International Journal of Molecular Sciences

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30 pages, 3354 KiB

Open AccessArticle

Insights into Metabolic Reactions of Semi-Dwarf, Barley Brassinosteroid Mutants to Drought

by Damian Gruszka, Ewa Pociecha, Barbara Jurczyk, Michał Dziurka, Jakub Oliwa, Iwona Sadura and Anna Janeczko

Int. J. Mol. Sci. 2020, 21(14), 5096; https://doi.org/10.3390/ijms21145096 - 19 Jul 2020

Cited by 7 | Viewed by 2639

Abstract

The roles of endogenous brassinosteroids (BRs) in the modulation of reaction to drought and genetic regulation of this process are still obscure. In this study, a multidirectional analysis was performed on semi-dwarf barley (Hordeum vulgare) Near-Isogenic Lines (NILs) and the reference [...] Read more.

The roles of endogenous brassinosteroids (BRs) in the modulation of reaction to drought and genetic regulation of this process are still obscure. In this study, a multidirectional analysis was performed on semi-dwarf barley (Hordeum vulgare) Near-Isogenic Lines (NILs) and the reference cultivar “Bowman” to get insights into various aspects of metabolic reaction to drought. The NILs are defective in BR biosynthesis or signaling and displayed an enhanced tolerance to drought. The BR metabolism perturbations affected the glucose and fructose accumulation under the control and stress conditions. The BR metabolism abnormalities negatively affected the sucrose accumulation as well. However, during drought, the BR-deficient NILs accumulated higher contents of sucrose than the “Bowman” cultivar. Under the control conditions, accumulation of transcripts encoding antioxidant enzymes ascorbate peroxidase (HvAPX) and superoxide dismutase (HvSOD) was BR-dependent. However, during drought, the accumulation of HvAPX transcript was BR-dependent, whereas accumulations of transcripts encoding catalase (HvCAT) and HvSOD were not affected by the BR metabolism perturbations. The obtained results reveal a significant role of BRs in regulation of the HvAPX and HvCAT enzymatic activities under control conditions and the HvAPX and HvSOD activities during physiological reactions to drought. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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14 pages, 1452 KiB

Open AccessArticle

Biological Activities and Molecular Docking of Brassinosteroids 24-Norcholane Type Analogs

by Katy Díaz, Luis Espinoza, Rodrigo Carvajal, Marcos Conde-González, Vladimir Niebla, Andrés F. Olea and Yamilet Coll

Int. J. Mol. Sci. 2020, 21(5), 1832; https://doi.org/10.3390/ijms21051832 - 06 Mar 2020

Cited by 12 | Viewed by 3504

Abstract

The quest and design of new brassinosteroids analogs is a matter of current interest. Herein, the effect of short alkyl side chains and the configuration at C22 on the growth-promoting activity of a series of new brassinosteroid 24-norcholan-type analogs have been evaluated by [...] Read more.

The quest and design of new brassinosteroids analogs is a matter of current interest. Herein, the effect of short alkyl side chains and the configuration at C22 on the growth-promoting activity of a series of new brassinosteroid 24-norcholan-type analogs have been evaluated by the rice leaf inclination test using brassinolide as positive control. The highest activities were found for triol 3 with a C22(S) configuration and monobenzoylated derivatives. A docking study of these compounds into the active site of the Brassinosteroid Insensitive 1(BRI1)–ligand–BRI1-Associated Receptor Kinase 1 (BAK1) complex was performed using AutoDock Vina, and protein–ligand contacts were analyzed using LigPlot⁺. The results suggest that the hydrophobic interactions of ligands with the receptor BRI1^LRR and hydrogen bonding with BAK1 in the complex are important for ligand recognition. For monobenzoylated derivatives, the absence of the hydrophobic end in the alkyl chain seems to be compensated by the benzoyl group. Thus, it would be interesting to determine if this result depends on the nature of the substituent group. Finally, mixtures of S/R triols 3/4 exhibit activities that are comparable or even better than those found for brassinolide. Thus, these compounds are potential candidates for application in agriculture to improve the growth and yield of plants against various types of biotic and abiotic stress. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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18 pages, 3047 KiB

Open AccessArticle

BAK1 Mediates Light Intensity to Phosphorylate and Activate Catalases to Regulate Plant Growth and Development

by Shan Zhang, Cheng Li, Haihua Ren, Tong Zhao, Qi Li, Shufen Wang, Yanfeng Zhang, Fangming Xiao and Xiaofeng Wang

Int. J. Mol. Sci. 2020, 21(4), 1437; https://doi.org/10.3390/ijms21041437 - 20 Feb 2020

Cited by 22 | Viewed by 5240

Abstract

BAK1 (brassinosteroid-insensitive 1 (BRI1) associated receptor kinase 1) plays major roles in multiple signaling pathways as a coreceptor to regulate plant growth and development and stress response. However, the role of BAK1 in high light signaling is still poorly understood. Here we observed [...] Read more.

