Microanalysis of free amino acids in the aseptic host-parasite system: Ficus carica-Xiphinema index (nematoda)

Abstract

Fig ( Ficus carica) is a host of the ectoparasitic root nematode Xiphinema index. In culture X. index caused attacked root-tips of F. carica seedlings to swell and finally to become transformed into terminal galls. Cells at feeding sites within attacked root-tips became multinicleate and showed features of high metabolic activity. For the analysis of changes in the free amino acids in the aseptic host-parasite interaction, a microchromatographic method was applied, using a computerized fluorescence scanning photometer for the evaluation of dansylated substances. This method was so sensitive that it allowed the detection of free amino acids in a few root-tips and even in single root-tip galls, as well as in batches of 15 nematodes (females) and in dissected body parts, such as basal oesophageal bulbs which contain a very active, large secretory dorsal gland cell. Changes in the free amino acids in root-tips were quantified by this method at about 10 −12 mol, using calibration curves. The results were compared with those obtained from an automatic analyser (using many root-tips) and were found to be very reliable. Pronounced changes occurred in the levels of some amino acids, especially glutamic acid (increase) and glycine (decrease), during the formation of root-tip galls and modified cells. Glycine dominated in the oesophageal bulbs of feeding nematodes, but was most probably not injected into attacked root-tips. Unknown dansylated substances which showed distinct differences between root-tip galls and control root-tips as well as between fed and unfed nematodes also were recorded.