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    WRKY9 transcription factor regulates cytochrome P450 genes CYP94B3 and CYP86B1, leading to increased root suberin and salt tolerance in Arabidopsis
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    Abstract:
    Salinity affects crop productivity worldwide and mangroves growing under high salinity exhibit adaptations such as enhanced root apoplastic barrier to survive under such conditions. We have identified two cytochrome P450 family genes, AoCYP94B3 and AoCYP86B1 from the mangrove tree Avicennia officinalis and characterized them using atcyp94b3 and atcyp86b1, which are mutants of their putative Arabidopsis orthologs and the corresponding complemented lines with A. officinalis genes. CYP94B3 and CYP86B1 transcripts were induced upon salt treatment in the roots of both A. officinalis and Arabidopsis. Both AoCYP94B3 and AoCYP86B1 were localized to the endoplasmic reticulum. Heterologous expression of 35S::AoCYP94B3 and 35S::AoCYP86B1 in their respective Arabidopsis mutants (atcyp94b3 and atcyp86b1) increased the salt tolerance of the transgenic seedlings by reducing the amount of Na+ accumulation in the shoots. Moreover, the reduced root suberin phenotype of atcyp94b3 was rescued in the 35S::AoCYP94B3;atcyp94b3 transgenic Arabidopsis seedlings. Gas-chromatography and mass spectrometry analyses showed that the amount of suberin monomers (C-16 ω-hydroxy acids, C-16 α, ω-dicarboxylic acids and C-20 eicosanol) were increased in the roots of 35S::AoCYP94B3;atcyp94b3 Arabidopsis seedlings. Using chromatin immunoprecipitation and electrophoretic mobility shift assays, we identified AtWRKY9 as the upstream regulator of AtCYP94B3 and AtCYP86B1 in Arabidopsis. In addition, atwrky9 showed suppressed expression of AtCYP94B3 and AtCYP86B1 transcripts, and reduced suberin in the roots. These results show that AtWRKY9 controls suberin deposition by regulating AtCYP94B3 and AtCYP86B1, leading to salt tolerance. Our data can be used for generating salt-tolerant crop plants in the future.
    Keywords:
    Suberin
    Salinity affects crop productivity worldwide and mangroves growing under high salinity exhibit adaptations such as enhanced root apoplastic barrier to survive under such conditions. We have identified two cytochrome P450 family genes, AoCYP94B3 and AoCYP86B1 from the mangrove tree Avicennia officinalis and characterized them using atcyp94b3 and atcyp86b1, which are mutants of their putative Arabidopsis orthologs and the corresponding complemented lines with A. officinalis genes. CYP94B3 and CYP86B1 transcripts were induced upon salt treatment in the roots of both A. officinalis and Arabidopsis. Both AoCYP94B3 and AoCYP86B1 were localized to the endoplasmic reticulum. Heterologous expression of 35S::AoCYP94B3 and 35S::AoCYP86B1 in their respective Arabidopsis mutants (atcyp94b3 and atcyp86b1) increased the salt tolerance of the transgenic seedlings by reducing the amount of Na+ accumulation in the shoots. Moreover, the reduced root suberin phenotype of atcyp94b3 was rescued in the 35S::AoCYP94B3;atcyp94b3 transgenic Arabidopsis seedlings. Gas-chromatography and mass spectrometry analyses showed that the amount of suberin monomers (C-16 ω-hydroxy acids, C-16 α, ω-dicarboxylic acids and C-20 eicosanol) were increased in the roots of 35S::AoCYP94B3;atcyp94b3 Arabidopsis seedlings. Using chromatin immunoprecipitation and electrophoretic mobility shift assays, we identified AtWRKY9 as the upstream regulator of AtCYP94B3 and AtCYP86B1 in Arabidopsis. In addition, atwrky9 showed suppressed expression of AtCYP94B3 and AtCYP86B1 transcripts, and reduced suberin in the roots. These results show that AtWRKY9 controls suberin deposition by regulating AtCYP94B3 and AtCYP86B1, leading to salt tolerance. Our data can be used for generating salt-tolerant crop plants in the future.
    Suberin
    Citations (38)
    ABSTRACT Angiosperm roots, except in Arabidopsis, have both endodermis and exodermis, which regulate radial water and solute movement through lignin and suberin deposition. While endodermal suberin in Arabidopsis acts as a barrier to water and solute uptake and backflow, its implications in other angiosperms with both layers and the role of exodermal suberin remain unclear. We examined potato roots ( Solanum tuberosum ) and found that exodermis lacks the typical Casparian strip but forms an outer lignin cap, and quickly suberizes near the root tip. In contrast, a few endodermal cells, with Casparian strip, start suberizing much later. The continuous early exodermal suberization covering the root underlines its potential role in mineral nutrient radial movement. To demonstrate it, we used plants downregulating the suberin biosynthetic gene CYP86A33 , which had the root suberin reduced in a 61%. Phenotypic analyses of the suberin-deficient mutant showed altered mineral nutrient concentration, slightly reduced water content and compromised growth. Micro-PIXE analyses identified the distribution of elements within the roots and highlighted anatomical compartments defined by apoplastic barriers. These findings advance our understanding of nutrient radial transport, demonstrate exodermal suberin as a bidirectional and selective barrier to element movement, and underscore its importance in nutrient homeostasis and plant growth.