BAK1 (brassinosteroid-insensitive 1 (BRI1) associated receptor kinase 1) plays major roles in multiple signaling pathways as a coreceptor to regulate plant growth and development and stress response. However, the role of BAK1 in high light signaling is still poorly understood. Here we observed that overexpression of BAK1 in Arabidopsis interferes with the function of high light in promoting plant growth and development, which is independent of the brassinosteroid (BR) signaling pathway. Further investigation shows that high light enhances the phosphorylation of BAK1 and catalase activity, thereby reducing hydrogen peroxide (H₂O₂) accumulation. Catalase3 (CAT3) is identified as a BAK1-interacting protein by affinity purification and LC-MS/MS analysis. Biochemical analysis confirms that BAK1 interacts with and phosphorylates all three catalases (CAT1, CAT2, and CAT3) of the Arabidopsis genome, and the trans-phosphorylation sites of three catalases with BAK1-CD are identified by LC-MS/MS in vitro. Genetic analyses reveal that the BAK1 overexpression plants knocked out all the three CAT genes completely abolishing the effect of BAK1 on suppression of high light-promoted growth. This study first unravels the role of BAK1 in mediating high light-triggered activation of CATs, thereby degrading H₂O₂ and regulating plant growth and development in Arabidopsis. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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17 pages, 4726 KiB

Open AccessArticle

Melatonin Deficiency Confers Tolerance to Multiple Abiotic Stresses in Rice via Decreased Brassinosteroid Levels

by Ok Jin Hwang and Kyoungwhan Back

Int. J. Mol. Sci. 2019, 20(20), 5173; https://doi.org/10.3390/ijms20205173 - 18 Oct 2019

Cited by 31 | Viewed by 3652

Abstract

Melatonin has long been recognized as a positive signaling molecule and potent antioxidant in plants, which alleviates damage caused by adverse conditions such as salt, cold, and heat stress. In this study, we found a paradoxical role for melatonin in abiotic stress responses. [...] Read more.

Melatonin has long been recognized as a positive signaling molecule and potent antioxidant in plants, which alleviates damage caused by adverse conditions such as salt, cold, and heat stress. In this study, we found a paradoxical role for melatonin in abiotic stress responses. Suppression of the serotonin N-acetyltransferase 2 (snat2) gene encoding the penultimate enzyme in melatonin biosynthesis led to simultaneous decreases in both melatonin and brassinosteroid (BR) levels, causing a semi-dwarf with erect leaf phenotype, typical of BR deficiency. Here, we further characterized snat2 rice in terms of grain morphology and abiotic stress tolerance, to determine whether snat2 rice exhibited characteristics similar to those of BR-deficient rice. As expected, the snat2 rice exhibited tolerance to multiple stress conditions including cadmium, salt, cold, and heat, as evidenced by decreased malondialdehyde (MDA) levels and increased chlorophyll levels, in contrast with SNAT2 overexpression lines, which were less tolerant to stress than wild type plants. In addition, the length and width of grain from snat2 plants were reduced relative to the wild type, which is reminiscent of BR deficiency in rice. Other melatonin-deficient mutant rice lines with suppressed BR synthesis (i.e., comt and t5h) also showed tolerance to salt and heat stress, whereas melatonin-deficient rice seedlings without decreased BR levels (i.e., tdc) failed to exhibit increased stress tolerance, suggesting that stress tolerance was increased not by melatonin deficiency alone, but by a melatonin deficiency-mediated decrease in BR. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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Review

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20 pages, 2033 KiB

Open AccessReview

Molecular Mechanisms of Brassinosteroid-Mediated Responses to Changing Environments in Arabidopsis

by Minghui Lv and Jia Li

Int. J. Mol. Sci. 2020, 21(8), 2737; https://doi.org/10.3390/ijms21082737 - 15 Apr 2020

Cited by 33 | Viewed by 5348

Abstract

Plant adaptations to changing environments rely on integrating external stimuli into internal responses. Brassinosteroids (BRs), a group of growth-promoting phytohormones, have been reported to act as signal molecules mediating these processes. BRs are perceived by cell surface receptor complex including receptor BRI1 and [...] Read more.

