Abstract:
The Arabidopsis NPRI protein regulates systemic acquired resistance dependent on
salicylic acid. Analyses by plant two-hybrid analysis in vivo and pull-down assays in
vitro showed that the BTB/POZ domain of NPRI at the N-terminus serves as an
autoinhibitory domain to negate the function of the transactivation domain at the
C-terminus through direct binding of these two domains. I t was also shown that the
binding of the BTB/POZ domain to the C-terminus of NPRI was abolished by SA
treatment, suggesting that SA could interfere directly with this binding. By gel
filtration, it was demonstrated that SA affects the conformation of full-length NPRl ,
confirming the role of NPRI as an SA receptor. Gel filtration analysis also indicated
that NPRI could be converted from an oligomer to a dimer with SA treatment.
Furthermore, one N-terminal deletion ~513 has been shown to act as a metal-binding
protein and its two Cys-521 and Cys-529 are important for binding to Ni
2
+ by
pull-down assays.
