BRASSINOSTEROID BIOSYNTHESIS SIGNALLING AND APPLICATION IN AGRONOMY HORTICULTURE
Dr. Muhammad Shafiq
17 March - 2025
BRASSINOSTEROID BIOSYNTHESIS SIGNALLING AND APPLICATION IN AGRONOMY HORTICULTURE
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Agenda
Introduction to Brassinosteroids
Biosynthesis Pathway
Signalling Mechanisms
Role in Plant Growth
Applications in Agronomy and Horticulture
Benefits for Crop Yield
Challenges in Usage
Future Directions and Conclusion
BRASSINOSTEROID BIOSYNTHESIS SIGNALLING AND APPLICATION IN AGRONOMY HORTICULTURE
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Introduction to Brassinosteroids
Brassinosteroids (BRs) are a class of plant hormones crucial for regulating growth and development. They play significant roles in enhancing stress resistance and overall plant vitality.
Defining Brassinosteroids
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The brassinosteroid (BR) biosynthesis pathway in plants
Step | Description | Key Enzymes |
Sterol Precursors | Conversion of sterols like campesterol into 24-methylenecholesterol or isofucosterol. | Sterol C-24 methyltransferase |
Hydroxylation | Introduction of hydroxyl groups, producing intermediates like cathasterone and teasterone. | CYP90 family enzymes (e.g., DWF4, CPD) |
Oxidation Reactions | Oxidation of hydroxylated intermediates to generate compounds like castasterone. | CYP85 family enzymes |
Formation of Brassinolide | Final conversion of castasterone into brassinolide, the most bioactive brassinosteroid. | CYP85A2 |
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Biosynthesis Pathway
40%
20%
30%
10%
Initial steps in BR biosynthesis
The initial steps of brassinosteroid biosynthesis involve sterol precursors.
Formation of intermediates
Various intermediates are synthesized, leading to bioactive brassinosteroids.
Final enzymatic conversions
Converting intermediates into active brassinosteroids is crucial for their function.
Regulatory processes in biosynthesis
Multiple regulatory mechanisms control brassinosteroid biosynthesis.
Signalling Mechanisms
Brassinosteroids activate specific receptors on plant cells, initiating signaling cascades.
Receptor Activation
Signal transduction involves multiple pathways, enhancing plant response to environmental stimuli.
Transduction Pathways
Signal transduction leads to altered gene expression, affecting growth and development.
Gene Expression
BRASSINOSTEROID BIOSYNTHESIS SIGNALLING AND APPLICATION IN AGRONOMY HORTICULTURE
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Brassinosteroid Signaling Pathway in Plants (Tabular Form)
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Component | Role/Function | Key Details |
Brassinosteroids (BRs) | Plant steroid hormones | Regulate growth, development, and stress response |
BRI1 (BR receptor) | Perception of BRs on cell membrane | Located on plasma membrane; activates signaling upon BR binding |
BAK1 (Co-receptor) | Enhances BRI1 activation | Forms a complex with BRI1 to initiate downstream signaling |
BSK (BR-signaling kinases) | Signal transduction | Phosphorylated by BRI1; transmits the signal downstream |
BIN2 (GSK3-like kinase) | Negative regulator | Suppresses BR signaling in absence of BRs by phosphorylating key transcription factors |
BSU1 (Phosphatase) | Positive regulator | Deactivates BIN2 to promote BR signaling |
BZR1/BES1 (Transcription factors) | Regulate BR-responsive genes | Control genes linked to growth, stress responses, and development |
PP2A (Protein phosphatase 2A) | Dephosphorylates BZR1/BES1 | Activates transcription factors to promote BR responses |
Target Genes | Control growth, stress tolerance, etc. | Include genes for cell elongation, vascular differentiation, and flowering |
Key Functions of Brassinosteroid Signaling in Plants:
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✅ Stem elongation� ✅ Root development� ✅ Flowering and fruit development� ✅ Stress tolerance (e.g., drought, cold)� ✅ Regulation of gene expression for plant growth and immunity
Role in Plant Growth
Brassinosteroids significantly enhance biomass and leaf expansion.
They improve plants' resilience to stressors such as drought, salinity, and extreme temperatures.
Promoting Growth
Stress Resistance
BRASSINOSTEROID BIOSYNTHESIS SIGNALLING AND APPLICATION IN AGRONOMY HORTICULTURE
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Effect of postharvest application of BR on tolerance to disease incidence during storage of horticultural products. EBR: 24-epibrassinolide. DI-31: spirostanic analogs.
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Model of the molecular mechanism of action of BR on (A) fruit development. (B) on ripening of horticultural products in climacteric fruits (left), and climacteric fruits (right),
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APPLICATION | DESCRIPTION |
Disease Resistance | Increase in plant resilience to pathogens. |
Nutrient Use Efficiency | Enhancement of nutrient uptake and utilization. |
Yield Improvement | Significant increase in crop yields. |
Stress Tolerance | Improved tolerance to abiotic stress. |
Quality Enhancement | Better fruit size and quality in crops. |
Agronomic Applications
This table summarizes key agronomic applications of brassinosteroids, highlighting their beneficial roles in agriculture.
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APPLICATION | DESCRIPTION |
Flowering Regulation | Manipulation of flowering time and quality. |
Fruit Development | Enhancement of fruit set and size. |
Post-Harvest Quality | Improvement in shelf life and quality. |
Nutrient Stress Management | Better response to nutrient deficiencies. |
Damping Off Resistance | Reduction of seedling mortality rates. |
Horticultural Applications
This table showcases applications of brassinosteroids in horticulture with notable benefits to cultivation.
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Benefits for Crop Yield
60%
25%
15%
Percentage increase in yields
60% of crops show improved yields when brassinosteroids are utilized.
Effect on soil nutrient health
25% improvement in soil health reported with brassinosteroid application.
Reduction of pest damage
15% reduction in pest-related damage observed in treated crops.
Challenges in Usage
While brassinosteroids have significant benefits, challenges in their application include consistency in efficacy, regulatory hurdles, and potential phytotoxicity. Further research is necessary to address these issues.
Limitations and Challenges
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Future Directions
Future research should focus on understanding the molecular mechanisms and optimizing application methods.
Research Areas
Identifying best practices for brassinosteroid use in commercial farming is essential for maximizing benefits.
Commercial Applications
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Conclusion
In conclusion, brassinosteroids play a vital role in plant growth and agricultural productivity. Their applications in agronomy and horticulture promise enhanced crop performance, although challenges remain.
Final Thoughts
BRASSINOSTEROID BIOSYNTHESIS SIGNALLING AND APPLICATION IN AGRONOMY HORTICULTURE
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