Plant adaptations to changing environments rely on integrating external stimuli into internal responses. Brassinosteroids (BRs), a group of growth-promoting phytohormones, have been reported to act as signal molecules mediating these processes. BRs are perceived by cell surface receptor complex including receptor BRI1 and coreceptor BAK1, which subsequently triggers a signaling cascade that leads to inhibition of BIN2 and activation of BES1/BZR1 transcription factors. BES1/BZR1 can directly regulate the expression of thousands of downstream responsive genes. Recent studies in the model plant Arabidopsis demonstrated that BR biosynthesis and signal transduction, especially the regulatory components BIN2 and BES1/BZR1, are finely tuned by various environmental cues. Here, we summarize these research updates and give a comprehensive review of how BR biosynthesis and signaling are modulated by changing environments and how these changes regulate plant adaptive growth or stress tolerance. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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15 pages, 2243 KiB

Open AccessReview

The Control of Cell Expansion, Cell Division, and Vascular Development by Brassinosteroids: A Historical Perspective

by Man-Ho Oh, Saxon H. Honey and Frans E. Tax

Int. J. Mol. Sci. 2020, 21(5), 1743; https://doi.org/10.3390/ijms21051743 - 04 Mar 2020

Cited by 46 | Viewed by 6157

Abstract

Steroid hormones are important signaling molecules in plants and animals. The plant steroid hormone brassinosteroids were first isolated and characterized in the 1970s and have been studied since then for their functions in plant growth. Treatment of plants or plant cells with brassinosteroids [...] Read more.

Steroid hormones are important signaling molecules in plants and animals. The plant steroid hormone brassinosteroids were first isolated and characterized in the 1970s and have been studied since then for their functions in plant growth. Treatment of plants or plant cells with brassinosteroids revealed they play important roles during diverse developmental processes, including control of cell expansion, cell division, and vascular differentiation. Molecular genetic studies, primarily in Arabidopsis thaliana, but increasingly in many other plants, have identified many genes involved in brassinosteroid biosynthesis and responses. Here we review the roles of brassinosteroids in cell expansion, cell division, and vascular differentiation, comparing the early physiological studies with more recent results of the analysis of mutants in brassinosteroid biosynthesis and signaling genes. A few representative examples of other molecular pathways that share developmental roles with brassinosteroids are described, including pathways that share functional overlap or response components with the brassinosteroid pathway. We conclude by briefly discussing the origin and conservation of brassinosteroid signaling. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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18 pages, 529 KiB

Open AccessReview

Deviating from the Beaten Track: New Twists in Brassinosteroid Receptor Function

by Sebastian Wolf

Int. J. Mol. Sci. 2020, 21(5), 1561; https://doi.org/10.3390/ijms21051561 - 25 Feb 2020

Cited by 9 | Viewed by 3308

Abstract

A key feature of plants is their plastic development tailored to the environmental conditions. To integrate environmental signals with genetic growth regulatory programs, plants rely on a number of hormonal pathways, which are intimately connected at multiple levels. Brassinosteroids (BRs), a class of [...] Read more.

A key feature of plants is their plastic development tailored to the environmental conditions. To integrate environmental signals with genetic growth regulatory programs, plants rely on a number of hormonal pathways, which are intimately connected at multiple levels. Brassinosteroids (BRs), a class of plant sterol hormones, are perceived by cell surface receptors and trigger responses instrumental in tailoring developmental programs to environmental cues. Arguably, BR signalling is one of the best-characterized plant signalling pathways, and the molecular composition of the core signal transduction cascade seems clear. However, BR research continues to reveal new twists to re-shape our view on this key signalling circuit. Here, exciting novel findings pointing to the plasma membrane as a key site for BR signalling modulation and integration with other pathways are reviewed and new inputs into the BR signalling pathway and emerging “non-canonical” functions of the BR receptor complex are highlighted. Together, this new evidence underscores the complexity of plant signalling integration and serves as a reminder that highly-interconnected signalling pathways frequently comprise non-linear aspects which are difficult to convey in classical conceptual models. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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16 pages, 746 KiB

Open AccessReview

The Role of Brassinosteroids in Controlling Plant Height in Poaceae: A Genetic Perspective

by Giulia Castorina and Gabriella Consonni

Int. J. Mol. Sci. 2020, 21(4), 1191; https://doi.org/10.3390/ijms21041191 - 11 Feb 2020

Cited by 48 | Viewed by 5108

Abstract

The most consistent phenotype of the brassinosteroid (BR)-related mutants is the dwarf habit. This observation has been reported in every species in which BR action has been studied through a mutational approach. On this basis, a significant role has been attributed to BRs [...] Read more.

