# DBT JRF 2022 — Question 79

Exam: DBT JRF 2022 · Section: B · Topic: Plant Biology › Male Sterility in Crop Plants · Difficulty: Medium

## Question

Which one of the following genes can be used to generate male sterile crop plants?

## Options

- **A.** Barnase
- **B.** Bar
- **C.** Lectinase
- **D.** Chalcone Synthase

## Answer

Option A

## Explanation

Barnase-barstar system for creating male-sterile plants: Hybrid seed production requires male-sterile female plants (to prevent self-pollination). The barnase/barstar system achieves this: • Barnase: A ribonuclease from Bacillus amyloliquefaciens. • When expressed under the tapetum-specific promoter (TA29) in anthers → barnase degrades RNA in tapetal cells → tapetal cells die → no viable pollen produced → MALE STERILITY. • Barstar: The natural inhibitor of barnase. When expressed in pollen of the 'restorer' line, barstar inhibits barnase → restores fertility. Application in hybrid breeding: 1. Line A (male-sterile): TA29::barnase 2. Line B (restorer): TA29::barstar 3. Cross A×B: hybrid seeds are male-fertile (contain barstar) This system is used in hybrid oilseed rape (canola) production. Answer: Barnase expressed in anthers kills tapetal cells → no pollen formed → male sterility for hybrid seed production.

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