADI family proteins. The activities of adaxial and abaxial regulators are coordinated by ASYMMETRIC LEAVES2 and auxin. Establishment of the proximodistal axis involves the BTB/POZ domain proteins BLADE-ON-PETIOLE1 and 2, whereas homeobox genes PRESSED FLOWER and WUSCHEL-RELATED HOMEOBOX1 mediate leaf development along the mediolateral axis. This review summarizes recent advances in leaf polarity establishment with a focus on the regulatory networks involved.
•We investigate co-movement between oil and stock market in time–frequency space.•Crude oil is the main driver of co-movement in the mid- and long-term scales.•Crude oil rarely affects the ...co-movement in oil-importing countries’ stock markets.•GCC stock markets lead over oil-importing countries’ stock markets in the long term.
In this paper, we employ partial- and multiple-wavelet coherence analyses to examine co-movement between international stock markets by considering the influence of crude oil in a time domain perspective. Overall, we find that crude oil is a major factor driving co-movement between international stock markets in the median and long term. However, when considering the oil-importing and oil-exporting countries differently, we still find that crude oil is a driver for interdependence between oil-importing and oil-exporting countries. In contrast, the crude oil has relative lower impact on the co-movement in oil-importing or in oil-exporting countries, which indicates its co-movement is caused by other factors. In addition, Gulf Cooperation Council stock market may lead the stock markets of oil-importing countries in the long term. Our empirical results provide meaningful information for investors and policymakers.
Correct developmental timing is essential for plant fitness and reproductive success. Two important transitions in shoot development-the juvenile-to-adult vegetative transition and the ...vegetative-to-reproductive transition-are mediated by a group of genes targeted by miR156, SQUAMOSA PROMOTER BINDING PROTEIN (SBP) genes. To determine the developmental functions of these genes in Arabidopsis thaliana, we characterized their expression patterns, and their gain-of-function and loss-of-function phenotypes. Our results reveal that SBP-LIKE (SPL) genes in Arabidopsis can be divided into three functionally distinct groups: 1) SPL2, SPL9, SPL10, SPL11, SPL13 and SPL15 contribute to both the juvenile-to-adult vegetative transition and the vegetative-to-reproductive transition, with SPL9, SP13 and SPL15 being more important for these processes than SPL2, SPL10 and SPL11; 2) SPL3, SPL4 and SPL5 do not play a major role in vegetative phase change or floral induction, but promote the floral meristem identity transition; 3) SPL6 does not have a major function in shoot morphogenesis, but may be important for certain physiological processes. We also found that miR156-regulated SPL genes repress adventitious root development, providing an explanation for the observation that the capacity for adventitious root production declines as the shoot ages. miR156 is expressed at very high levels in young seedlings, and declines in abundance as the shoot develops. It completely blocks the expression of its SPL targets in the first two leaves of the rosette, and represses these genes to different degrees at later stages of development, primarily by promoting their translational repression. These results provide a framework for future studies of this multifunctional family of transcription factors, and offer new insights into the role of miR156 in Arabidopsis development.
Vegetative phase change in flowering plants is regulated by a decrease in the level of miR156. The molecular mechanism of this temporally regulated decrease in miR156 expression is still unknown. ...Most of the miR156 in Arabidopsis thaliana shoots is produced by MIR156A and MIR156C. We found that the downregulation of these genes during vegetative phase change is associated with an increase in their level of histone H3 lysine 27 trimethylation (H3K27me3) and requires this chromatin modification. The increase in H3K27me3 at MIR156A/MIR156C is associated with an increase in the binding of PRC2 to these genes and is mediated redundantly by the E(z) homologs SWINGER and CURLY LEAF. The CHD3 chromatin remodeler PICKLE (PKL) promotes the addition of H3K27me3 to MIR156A/MIR156C but is not responsible for the temporal increase in this chromatin mark. PKL is bound to the promoters of MIR156A/MIR156C, where it promotes low levels of H3K27ac early in shoot development and stabilizes the nucleosome at the +1 position. These results suggest a molecular mechanism for the initiation and maintenance of vegetative phase change in plants.
Vegetative phase change is regulated by a decrease in the abundance of the miRNAs, miR156 and miR157, and the resulting increase in the expression of their targets, SQUAMOSA PROMOTER BINDING ...PROTEIN-LIKE (SPL) transcription factors. To determine how miR156/miR157 specify the quantitative and qualitative changes in leaf morphology that occur during vegetative phase change, we measured their abundance in successive leaves and characterized the phenotype of mutations in different MIR156 and MIR157 genes. miR156/miR157 decline rapidly between leaf 1&2 and leaf 3 and decrease more slowly after this point. The amount of miR156/miR157 in leaves 1&2 greatly exceeds the threshold required to specify their identity. Subsequent leaves have relatively low levels of miR156/miR157 and are sensitive to small changes in their abundance. In these later-formed leaves, the amount of miR156/miR157 is close to the threshold required to specify juvenile vs. adult identity; a relatively small decrease in the abundance of miR156/157 in these leaves produces a disproportionately large increase in SPL proteins and a significant change in leaf morphology. miR157 is more abundant than miR156 but has a smaller effect on shoot morphology and SPL gene expression than miR156. This may be attributable to the inefficiency with which miR157 is loaded onto AGO1, as well as to the presence of an extra nucleotide at the 5' end of miR157 that is mis-paired in the miR157:SPL13 duplex. miR156 represses different targets by different mechanisms: it regulates SPL9 by a combination of transcript cleavage and translational repression and regulates SPL13 primarily by translational repression. Our results offer a molecular explanation for the changes in leaf morphology that occur during shoot development in Arabidopsis and provide new insights into the mechanism by which miR156 and miR157 regulate gene expression.
