Following statements are made about nitrate transporters in plant cells:

A. Nitrate uptake displays two saturable phases, with K_m in the micromolar (μM) range for the high-affinity system and in the millimolar (mM) range for the low-affinity system.
B. The Arabidopsis AtNRT1·1 is a dual-affinity nitrate transporter.
C. AtNRT1·2 participates in high-affinity uptake.
D. AtNRT2·1 and AtNRT2·2 are involved in low-affinity uptake.

Select the option that has the combination of all correct statements:

Correct option is C

Explanation-

Statement A - Nitrate uptake displays two saturable phases, with Kₘ in the micromolar (µM) range for the high-affinity system and in the millimolar (mM) range for the low-affinity system - CORRECT
Plants have two nitrate uptake systems:
   1.  High-affinity transport system (HATS): active at low external nitrate concentrations (Kₘ ≈ µM)
   2.  Low-affinity transport system (LATS): operates at high external concentrations (Kₘ ≈ mM)
Statement B -  The Arabidopsis AtNRT1.1 is a dual-affinity nitrate transporter  - CORRECT
AtNRT1.1 (also known as CHL1 or NPF6.3) can switch between high- and low-affinity modes depending on its phosphorylation state.
Statement C -  AtNRT1.2 participates in high-affinity uptake  - INCORRECT
AtNRT1.2 is not involved in high-affinity uptake. It belongs to the low-affinity nitrate transporter group.
Statement D -  AtNRT2.1 and AtNRT2.2 are involved in low-affinity uptake  - INCORRECT
AtNRT2.1 and AtNRT2.2 are high-affinity nitrate transporters, not low-affinity.

Final Answer:
Correct statements: A and B only (Option c)

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