Patterning the Arabidopsis fruit

Arabidopsis fruit structure valve margin valve replum

Arabidopsis fruit opening valve margin seed valve replum

Fruit dehiscence promotes seed dispersal valve valve

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

Note that DZ = Valve Margin

Genes Controlling Fruit Development ? ? ? replum valve margin valve

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

Genes Controlling Fruit Development ? SHP ? replum valve margin valve

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

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

? ? Genes Controlling Fruit Development SHP IND replum valve margin

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

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

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

SHP and IND are negatively regulated by FUL in the valves Wild type ful mutant 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 by mis-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 functions to negatively regulate SHP and IND SHP IND ? FUL replum valve margin valve enb

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

RPL encodes a homeobox protein and is expressed in the replum

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

IND is ectopically expressed in the rpl mutant replum VM VM R wild type rpl mutant IND expression

Is the replumless mutant phenotype caused 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 SHP IND FUL RPL replum valve margin valve

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

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

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

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?

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

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

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 leaves that are cupped upwards due to fewer dorsal cells.

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

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

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.