|Ph.D Student||Ben-Naim Orna|
|Subject||Induction of Flowering by Light in Tomato: The Role of the|
CONSTANS System in Day-Neutral Plants
|Department||Department of Biology||Supervisor||Professor Emeritus Eliezer Lifschytz|
The transition from the vegetative to the reproductive phase is a major developmental event in plants. The process involves the transformation of the shoot meristem to an inflorescence meristem and it depends on the ability of the plant to decode environmental and endogenous signals.
In Arabidopsis, a model plant with monopodial shoots the transition to flowering is promoted by long days and occurs only once. The tomato however is a day-neutral plant with reiterated alternation of the vegetative/reproductive phases.
To understand the role of the light signaling machinery of Arabidopsis in the day-neutral tomato we have initiated the analysis of the tomato CONSTANT genes.
My thesis describes first the unique genomic organization and coding sequences of three tomato CO (TCO) genes. Coding sequences were subsequently used to show that the TCO1 and TCO3 genes are regulated, just like their counterparts of Arabidopsis, by both the diurnal cycle and the circadian clock. The T-FT gene a known target of CO does not respond however to diurnal changes under long day conditions.
To understand the molecular function of CO genes I have isolated by virtue of the two-hybrid screen, four TCO interacting proteins (TCIPs). Two TCIPs interact with the N-terminal B-Box of TCO while two other with the C-terminal, CCT domain. Interactions were verified in vitro and in planta and with the exception of TCIP3 identical associations were observed with the CO protein of Arabidopsis.
A model incorporating TCIPs into a complex that may regulate CO target genes is presented and its implications discussed.