PhD defence: The nuts and bolts of stem elongation

Thesis by S.S. Silva MSc

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Close to half of vegetables produced worldwide is derived from rosette crops, like lettuce, cabbage and beets. Characteristically, these plants form rosettes (a compact whorl of leaves) later followed by formation of a stem (bolting). Bolting ends rosette growth and ruins a rosette crop, thus the rosette is agriculturally important for many vegetables. However, we do not know how the rosette is formed and how rosette plants switch from compact to elongation growth when bolting.

In this thesis we investigated both processes in the model plant Arabidopsis thaliana. We show that the ARABIDOPSIS THALIANA HOMEOBOX 1 (ATH1) gene is crucial for forming a proper compact rosette. When Arabidopsis forms its rosette, ATH1 is present in the above-ground control centre of the plant (shoot apex), but ATH1 disappears from there during bolting. Mutants lacking ATH1 do not form compact rosettes, but instead form stem tissue between rosette leaves as if the plant is bolting in the wrong developmental stage. We called this phenomenon “heterochronic bolting”. These plants are extra sensitive to environmental and hormonal growth signals, sometimes even losing their rosette architecture altogether. Plants that artificially produce ATH1 during their entire lifespan never bolt, not even in the presence of bolting-inducing signals. We concluded that, as long as ATH1 is active in the shoot apex, important growth signals are blocked by ATH1, rosette growth is stimulated and bolting is prevented.

Our findings shine light on two poorly studied processes in plant biology and could be used for the development of bolting resistant rosette crops.

Start date and time
End date and time
Location
University Hall, Domplein 29
PhD candidate
S.S. Silva MSc
Dissertation
The nuts and bolts of stem elongation - Unravelling the role of ARABIDOPSIS THALIANA HOMEOBOX 1 in the control of the Arabidopsis rosette habit
PhD supervisor(s)
prof. dr. J.C.M. Smeekens
Co-supervisor(s)
dr. M.C.G. Proveniers