Arabidopsis Thaliana

Question 1

Advantages of Arabidopsis Thaliana as a model organism

Answer 1

High seed yield, seeds easily stored and viable for years
Self-fertile
Short life cycle (6 Weeks)
Small Genome, Diploid, 5 chromosome pairs
Easily cultivated in a small space
Grows in many different environments

Question 2

How do plants determine when to flower?

Answer 2

Environmental Cues (Day length, temperature, the long cold period of winter)
Endogenous Cues (Hormones)
Arabidopsis Thaliana flowers in response to long days (facultative). The photoperiod is detected in the leaves.

Question 3

Circadian rhythms in Arabidopsis Thaliana

Answer 3

Circadian rhythms are controlled by a transcriptional negative feedback loop that establishes oscillations in gene expression programmes.

TOC1 is expressed in the evening and activates CCA1 and LHY at dawn - morning.

LHY/CCA1 repress TOC1 transcription in the light

Question 4

Florigen: The Hypothesised Hormone and Clock-Controlled Flowering Pathway

Answer 4

Light -> Circadian Clock -> CO -> FT and FD -> Floral Meristem Identity Genes (e.g. AP1)

Note: Light controls circadian clock AND acclivity of CO. Additionally, FT and FD physically interact and directly activate AP1 transcription.