1. Patterning the Arabidopsis fruit

2. Arabidopsis fruit structure
valve
margin
valve
replum

3. Arabidopsis fruit opening
valve
margin
seed
valve
replum

4. Fruit dehiscence promotes seed dispersal
valve
valve

5. Genes involved in seed dispersal in Arabidopsis can control loss of yield in oilseed crops

6. Note that DZ = Valve Margin

7. Genes Controlling Fruit Development? ? ?
replum
valve
margin
valve

8. SHATTERPROOF (SHP) gene is required for valve margin formation
wild type
shp

9. Genes Controlling Fruit Development?
SHP ?
replum
valve
margin
valve

10. IND and SHP are required for valve margin formation
wild type
ind
shp

11. wild type shp IND is expressed in stripes at the valve margin
and is positively regulated by SHP
valve margin
replum
valve
wild type
shp

12. ? ? Genes Controlling Fruit Development SHP IND replum valve margin

13. ? ? How is SHP and IND expression limited to the valve margin? SHP IND
replum
valve
margin
valve

14. FRUITFULL (FUL) transcription factor is required for valve cells
wild type
FUL is expressed
in valve cells
ful
wild
type

15. SHP and IND are ectopically expressed in ful mutant valves
Wild
type
valve
ful
mutant
IND expression

16. SHP and IND are negatively regulated by FUL in the valves
Wild
type
ful
mutant
IND expression

17. Is the fruitfull mutant phenotype caused by ectopic expression of the valve margin (SHP, IND) genes?

18. The failure of ful-mutant fruit to elongate is
restored by mutations in shp and ind
Wild type
shp ind ful
ind1 ful
shp ful
ful

19. The fruitfull mutant phenotype is caused by
mis-expression of SHP and IND
Wild type
shp ind ful
ind ful
shp ful
ful
“Valve” is the “default” state

20. ? FUL is expressed in valve cells where it functions
to negatively regulate SHP and IND
SHP
IND ?
FUL
replum
valve
margin
valve
enb

21. replumless (rpl) mutant fails to form a replum
Wild type
rpl
replum

22. RPL encodes a homeobox protein and is expressed in the replum

23. Are SHP and IND ectopically expressed in the rpl mutant replum?

24. IND is ectopically expressed in the rpl mutant replumVM VM R
wild type
rpl mutant
IND expression

25. Is the replumless mutant phenotype caused by the ectopic expression of the valve margin genes?

26. Mutations in SHP rescue rpl
Wild type
rpl
rpl shp

27. RPL is expressed in the replum and functions
to negatively regulated SHP and IND
SHP
IND
FUL
RPL
replum
valve
margin
valve

28. What happens in the ful rpl double mutant?
SHP
IND
FUL
RPL
replum
valve
margin
valve

29. All valve margin: rpl ful
replum
valve
valve
SHP and IND are expressed
In the valve, valve margin
and replum regions in
rpl ful mutants
rpl ful

30. Genes controlling fruit development?
SHP
IND
FUL
RPL
replum
valve
margin
valve

31. The FUL gene is normally expressed in valves
wild type
replum
valve
What happens if the FUL gene is
mis-expressed in all cells of the fruit?

32. mis-expression of FRUITFULL converts
replum and valve margin cells into valve cells
replum
valve
wild type
35S::FUL

33. D/V Signaling Is Required for Wing Margin Formation and Wing Outgrowth
Ap -> Notch -> Wing Margin
= D/V Organizer
D/V Organizer -> Margin Formation
and Wing Growth
Loss of ap in Dorsal Cells
-> Margin Formation
Activation of
Notch Along
Future Margin
ap - cells ap
Expressing Cells D
D ->V Signal V
V -> D Signal
ap Non-expressing
Cells
Wing imaginal disc in larva
Adult wing (viewed end on)
Adult wing with ap
- patch
Fig. 4.4

34. Interactions between cells on the dorsal and ventral
surfaces of leaves result in the formation of a leaf margin,
which is required for leaf outgrowth.

35. Phantastica mutants, like apterous mutants in flies,
cannot form the dorsal surface of leaves.

36. Loss of phantastica function leads to loss of leaf outgrowth.
Partial loss of phantastica function leads to narrow leaves
that are cupped upwards due to fewer dorsal cells.

37. Phantastica mutants illustrate that leaf outgrowth requires
interactions between dorsal and ventral cells.

38. Weak phantastica mutants can have “islands”
of ventral cells on the dorsal surface.
Marginal structures form at the border between
dorsal and ventral cells.

39. Conclusions
In flies and plants, juxtaposition of dorsal and ventral surfaces
induces formation of an organizing margin.
The organizing margin controls outgrowth of the appendage.