The interleukin (IL)-6/IL-12 family cytokines have pleiotropic functions and play critical roles in multiple immune responses. This cytokine family has very unique characteristics in that they ...comprise two distinct subunits forming a heterodimer and each cytokine and receptor subunit shares with each other. The members of this cytokine family are increasing; currently, there are more than six cytokines, including the tentatively named cytokines IL-Y (p28/p40), IL-12 (p35/p40), IL-23 (p19/p40), IL-27 p28/Epstein-Barr virus-induced protein 3 (EBI3), IL-35 (p35/EBI3), and IL-39 (p19/EBI3). This family of cytokines covers a very broad range of immune responses, including pro-inflammatory responses, such as helper T (Th)1, Th2, and Th17, to anti-inflammatory responses, such as regulatory T (Treg) cells and IL-10-producing Treg cells. IL-12 is the first member of this family, and IL-12, IL-23, and IL-27 are mainly produced by activated antigen-presenting cells, such as dendritic cells and macrophages. IL-12 plays a critical role in the promotion of Th1 immune responses by inducing interferon-γ production to combat pathogens and malignant tumors. IL-23 induces IL-17 production and is necessary to maintain pathogenic Th17 cells that cause inflammatory and autoimmune diseases. IL-27 was initially reported to play a critical role in promotion of Th1 differentiation; however, subsequent studies revealed that IL-27 has broader stimulatory and inhibitory roles by inducing IL-10-producing Treg cells. IL-35 is produced by forkhead box P3
Treg cells and activated B cells and has immunosuppressive functions to maintain immune tolerance. The most recently identified cytokine, IL-39, is produced by activated B cells and has pro-inflammatory functions. The cytokine tentatively named IL-Y seems to have anti-inflammatory functions by inhibiting Th1 and Th17 differentiation. In addition, individual cytokine subunits were also shown to have self-standing activities. Thus, promiscuity within the IL-6/IL-12 family cytokines complicates structural and functional clarification and assignment of individual cytokines. A better understanding of the recent advances and expanding diversity in molecular structures and functions of the IL-6/IL-12 family cytokines could allow the creation of novel therapeutic strategies by using them as tools and targeted molecules.
Correct timing of developmental phase transitions is critical for the survival and fitness of plants. Developmental phase transitions in plants are partially promoted by controlling relevant genes ...into active or repressive status. Polycomb Repressive Complex1 (PRC1) and PRC2, originally identified in Drosophila, are essential in initiating and/or maintaining genes in repressive status to mediate developmental phase transitions. Our review summarizes mechanisms in which the embryo-to-seedling transition, the juvenile-to-adult transition, and vegetative-to-reproductive transition in plants are mediated by PRC1 and PRC2, and suggests that PRC1 could act either before or after PRC2, or that they could function independently of each other. Details of the exact components of PRC1 and PRC2 in each developmental phase transitions and how they are recruited or removed will need to be addressed in the future.
Nutrients shape the growth, maturation, and aging of plants and animals. In plants, the juvenile to adult transition (vegetative phase change) is initiated by a decrease in miR156. In Arabidopsis, we ...found that exogenous sugar decreased the abundance of miR156, whereas reduced photosynthesis increased the level of this miRNA. This effect was correlated with a change in the timing of vegetative phase change, and was primarily attributable to a change in the expression of two genes, MIR156A and MIR156C, which were found to play dominant roles in this transition. The glucose-induced repression of miR156 was dependent on the signaling activity of HEXOKINASE1. We also show that the defoliation-induced increase in miR156 levels can be suppressed by exogenous glucose. These results provide a molecular link between nutrient availability and developmental timing in plants, and suggest that sugar is a component of the leaf signal that mediates vegetative phase change. DOI:http://dx.doi.org/10.7554/eLife.00260.001.
Hydrogel-tethered polysulfone (PSF) membranes have been synthesized by grafting propargyl-poly(ethylene glycol) (pro-PEG) onto azide-functionalized PSF membrane surfaces via the copper (Ι) catalyzed ...azide-alkyne cycloaddition (CuAAC) reaction, and then used for oil/water emulsion purification. Three pro-PEGs (120, 750 and 1300g/moL) and two PSF-azi membranes with different degrees of azide functionality were used to obtain a series of PSF-g-PEG membranes. The membranes were characterized in detail by FTIR, XPS, FESEM and the contact angle method. The click reaction was demonstrated to be effective, and PEG was densely and highly uniformly grafted on the membrane surfaces including the pore walls. A higher hydrodynamic thickness of the PEG layer leads to a lower contact angle. The grafting density has more impact on membrane properties than the PEG molecular weight. The membrane grafted with low-molecular weight PEG at high grafting density shows a better combination of antifouling performance and permeance. The best performance was 120Lm−2h−1 emulsion flux with complete oil rejection and over 95% flux recovery in cycled fouling-rinsing tests. It is suggested that high grafting density should be pursued with strict control on the chain length to obtain good emulsion filtration membranes.
•PEG tethered PSF membrane was fabricated for oil/water emulsion purification.•PEG was grafted densely and uniformly on membrane surface by click chemistry.•Higher hydrodynamic thickness leads to lower WCA values.•The grafting density has more impact on membrane properties than the PEG MW.•High grafting density and low grafting MW required achieving good performance.
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