post-translational regulation in plant development and abiotic...

Post-Translational regulation in plant development and abiotic stress

response

6-3-2009

Isabel Abreu

Stress

Signal perception

RESPONSE

Tolerance

Survival

Death

Regulating the regulator

Transcriptional Regulation

Alternative splicing– compartmentalization; functional differences

miRNA– leading to gene silencing

Phosphorylation – agonistic

SUMOylation – antagonistic

Mazucotelli et al. (2008) Plant Sci, 174:420

REGULATION

Post-Translational protein modifications (PTMs)

• PTMs result in an increase in complexity from genome to proteome

p.e. 30 000 give rise to 1.8M different protein species (human)

•Involved in protein regulation

•Often reversible, rapid, highly controlled and highly specific

•>300 types of PTMs have been described

•Only affect small percentage of total pool of specific protein



1. Phosphorylation – reversible attachment of a phosphate group to aa residue (most predominant covalent modification)

• 4 types: N-, S-, acyl-, and O-phosphorylation

• Usually in hydroxyl group of hydroxyamino acids (Ser, Thr,

Tyr)

• Protein kinases/Phosphatases (R-O-PO3)

• Highly dynamic process.

Nakagami et al. (2005) Trend Plant Sci, 10:339

Example of MAPKs

MAPKs are known to be activated by osmotic stresses in Medicago and tobacco;

Arabidopsis: MPK4 and MPK6 are activated by cold, salt, drought, wounding…

MPK3 can be activated by osmotic stress

MEKK1 is transcriptionally induced by salt, drought, cold and wounding

MKK2 is activated by cold and activates MPK4 and MPK6 –overexpression induces cold and salt tolerance and affects expression of 152 genes



2. S-nitrosylation – addition of NO to a Cys residue

• Role in NO signaling during biotic stress

• Probably as influential as phosphorylation

3. Glycosylation – covalent linkage of an oligosaccharide side chain to a protein

• N-X-S/T

• Starts co-translationally at ER

• Affects proteins involved in stress resistance



4. Ubiquitination – Covalent addition of Ubiquitin to target proteins

• Often requires phosphorylation

• Polyubiquitination: K48 for proteasome degradation; K63

activity modulation

• Monoubiquitination: leads to changes in localization and

activity

• DUBs are involved in Ubiquitin maturation, recycling and

reversibility.

Polyubiquitination

K63 ubiquitination is involved in

activity modulation

K48 ubiquitination targets proteins for proteasome degradation

UBIQUITINATION pathway

Ubiquitination and Abiotic Stress

• SDIR1 is a positive regulator of ABA signaling

• Up-regulation of SDIR1 enhances ABA-induced stomata closure, inducing drought tolerance

• sdir1-1 has ABA-insensitive phenotype and can be rescued by ABI5, ABF3 and ABF4

1. Regulation of ABA-dependent responses – involvement of RING-type E3 ligases

Ubiquitination and Abiotic Stress

• HOS1 negatively controls cold-stress response

• Promotes degradation of master cold-response regulator: Inducer of CBF Expression 1 (ICE1)

2. Regulation of cold-stress response – involvement of RING-type E3 ligases

HOS1 ICE1Cold-responsive

genes

RUB1: activation and

destabilization of SCF complexes,

transcriptional regulation of p53

HUB1: Pre-mRNA splicing2 targets identified in yeast

ATG8/12: Autophagy, nutrient

recycling in plants

Ub: protein degradation,

localization, protein interaction

Post-translational protein modification by small Ub-like

proteins

UFM1: function unknown

-grasp fold

Diversity in functions for sumoylation

Chromosome segregation

Cell division

DNA replication and repair

Nuclear protein import (RanGAP1)

Protein targeting to

subnuclear structures

Ubiquitination Antagonist

…

Regulation of

inflammatory response

in mammals

Overall, SUMO modifies the activity of proteins; modifies their ability to

interact with other proteins; and modifies their subcellular localization

SUMO

SUMO modification pathway

Novatchkova et al. Planta. 2004;220:1-8

Tempe et al. (2008) Biochem Soc Trans, 36:874

75

150

250

100

50

0 0.5 2 0.5 2 0.5 2 0.5 2 0.5 2 2 4 (h)

control H/S NaCl EthH2O2 Deh

• Several types of abiotic stress

induce sumoylation:

•Heat Shock (37°C);

•50mM H2O2;

•7% ethanol;

•Dehydration

SUMOylation and the response to Abiotic Stress

AP anti-SUMO1

SUMOylation and the response to Drought

SIZ1 (E3 ligase) dependency:

Catala et al. (2007) Plant Cell, 19:2952

SIZ1 has a role in drought tolerance

siz1 is more sensitive to drought

stress.

What about plant size?


siz1:

Significantly smaller than WT plants

Deficiencies in leaf elongation and enlargement

siz1 is affected in growth

Smaller epidermal and mesophyll cells



siz1 is more sensitive to drought

stress.



siz1 seedlings loose water faster than WT


Transcriptome analysis of siz1

Among the ~1700 drought-inducible genes, 262 are positively regulated by SIZ1.

• Not involved in ABA-independent drought response pathways (DREB2A & ERD1)

• Needed for basal expression of ABA-dependent genes involved in drought response

• Role in regulation of anthocyaninbiossintetic pathway

• Role in regulation of of expression of several enzymes involved in hormone biosynthetic pathways (brassinosteroids; jasmonate)


Diverse functions of sumoylation

Chromosome segregation

Cell division

DNA replication and repair

Nuclear protein import (RanGAP1)

Protein targeting to

subnuclear structures

Ubiquitination Antagonist

…

…

SUMO

Mediates stress response (SIZ1):

•General Sumoylation (ABA

independent)

•Regulates ABA dependent drought-

stress response

Mazucotelli et al. (2008) Plant Sci, 174:420

UBC9 Example

• Ubiquitination: 10 E1 + 100 E2 + 1000 E3• SUMOylation: 1 E1 + 1 E2 + <10 E3

UBC9

How is regulation done?

Knipscheer et al. (2008) Mol Cell, 31:371

UBC9 Example

Knipscheer et al. (2008) Mol Cell, 31:371

ICE1 Example

• ICE1 is constitutively expressed• Activates CBF genes expression upon cold stress only• Is important for cold tolerance

ICE1 Example

• ICE1 is constitutively expressed• Activates CBF genes expression upon cold stress only

Miura et al. Plant Cell, 19:1403

ICE1 Example



SUMOylation induces CBF activation by ICE1

ICE1 Example



SUMOylation induces CBF activation by ICE1Ubiquitination leads to ICE1 degradation

ICE1 Example


Phosphorylation


SUMOylation induces CBF activation by ICE1Ubiquitination leads to ICE1 degradation

ICE1 Example


Phosphorylation


SUMOylation induces CBF activation by ICE1Ubiquitination leads to ICE1 degradationPhosphorylation can induce SUMOylation

ICE1 Example


Phosphorylation


SUMOylation induces CBF activation by ICE1Ubiquitination leads to ICE1 degradationPhosphorylation can induce SUMOylationHOS1 phosphorylation upon cold stress leads to nuclear import (?)

ICE1 Example


Phosphorylation


Complex interplay between post-translational protein modification in transcriptional control

post-translational regulation in plant development and abiotic...

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