- Many factors related to the role of abscisic acid (ABA) in contributing to drought, cold and salt resistance in plants are listed below:
A. The transcription factors DREB 1 and DREB2 bind to the cis-acting elements of the promoter of ABA responsive genes in an ABA dependent manner.
B. ABA induces many genes such as LEA and RD29.
C. ABA-responsive genes contain six nucleotide ABRE elements in the promoter.
D. Nine-nucleotide dehydration- responsive elements (DRE) are present in ABA responsive genes.
Which one of the following combinations of the above statements is correct with respect to ABA?
(1) A, B and C (2) A, C and D
(3) B, C and D (4) A only
Correct answer: (3) B, C and D
Explanation:
-
(A) The transcription factors DREB1 and DREB2 bind to dehydration-responsive elements (DRE) in the promoter of stress-responsive genes in an ABA-independent manner, not ABA-dependent. So, A is false with respect to ABA.
-
(B) ABA induces many genes such as LEA (Late Embryogenesis Abundant) proteins and RD29, which help plants respond to drought and stress. True.
-
(C) ABA-responsive genes contain ABRE (ABA-responsive element), a consensus six-nucleotide sequence motif, in their promoters that mediate transcriptional response to ABA. True.
-
(D) DRE (dehydration-responsive elements) are nine-nucleotide sequences present in promoters of certain ABA-responsive genes as well, integrating drought/cold responses. True.
Option-wise:
-
(1) A, B and C — A false.
-
(2) A, C and D — A false.
-
(3) B, C and D — all true.
-
(4) A only — A false.
Abscisic acid enhances plant stress tolerance by inducing expression of genes like LEA and RD29 through ABA-responsive ABRE promoter elements, while dehydration-responsive DRE elements also contribute; DREB transcription factors operate in ABA-independent pathways.