    Suberin
    Endodermis
    Citations (1)
    Plant cell walls are dramatically affected by suberin deposition, becoming an impermeable barrier to water and pathogens. Suberin is a complex layered heteropolymer that comprises both a poly(aliphatic) and a poly(aromatic) lignin-like domain. Current structural models for suberin attribute the crosslinking of aliphatic and aromatic domains within the typical lamellar ultrastructure of the polymer to esterified ferulate. BAHD feruloyl transferases involved in suberin biosynthesis have been recently characterized in Arabidopsis and potato (Solanum tuberosum). In defective mutants, suberin, even lacks most of the esterified ferulate, but maintains the typical lamellar ultrastructure. However, suberized tissues display increased water permeability, in spite of exhibiting a similar lipid load to wild type. Therefore, the role of ferulate in suberin needs to be reconsidered. Moreover, silencing the feruloyl transferase in potato turns the typical smooth skin of cv. Desirée into a rough scabbed skin distinctive of Russet varieties and impairs the normal skin maturation that confers resistance to skinning. Concomitantly to these changes, the skin of silenced potatoes shows an altered profile of soluble phenolics with the emergence of conjugated polyamines.
    Suberin
    Endodermis
    Solanum tuberosum
    Citations (28)
    A protocol is outlined for histochemical detection of intracellular suberin linings on the inner surface of the cell walls in impervious tissues of wounded and infected bark, and in bark forming rhytidome. Thin intracellular suberin linings (circa 0.5 µ m) were detected in all 15 woody angiosperms examined. Intracellular suberisation was strongly associated with individual cells or cell layers (boundary zone) that displayed imperviousness with fluid diffusion tests. Tests inc1ude use of phloroglucinol + HCl and Sudan black B to selectively quench autofluorescence of lignin and suberin, respectively. Blue-violet excitation is used to enhance the Sudan IV test for suberin, cutin, and waxes.
    Suberin
    Cutin
    Endodermis
    Sudan Black B
    Frost (temperature)
    Citations (70)
    Abstract In plants, 14-3-3 proteins are key regulators of primary metabolism and membrane transport. Although the current dogma states that 14-3-3 isoforms are not very specific with regard to target proteins, recent data suggest that the specificity may be high. Therefore, identification and characterization of all 14-3-3 (GF14) isoforms in the model plant Arabidopsis are important. Using the information now available from The Arabidopsis Information Resource, we found three new GF14 genes. The potential expression of these three genes, and of two additional novel GF14 genes (Rosenquist et al., 2000), in leaves, roots, and flowers was examined using reverse transcriptase-polymerase chain reaction and cDNA library polymerase chain reaction screening. Under normal growth conditions, two of these genes were found to be transcribed. These genes were namedgrf11and grf12, and the corresponding new 14-3-3 isoforms were named GF14omicron and GF14iota, respectively. The gene coding for GF14omicron was expressed in leaves, roots, and flowers, whereas the gene coding for GF14iota was only expressed in flowers. Gene structures and relationships between all members of the GF14 gene family were deduced from data available through The Arabidopsis Information Resource. The data clearly support the theory that two 14-3-3 genes were present when eudicotyledons diverged from monocotyledons. In total, there are 15 14-3-3 genes (grfs 1–15) in Arabidopsis, of which 12 (grfs 1–12) now have been shown to be expressed.
    Citations (181)
    The permeability of roots to water and nutrients is controlled through a variety of mechanisms and one of the most conspicuous is the presence of the Casparian strips and suberin lamellae. Roots actively regulate the creation of these structures developmentally, along the length of the root, and in response to the environment, including drought. In the current study, we characterized the suberin composition along the length of grapevine fine roots during development and in response to water deficit, and in the same root systems we quantified changes in expression of suberin biosynthesis- and deposition-related gene families (via RNAseq) allowing the identification of drought-responsive suberin-related genes. Grapevine suberin composition did not differ between primary and lateral roots, and was similar to that of other species. Under water deficit there was a global upregulation of suberin biosynthesis which resulted in an increase of suberin specific monomers, but without changes in their relative abundances, and this upregulation took place across all the developmental stages of fine roots. These changes corresponded to the upregulation of numerous suberin biosynthesis- and export-related genes which included orthologs of the previously characterized AtMYB41 transcriptional factor. Functional validation of two grapevine MYB41 orthologs, VriMYB41 and VriMYB41-like, confirmed their ability to globally upregulate suberin biosynthesis, export, and deposition. This study provides a detailed characterization of the developmental and water deficit induced suberization of grapevine fine roots and identifies important orthologs responsible for suberin biosynthesis, export, and its regulation in grape.
