Repair and regeneration Injury program includes: Injury program New organ initiation Primordium activation (dormant buds) Vascular repair Abscission Damage.

Repair and regeneration

Injury program includes:

Injury program

New organ initiation

Primordium activation (dormant buds)

Vascular repair

Abscission

Damage control

Primary signalsO2

C2H4

Δ [IAA]

Δ [CK]

MeJ or SA

• Response to injury is local &/or systemic

Phenylalanine

Cinnamic acid

Cinnamyl CoA

Chalcone

Flavonoids

Phytoalexins

Ferulic acid

PAL

Chalcone synthase

aa+

+

Oligos

C2H4

MeJ

SA

Suberin

Lignin

IAA transport

Wall crosslinks

+

+

-

+

+

Proteinase inhibitors

Chitinase

Systemic = upregulation of PAL and chalcone synthase Damage control, ‘immune’ response in whole body

Local response might involve vascular repair

Cork forms over injury

Parenchyma cells de-differentiate procambium vascular tissue– Dedifferentiation doesn’t occur until vasculature is broken

– IAA and CK activate dedifferentiation

Local response may include organ replacement

Dormant primordia released– Leaf– Axillary/lateral buds

• Stem primordia

– Root

Root external view of primordia

Hormones affect apical dominance;injury to SAM or RAMStem

IAA apical dominance

CK made in rootsCK axillary/lateral bud growth

What happens if herbivore removes SAM?

RootCK Root Apical dominance

What happens if something chomps on root tip?

+ IAA

IAA-

CK

++

+

+

++

Applying what we knowCuttings of stems, tubers, corms

– Hybrids– Seedless plants

Tissue culture– Orchids; transgenic species;nursery species

How do we regenerate organs? Injury causes:

Parenchyma cells to dedifferentiate callus

Hormone concentrations to changeRelative [IAA] : [CK] important Higher [IAA] promotes root program Higher [CK] promotes stem program

Callus CK

Root program

Shoot program

IAA

+

+

-

-

How else do we apply what we know?Injury, moisture and darkness

– Layering– Grafting