The most consistent phenotype of the brassinosteroid (BR)-related mutants is the dwarf habit. This observation has been reported in every species in which BR action has been studied through a mutational approach. On this basis, a significant role has been attributed to BRs in promoting plant growth. In this review, we summarize the work conducted in rice, maize, and barley for the genetic dissection of the pathway and the functional analysis of the genes involved. Similarities and differences detected in these species for the BR role in plant development are presented. BR promotes plant cell elongation through a complex signalling cascade that modulates the activities of growth-related genes and through the interaction with gibberellins (GAs), another class of important growth-promoting hormones. Evidence of BR–GA cross-talk in controlling plant height has been collected, and mechanisms of interaction have been studied in detail in Arabidopsis thaliana and in rice (Oryza sativa). The complex picture emerging from the studies has highlighted points of interaction involving both metabolic and signalling pathways. Variations in plant stature influence plant performance in terms of stability and yield. The comprehension of BR’s functional mechanisms will therefore be fundamental for future applications in plant-breeding programs. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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16 pages, 892 KiB

Open AccessReview

Roles of Brassinosteroids in Plant Reproduction

by Zicong Li and Yuehui He

Int. J. Mol. Sci. 2020, 21(3), 872; https://doi.org/10.3390/ijms21030872 - 29 Jan 2020

Cited by 65 | Viewed by 7146

Abstract

Brassinosteroids (BRs) are a group of steroid hormones, essentially important for plant development and growth. BR signaling functions to promote cell expansion and cell division, and plays a role in etiolation and reproduction. As the phytohormone originally identified in the pollen grains of [...] Read more.

Brassinosteroids (BRs) are a group of steroid hormones, essentially important for plant development and growth. BR signaling functions to promote cell expansion and cell division, and plays a role in etiolation and reproduction. As the phytohormone originally identified in the pollen grains of Brassica napus, BR promotes the elongation of stigma. Recent studies have revealed that BR is also critical for floral transition, inflorescence stem architecture formation and other aspects of plant reproductive processes. In this review, we focus on the current understanding of BRs in plant reproduction, the spatial and temporal control of BR signaling, and the downstream molecular mechanisms in both the model plant Arabidopsis and crops. The crosstalk of BR with environmental factors and other hormones in reproduction will also be discussed. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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23 pages, 1824 KiB

Open AccessReview

Exploring the Brassinosteroid Signaling in Monocots Reveals Novel Components of the Pathway and Implications for Plant Breeding

by Damian Gruszka

Int. J. Mol. Sci. 2020, 21(1), 354; https://doi.org/10.3390/ijms21010354 - 05 Jan 2020

Cited by 24 | Viewed by 5126

Abstract

Brassinosteroids (BRs) are a class of steroidal phytohormones which are key regulators of diverse processes during whole life cycle of plants. Studies conducted in the dicot model species Arabidopsis thaliana have allowed identification and characterization of various components of the BR signaling. It [...] Read more.

Brassinosteroids (BRs) are a class of steroidal phytohormones which are key regulators of diverse processes during whole life cycle of plants. Studies conducted in the dicot model species Arabidopsis thaliana have allowed identification and characterization of various components of the BR signaling. It is currently known that the BR signaling is interconnected at various stages with other phytohormonal and stress signaling pathways. It enables a rapid and efficient adaptation of plant metabolism to constantly changing environmental conditions. However, our knowledge about mechanism of the BR signaling in the monocot species is rather limited. Thus, identification of new components of the BR signaling in monocots, including cereals, is an ongoing process and has already led to identification of some monocot-specific components of the BR signaling. It is of great importance as disturbances in the BR signaling influence architecture of mutant plants, and as a consequence, the reaction to environmental conditions. Currently, the modulation of the BR signaling is considered as a target to enhance yield and stress tolerance in cereals, which is of particular importance in the face of global climate change. Full article

(This article belongs to the Special Issue Brassinosteroids and Plant Steroid Hormone Signaling)

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