Patterning the Arabidopsis fruit
Jan 23, 2016
Patterning the Arabidopsis fruit
Arabidopsis fruit structure
replum
valvemargin
valve
valve
valvemargin seed
Arabidopsis fruit opening
replum
Fruit dehiscence promotes seed dispersal
valvevalve
Genes involved in seed dispersal in Arabidopsis can control loss of yield in oilseed crops
Genes involved in seed dispersal in Arabidopsis can control loss of yield in oilseed crops
StigmaStyle
OvaryValveReplum
SeedDehiscenceZone (DZ)
DehiscenceZone (DZ)
Replum
Valve
Note that DZ = Valve Margin
Genes Controlling Fruit Development
replum
valvemarginvalve
?
?
?
wild type shp
SHATTERPROOF (SHP) gene is required for valve margin formation
Genes Controlling Fruit Development
replum
valvemarginvalve
?
?
SHP
wild type ind shp
IND and SHP are required for valve margin formation
IND is expressed in stripes at the valve margin and is positively regulated by SHP
wild type shp
replum valvevalve margin
Genes Controlling Fruit Development
replum
valvemarginvalve
?
?SHP
IND
How is SHP and IND expressionlimited to the valve margin?
replum
valvemarginvalve
SHPIND
??
FRUITFULL (FUL) transcription factor is required for valve cells
ful
Valve cells
FUL is expressedin valve cells
fulwild type
wildtype
SHP and IND are ectopically expressed in ful mutant valves
fulmutant
Wild type
IND expression
valve
valve
SHP and IND are negatively regulatedby FUL in the valves
fulmutant
Wild type
IND expression
Is the fruitfull mutant phenotype caused by ectopic expression of the valve margin (SHP, IND) genes?
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
The fruitfull mutant phenotype is caused bymis-expression of SHP and IND
Wild type
shp ind ful
ind ful
shp ful
ful
“Valve” is the “default” state
FUL is expressed in valve cells where it functionsto negatively regulate SHP and IND
replum
valvemarginvalve
enb
SHPIND ?FUL
replumless (rpl) mutant fails to form a replum
replumreplum
rplWild type
RPL encodes a homeobox protein and
is expressed in the replum
RPL
Are SHP and IND ectopically expressed in the rpl mutant
replum?
IND is ectopically expressedin the rpl mutant replum
IND expression
rpl mutant
wild type
VM VM
R
Is the replumless mutant phenotypecaused by the ectopic expression
of the valve margin genes?
Mutations in SHP rescue rpl
Wild type rpl rpl shp
RPL is expressed in the replum and functions to negatively regulated SHP and IND
replum
valvemarginvalve
SHPIND
RPLFUL
What happens in the ful rpl double mutant?
replum
valvemarginvalve
SHPIND RPLFUL
All valve margin: rpl ful
rpl ful
SHP and IND are expressed In the valve, valve margin
and replum regions inrpl ful mutants
valve replum valve
Genes controlling fruit development?
replum
valvemarginvalve
SHPIND RPLFUL
What happens if the FUL gene ismis-expressed in all cells of the fruit?
wild type
replum
valve
The FUL gene is normally expressed in valves
mis-expression of FRUITFULL converts replum and valve margin cells into valve cells
wild type 35S::FUL
replum
valve
D ->V Signal
V -> D Signal
ap Expressing Cells
ap Non-expressing Cells
D
V
Activation ofNotch AlongFuture Margin
Ap -> Notch -> Wing Margin = D/V Organizer
D/V Signaling Is Required for Wing Margin Formation and Wing OutgrowthD/V Organizer -> Margin Formationand Wing Growth
ap - cells
Wing imaginal disc in larva Adult wing (viewed end on) Adult wing with ap- patch
Loss of ap in Dorsal Cells -> Margin Formation
Fig. 4.4
•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.
Phantastica mutants, like apterous mutants in flies, cannot form the dorsal surface of leaves.
•Loss of phantastica function leads to loss of leaf outgrowth.
•Partial loss of phantastica function leads to narrow leavesthat are cupped upwards due to fewer dorsal cells.
•Phantastica mutants illustrate that leaf outgrowth requiresinteractions between dorsal and ventral cells.
•Weak phantastica mutants can have “islands” of ventral cells on the dorsal surface.
•Marginal structures form at the border betweendorsal and ventral cells.
•In flies and plants, juxtaposition of dorsal and ventral surfaces induces formation of an organizing margin.
•The organizing margin controls outgrowth of the appendage.
Conclusions