This document discusses the role of TOR kinase as a regulator that switches plants between stress response and growth. It finds that TOR phosphorylates PYLs, preventing them from activating stress responses when stress is absent. It also finds that under stress, the stress-activated SnRK2 kinase phosphorylates Raptor B to repress TOR activity and prevent growth. This allows plants to conserve energy and ensure survival during unfavorable conditions. The phosphorylation of PYLs can also shut off ABA signaling during stress recovery.

1. To Grow or Not to Grow: A long and winding
sTORy
Presented by,
Shreya Mandal
21104
M.Sc. 2nd year
2018-20

2. Rapa was found in Easter Island
Most isolated island in the world
Located about 2400 km from both Tahiti and
Chile
 Today, the land, people, and language is
referred as “RAPA NUI”
 Introduction
Rapa Nui- Island flag

3.  The History of TOR Inhibitors
1969: Soil samples containing Streptomyces
hygroscopicus collected on Easter Island
1972: Rapamycin identified as an
excretory product of S. hygroscopicus
1973: Rapamycin identified as anti proliferative
1977: Rapamycin activity in animal models
of autoimmune disease demonstrated
1988: Rapamycin identified as immunosuppressant in experimental
studies
1999: Rapamycin
received FDA approval
Suren Sehgal and his team

4. TOR Kinase - evolutionary conserved
master regulator

5. mTORC1/ AtTORC1
mTORC2
mTOR - core
component of two
distinct protein
complexes

6.  ABA - stress signals and stress responses
Osmotic Stress
ABA
RCAR/PYR1/PYL
RCAR/PYR1/PYL
ABA
SnRK2
SnRK2
group III
P
Clade A
PP2C
TF
s
P
Gene
expression
Stomatal
Closing
Response

7.  TOR- a potential regulator of switch between
the stress response and growth
TOR RaptorLST8
Autophagy
S6K1/2BIN2
BZR1
RPS6
eIF3h
E2Fa/b
PYLs
BR signalling
Hypocotyl
elongation
Translation
Greening
Flowering
Cell cycle
Meristem
activation
ABA signalling
Seed
germination
Growing

9. Generation of the es-tor Mutant
Germination /Growth under
ABA / Mannitol treatment
Measurement of Chlorophyll ContentIn-gel Kinase Assay
In-vitro Kinase Assays ,
Immunoprecipitation TOR Kinase Assays
ABA binding Assay
Phosphatase Activity Assay
RNA Extraction
and Real Time PCR
Electrolyte Leakage Assay
Protein Extraction
and Digestion
 Methods

10.  Results 1. Phosphorylation of PYLs at a Conserved
Serine Residue Abolishes Their Activity
a.
b.
c.

11.  Results
2. Phosphomimic Mutations of Ser119 in PYLs Inhibit ABA Binding

12.  Contd.

13.  Results 3. TOR Kinase Phosphorylates PYLs and
Negatively Regulates ABA Signalling in
the Absence of Stress

14.  Contd.

15.  Results 4. ABA Represses TOR Kinase Activity through
SnRK2 –Mediated Phosphorylation of Raptor B

16. CONCLUSION

17.  SUMMARY
 TOR phosphorylation of PYLs prevents activation of stress
responses when stress is absent.
 Raptor phosphorylation by stress- and ABA- activated SnRK2 is a
mechanism that prevents plant growth under unfavourable
conditions to conserve energy and ensure survival.
 The phosphorylation of PYLs can also switch off ABA signalling
during stress recovery in plants.

18.  Path Ahead
 These findings suggest a role of SnRK2s in reprogramming
translation in response to ABA and osmotic stress.
 The inhibition of TOR may also cause impairment of auxin
signalling.(Li et al., 2017).
 The DELLA family of growth inhibitory nuclear proteins play
important roles in mediating growth inhibition by salt stress,
ABA, and ethylene. Future research will determine how ABA
inhibition of TOR kinase may be coordinated with the stabilization
of DELLA proteins to inhibit plant growth during stress.