Isolation of active DNA-binding nuclear proteins from tomato galls induced by root-knot nematodes

Abstract

We describe 2 methods for extraction of DNA-binding proteins from root-knot nematode feeding sites (ie, galls). DNA-binding activity was assayed by electrophoretic mobility shift assays using fragments from the root-knot nematode-responsiveLEMMI9 and 35S promoters. In noninfected tissue, the method based on nuclei enrichment through a Percoll cushion was superior for isolation of DNA-protein binding activity with both promoters. With infected roots; the method based on crude extracts performed better with theLEMMI9 promoter, whereas nuclei-enriched extracts worked better with the 35S promoter. Therefore, both methods can be used to extract proteins for DNA-binding assays from infected roots, but the method of choice may depend on the promoter under study.