Question

To increase the amount of mugineic acid, rice plants were transformed (using Agrobacterium) with a fragment of barley genomic DNA containing two naat genes; naat-A and naat-B, encoding the subunits of the enzyme

• A. S-adenosylmethionine synthetase
• B. Nicotinamine aminotransferase
• C. Nicotinamine synthase
• D. Deoxymugineic acid synthase

Hint:

In molecular biology questions, gene names are often acronyms or abbreviations of the enzyme or protein they encode. Pay close attention to these abbreviations, as they provide a direct clue to the answer (e.g., {naat} for Nicotinamine Aminotransferase).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The question describes a genetic engineering experiment to enhance the production of mugineic acid in rice. It specifically mentions the introduction of two genes abbreviated as {naat-A} and {naat-B} and asks for the name of the enzyme they encode.
Step 2: Key Formula or Approach:
The key to solving this question lies in understanding the nomenclature used in molecular biology and biochemistry. The gene name often directly corresponds to the enzyme it encodes. Here, the gene is named {naat}. We need to identify the enzyme name that corresponds to this abbreviation.
Step 3: Detailed Explanation:
Let's break down the biosynthesis pathway for mugineic acids (a type of phytosiderophore): \[ \text{Methionine} \rightarrow \text{S-adenosylmethionine (SAM)} \xrightarrow{\text{NAS}} \text{Nicotianamine (NA)} \xrightarrow{\text{NAAT}} \text{3''-deamino-3''-oxonicotianamine} \xrightarrow{\text{DMAS}} \text{Deoxymugineic acid (DMA)} \rightarrow \text{Mugineic acid} \] The enzymes involved are:

NAS: Nicotianamine Synthase
NAAT: Nicotianamine Aminotransferase
DMAS: Deoxymugineic Acid Synthase
The question explicitly states that the introduced genes are {naat-A} and {naat-B}. The abbreviation {naat} directly stands for Nicotianamine Aminotransferase. Therefore, these genes encode the subunits of the enzyme Nicotinamine aminotransferase.
Step 4: Final Answer:
The genes {naat-A} and {naat-B} encode the enzyme Nicotinamine aminotransferase.