Elucidating the involvement of inositol compounds in protein expression and stability
Student name: Ms Aashna Khosla
Guide: Dr Ramakrishnan Sitaraman
Year of completion: 2014
Host Organisation: UNESCO- Regional Centre for Biotechnology, Gurgaon, Haryana
Supervisor (Host Organisation): Dr Saikat Bhattacharjee
Abstract: Plant growth and reproduction is threatened by many pathogens and pests. Plant
responds to such infestation using two-branched innate immune system. The first
branch that recognizes and responds to molecules common to many classes of
microbes is known as PAMP triggered immunity. The second class known as
effector triggered immunity (ETI) responds to pathogen virulence factors, either
directly (Receptor-ligand Model) or through their effects on host targets (Guard
Model/Decoy Model). Host adapted pathogens bypass PRR-triggered defences by
delivering certain virulence factors known as effectors to cause disease. However,
virulent pathogens encounter an important post infection resistance layer (basal
resistance) controlled by, among others, the nucleocytoplasmic lipase-like protein
ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1). Several studies have been
carried out on EDS1, its structure or its role in cell signalling, its presence has been
strongly felt in plant cell immunity. EDS1 is an indispensable component of effector
-triggered immunity. It is also structurally different from other putative plant lipases.
Hence, EDS1 expression and structural analysis would clarify its role in plant
immunity. It is known that EDS1 homodimer exist, hence, deciphering EDS1
structure would be an important step towards unravelling its role in plant resistance
mechanism. An attempt to crystallize EDS1 hasn‟t been successful because of its
instability over time in isolation process. Biotic stress in plants has shown
perturbations in expression profiles of inositols. It is therefore pertinent and
necessary to understand the role of inositol in mediating defence responses in plants
post pathogen infestation. The present work involves elucidating the involvement of
inositol compounds in EDS1 expression and stability. This investigation involves
protein expressions in heterologous hosts and determining relative changes in
expression levels and stability upon addition of various inositol and higher
phosphates. The expression levels and stability of EDS1 were checked in BL21 AI
strain of E.coli induced in the presence of myo-inositol and phytic acid (inositol
hexakisphosphate). Genetic studies have shown that plants mutated for ipk1 (inositol
1,3,4,5,6-pentakisphosphate 2-kinase) are stunted. Hence IPK1 is a negative
regulator of immunity. Surprisingly, plants homozygous for ipk1 eds1 double
mutations shows wild type phenotype. This suggests a preliminary genetic link
between the two. So, link needs to be analyzed at the molecular level for any direct
v
interaction between them. Hence, dual expression of IPK1 and EDS1 was attempted
to know using purification studies for any direct interaction between them.
KEYWORDS:-
PTI, ETI, Guard model, Decoy model, myo-inositol, phyticacid , IPK1, EDS1
