Discussion
Consider the following four experimental observations (i, ii, iii, iv) on the effect of the FT gene on flowering transition in the shoot apical meristem (SAM) of Arabidopsis thaliana.
i) The FT promoter is active in leaves alone.
ii) The ft null mutation causes delayed flowering transition of the SAM.
iii) Expressing a recombinant FT protein fused to nuclear localization signal sequence under the endogenous promoter does not rescue the delayed-flowering phenotype of the ft null mutant.
iv) Downregulation of FT transcript in the SAM by RNA interference in the wild-type background does not alter flowering transition.
Which one of the following conclusions best explains the above observations?
Answer: C
The best conclusion is that FT protein moves from leaves to the SAM and promotes flowering.
Observation (i) shows FT is made only in leaves, yet (ii) shows it is needed for the apex to flower, so something must travel from leaf to apex. (iii) shows that trapping the protein in leaf nuclei (with a nuclear localisation signal) stops it working, so the protein must leave the leaf cells. (iv) shows that destroying any FT transcript in the meristem has no effect, so the mRNA is not what acts there.
Together these point to the FT protein as the mobile florigen. A leaf-resident protein is ruled out by (iii), a mobile transcript by (iv), and a requirement for both in the SAM is ruled out by (iv) as well.
Post your comment
Please log in or register to post a comment.
Examination Categories
- SSC Exams
- Banking Exams
- Teaching Exams
- Civil Services Exams
- Railways Exams
- Engineering Recruitment Exams
- Defence Exams
- State Government Exams
- Police Exams
- Insurance Exams
- Nursing Exams
- Other Government Exams
- NRA CET
- PG Entrance Exams
- Campus Placement
- MBA Entrance Exams
- CUET and UG Entrance
- Judiciary Exams
- Regulatory Body Exams
- Software Development