Herbicide resistance in Convolvulus and Calystegia- a matter of GST activity?

摘要

Bindweeds are known to be problematic in agriculture with a certain ability to survive stress caused by electrophilic compounds which may function as herbicides. Glutathione S-transferases are enzymes involved in the detoxification of such organic xenobiotics. Thus, the activity of glutathione-S-transferases (GST) in stems, petals, rhizomes and leaves of hedge bindweed (Calystegia sepium) and field bindweed (Convolvulus arvensis) was investigated and compared by means of enzyme and inhibition assaysin order to examine GST contribution to detoxification of xenobiotics and herbicide tolerance. GST activity was high in both C. sepium and C. arvensis using model substrates CDNB and NBC, whilst DCNB and NBOC tests revealed significantly lower substrateaffinities. Glutathione reductase (GR) was active in both species, and high peroxidase (POX) activities were measured in perennial rhizomes with particularly high rates in C. arvensis, indicating that rhizomes are well equipped to withstand oxygen radical stress. Inhibition assays proved that except for one compound all the herbicidal substrates chosen were competitive to CDNB for GST affinity to various extents. Amongst the strategies C. arvensis and C. sepium plants employ to deal with xenobiotic stress, detoxifying GSTs as well as peroxidase and glutathione reductase were shown to belong to the most important ones.