    Suberin
    Endodermis
    Citations (25)
    ABSTRACT The permeability of roots to water and nutrients is controlled through a variety of mechanisms and one of the most conspicuous is the presence of structures such as the Casparian strips and suberin lamellae. Roots actively regulate the creation of these structures developmentally, along the length of the root, and in response to the environment, including abiotic stresses such as drought. In the current study, we characterized the suberin composition along the length of grapevine fine roots during development and in response to water deficit. In parallel samples we quantified changes in expression of suberin biosynthesis- and deposition-related gene families (via RNAseq) allowing the identification of drought-responsive suberin-related genes. Grapevine suberin composition did not differ between primary and lateral roots, and was similar to that of other species. Under water deficit there was a global upregulation of suberin biosynthesis which resulted in an increase of suberin specific monomers, but without changes in their relative abundances, and this upregulation took place across all the developmental stages of fine roots. These changes corresponded to the upregulation of numerous suberin biosynthesis- and deposition-related genes which included orthologs of the previously characterized AtMYB41 transcriptional factor. Functional validation of two grapevine MYB41 orthologs, VviMYB41 and VviMYB41-like, confirmed their ability to globally upregulate suberin biosynthesis and deposition. This study provides a detailed characterization of the developmental and water deficit induced suberization of grapevine fine roots and identifies important orthologs responsible for suberin biosynthesis, deposition, and its regulation in grape. One sentence summary Our study details the biochemical changes and molecular regulation of how grapevines decrease their root permeability during drought.
    Suberin
    Endodermis
    Citations (0)
    Acyl lipids in Arabidopsis and all other plants have a myriad of diverse functions. These include providing the core diffusion barrier of the membranes that separates cells and subcellular organelles. This function alone involves more than 10 membrane lipid classes, including the phospholipids, galactolipids, and sphingolipids, and within each class the variations in acyl chain composition expand the number of structures to several hundred possible molecular species. Acyl lipids in the form of triacylglycerol account for 35% of the weight of Arabidopsis seeds and represent their major form of carbon and energy storage. A layer of cutin and cuticular waxes that restricts the loss of water and provides protection from invasions by pathogens and other stresses covers the entire aerial surface of Arabidopsis. Similar functions are provided by suberin and its associated waxes that are localized in roots, seed coats, and abscission zones and are produced in response to wounding. This chapter focuses on the metabolic pathways that are associated with the biosynthesis and degradation of the acyl lipids mentioned above. These pathways, enzymes, and genes are also presented in detail in an associated website (ARALIP: http://aralip.plantbiology.msu.edu/). Protocols and methods used for analysis of Arabidopsis lipids are provided. Finally, a detailed summary of the composition of Arabidopsis lipids is provided in three figures and 15 tables.
    Cutin
    Suberin
    Galactolipids
    Sphingolipid
    Organelle
    Membrane Lipids
    Citations (292)
    Abstract Seven peach clones were assessed for wound response using suberin deposition, lignification, and lignification + suberization as criteria. Suberin and lignin were measured fluorometrically using a new technique that permits unimpeded observation of suberin autofluorescence. Suberin deposition was first observed in cells of the impervious tissue which forms prior to phellogen generation at the wound. Suberin deposition measured as early as 7 days postwounding was negatively correlated with peach canker incidence.
    Suberin
    Deposition
    Citations (13)
    Acyl lipids in Arabidopsis and all other plants have a myriad of diverse functions. These include providing the core diffusion barrier of the membranes that separates cells and subcellular organelles. This function alone involves more than 10 membrane lipid classes, including the phospholipids, galactolipids, and sphingolipids, and within each class the variations in acyl chain composition expand the number of structures to several hundred possible molecular species. Acyl lipids in the form of triacylglycerol account for 35% of the weight of Arabidopsis seeds and represent their major form of carbon and energy storage. A layer of cutin and cuticular waxes that restricts the loss of water and provides protection from invasions by pathogens and other stresses covers the entire aerial surface of Arabidopsis. Similar functions are provided by suberin and its associated waxes that are localized in roots, seed coats, and abscission zones and are produced in response to wounding. This chapter focuses on the metabolic pathways that are associated with the biosynthesis and degradation of the acyl lipids mentioned above. These pathways, enzymes, and genes are also presented in detail in an associated website (ARALIP: http://aralip.plantbiology.msu.edu/). Protocols and methods used for analysis of Arabidopsis lipids are provided. Finally, a detailed summary of the composition of Arabidopsis lipids is provided in three figures and 15 tables.
    Cutin
    Suberin
    Galactolipids
    Sphingolipid
    Organelle
    Membrane Lipids
    Citations (1,321)