Genetic screens for mutants affecting development of leaf trichomes have led to the discovery of genes regulating trichome patterning-especially tirchome density and spacing, as depicted in the figure below.

(from Taiz et al, Plant Physiology and Development, 6^th edition)

The following statements are made in this regard:

A. GLABRAI (GLI) mutant plant will show fewer or no trichomes.

B.Cells that form trichomes strongly express the GLABRA2(GL2) and TRYPTICON (TRY) genes.

C. TRY protein acts as positive regulator of trichome cell differentiation in the surrounding cells.

D. Addition of exogenous JA will reduce the number of leaf trichomes.

Which one of the following options represents the combination of all correct statements?

Correct option is A

Leaf trichomes (hair-like structures) in plants are regulated by key genes like GLABRA1 (GL1), GLABRA2 (GL2), TRY, and TTG1. These genes control trichome formation and spacing through gene expression and protein interactions.

Analysis of Statements:

1. Statement A: Correct 

   • GLABRA1 (GL1) is essential for trichome formation.
   • Mutants lacking GL1 exhibit fewer or no trichomes, as GL1 interacts with TTG1 and GL3 to initiate trichome cell differentiation.
   • Since GL1 mutants reduce trichome formation, this statement is correct.

2. Statement B: Correct 

   • Cells that form trichomes highly express GLABRA2 (GL2) and TRYPTICON (TRY).
   • GL2 is required for trichome differentiation, while TRY regulates spacing and trichome patterning.
   • Since trichome cells express GL2 and TRY, this statement is correct.

3. Statement C: Incorrect 

   • TRY does not act as a positive regulator of trichome differentiation.
   • Instead, TRY is a negative regulator that inhibits trichome formation in neighboring cells, ensuring proper spacing.
   • Since TRY actually prevents excessive trichome formation, this statement is incorrect.

4. Statement D: Incorrect 

   • Jasmonic acid (JA) promotes trichome formation, rather than reducing it.
   • Studies show that exogenous JA increases trichome density, helping plants resist herbivory.
   • Since JA enhances trichome development, this statement is incorrect.