Question

Suppose, you wish to combine the mitochondria from species A with the chloroplast and nucleus of species B. Which of the following techniques is highly suited to achieve the objective?

• A. Isolation and fusion of the protoplasts of both species A and B
• B. Fusion of protoplast of species A with the cytoplast of species B
• C. Fusion of protoplast of species B with the cytoplast of species A
• D. Backcrossing program using species B as recurrent parent

Hint:

In cybridization, the source of the nucleus must always be introduced as an intact, nucleated protoplast, while the source of the desired organelle (like mitochondria) can be supplied as an enucleated cytoplast.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Somatic hybridization and cybridization are cell culture techniques used to fuse protoplasts to generate novel cytoplasmic combinations (cybrids).
A protoplast is a plant cell with its cell wall removed, containing the nucleus and all organelles.
A cytoplast is an enucleated protoplast containing cytoplasm and organelles but lacking a nucleus.

Step 2: Detailed Explanation:
We wish to create a hybrid cell with:
1. Nucleus: Species B
2. Chloroplast: Species B
3. Mitochondria: Species A
Let us analyze the fusion of the protoplast of species B with the cytoplast of species A:
- The protoplast of species B contributes the nucleus of B and the chloroplasts of B.
- The cytoplast of species A contributes the cytoplasm of A, which contains the mitochondria of A, but contains no nucleus.
Upon fusion, the resulting hybrid cell (cybrid) will initially contain the nucleus of species B, alongside a mixture of chloroplasts and mitochondria from both species.
During subsequent cell divisions, organelles undergo random segregation. Because of chloroplast-mitochondrial sorting, cells containing the desired combination (Nucleus B + Chloroplast B + Mitochondria A) can be selected.
This is a standard method to transfer cytoplasmic male sterility (governed by mitochondria) from a donor species (A) into a recipient crop species (B) while preserving the recipient's chloroplasts and nucleus.

Step 3: Final Answer:
Thus, the most suitable technique is the fusion of the protoplast of species B with the cytoplast of species A.