Correct option is B
Explanation-
Lr34 is one of the most well-characterized broad-spectrum resistance (BSR) genes in wheat. It provides partial resistance to multiple pathogens (leaf rust, stripe rust, powdery mildew). It is associated with durable adult plant resistance (APR). Unlike classical resistance genes, Lr34 does not follow gene-for-gene interaction.
Gene Product of Lr34: Encodes an ATP-Binding Cassette (ABC) transporter protein. This transporter is believed to mediate transport of antimicrobial compounds or toxic metabolites across membranes. It plays a role in priming the plant's defense system.
So, the correct answer is option b - ABC transporter.
Incorrect options-
Option a: Serine hydroxymethyl transferase
This is a key metabolic enzyme involved in one-carbon metabolism and folate cycle. This enzyme is involved in basic cellular metabolism, not in plant defense or disease resistance.
It has no known role in pathogen response or transport activity like Lr34.
Option c: Host-specific toxin
These are toxic molecules produced by pathogens, not by the host plant. Host-specific toxins (HSTs) are typically used by pathogens (e.g., fungi like Cochliobolus victoriae) to kill plant cells.
Lr34 is a plant gene, not a pathogen gene, and has no role in toxin production. Also, Lr34 functions without direct pathogen recognition, unlike mechanisms involving HSTs.
Option d: TIR-NB-LRR protein
A classic plant resistance (R) protein, which contains a Toll/Interleukin-1 receptor (TIR) domain , a Nucleotide-Binding (NB) site and Leucine-Rich Repeats (LRR) for pathogen recognition. These are part of effector-triggered immunity (ETI), which follows the gene-for-gene model. Lr34 is not a TIR-NB-LRR protein.
