Background: Why Phosphorus Matters
- Phosphorus (P) is critical for:
- Root development
- Flowering & grain formation
- Photosynthesis and energy transfer (ATP)
- India’s soil challenge:
- Widespread phosphorus deficiency, esp. in acidic or alkaline soils.
- India imports nearly all of its phosphate fertilizer needs.
- Efficiency crisis: Plants absorb only 15–20% of applied phosphate; the rest is lost to runoff or leaching.
Relevance : GS 3(Agriculture , Science and Technology)
The Breakthrough: CRISPR-Cas9 for Root-to-Shoot Phosphate Transport
- Led by: Dr. Jitender Giri, NIPGR (Delhi)
- Focused on japonica rice (cv. Nipponbare) in controlled greenhouse settings.
- Target gene: OsPHO1;2 – responsible for phosphate transport from root to shoot.
Genetic Engineering: From Silencing to Precision Editing
Failed Attempt: Knocking out the Repressor (OsWRKY6)
- Researchers silenced OsWRKY6 (a negative regulator).
- Result: Higher phosphate transport → but poor plant growth.
- Cause: OsWRKY6 also regulates other vital processes.
Successful Strategy: Editing Just the Repressor’s Binding Site
- Used CRISPR–Cas9 to remove 30 bp binding site on OsPHO1;2 promoter.
- Outcome:
- Repressor remains intact (continues other functions).
- OsPHO1;2 expression upregulated → improved phosphate transport.
- Phosphate absorbed faster before it binds with Al, Fe, Ca, Mg in soil.
Results: Yields, Efficiency, and Seed Quality
- With recommended fertilizer: yield increased by 20%
- With only 10% fertilizer dose: yield increased by 40% over control!
- Mechanism:
- Roots behave like sinks, absorbing more phosphate.
- Enhanced shoot phosphate → more panicles → more seeds
- Seed quality intact: No negative change in starch, dimensions, phosphate content.
Technical Safeguards: Precision & Bioethics
Off-target effects:
- Verified using in silico tools + top 10 predicted sites: no off-target changes.
Foreign DNA removal:
- Cas9 & vector DNA removed via Mendelian segregation in 2nd generation.
- Non-transgenic, precisely edited lines selected for seed generation.
Testing:
- Southern blot and junction fragment analysis used to confirm:
- No partial insertions
- Clean genome edits
Implications for Indian Agriculture
- Indica rice adaptation is pending but underway — more time-intensive.
- When adapted, it could:
- Reduce India’s import dependence on phosphate.
- Promote low-input sustainable farming in phosphorus-poor regions.
- Benefit small and marginal farmers facing fertilizer affordability issues.
- Ecological value:
- Reduced runoff = lower eutrophication
- Efficient use = resource conservation
Expert Validation
- Dr. P.V. Shivaprasad (NCBS, Bengaluru): “If replicated in indica rice, this could revolutionise farming in India’s phosphorus-deficient soils.”
- Dr. Giri (NIPGR): “This is like a minimally invasive genome surgery — precise, targeted, and transformative.”
