TIR (Toll/interleukin-1 receptor/resistance protein) domains are cytoplasmic domains widely found in animals and plants, where they are essential components of the innate immune system. A key feature of TIR-domain function in signaling is weak and transient self-association and association with other TIR domains. An additional new role of TIR domains as catalytic enzymes has been established with the recent discovery of NAD+-nucleosidase activity by several TIR domains, mostly involved in cell-death pathways. Although self-association of TIR domains is necessary in both cases, the functional specificity of TIR domains is related in part to the nature of the TIR : TIR interactions in the respective signalosomes. Here, we review the well-studied TIR domain-containing proteins involved in eukaryotic immunity, focusing on the structures, interactions and their corresponding functional roles. Structurally, the signalosomes fall into two separate groups, the scaffold and enzyme TIR-domain assemblies, both of which feature open-ended complexes with two strands of TIR domains, but differ in the orientation of the two strands. We compare and contrast how TIR domains assemble and signal through distinct scaffolding and enzymatic roles, ultimately leading to distinct cellular innate-immunity and cell-death outcomes.
Ralstonia solanacearum
is a harmful pathogen that causes severe wilt disease in several vegetables. In the present study, we identified
R. solanacearum
from wilt of papaya by 16S rRNA PCR amplification. Virulence ability of
R. solanacearum
was determined by amplification of approximately 1500 bp clear band of
hrpB
gene. Further,
in-vitro
seed germination assay showed that
R. solanacearum
reduced the germination rate up to 26.21%, 34% and 33.63% of cucumber, bottle guard and pumpkin seeds, respectively whereas shoot and root growth were also significantly decreased. Moreover, growth inhibition of
R. solanacearum
was recorded using antibacterial compound from medicinal plant and antagonistic
B. subtilis.
Petroleum ether root extract of
Rauvolfia serpentina
showed highest 22 ± 0.04 mm diameter of zone of inhibition where methanolic extract of
Cymbopogon citratus
and ethanolic extract of
Lantana camara
exhibited 20 ± 0.06 mm and 20 ± 0.01 mm zone of inhibition against
R. solanacearum
, respectively
.
In addition, bioactive compounds of
B. subtilis
inhibited
R. solanacearum
growth by generating 17 ± 0.09 mm zone of inhibition. To unveil the inhibition mechanism, we adopted chemical-protein interaction network and molecular docking approaches where we found that, rutin from
C. citratus
interacts with citrate (Si)-synthase and dihydrolipoyl dehydrogenase of
R. solanacearum
with binding affinity of −9.7 kcal/mol and −9.5 kcal/mol while quercetin from
B. subtillis
interacts with the essential protein F0F1 ATP synthase subunit alpha of the
R. solancearum
with binding affinity of −6.9 kcal/mol and inhibit the growth of
R. solanacearum
. Our study will give shed light on the development of eco-friendly biological control of wilt disease of papaya.
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