Wound response in mechanically isolated asparagus mesophyll cells: a model monocotyledon system

Cells at a wound surface in large organ explants are normally very difficult to study at the molecular level. We describe the use of mechanically isolated Asparagus mesophyll cell suspensions as alternative explants in which the majority of the cells are viable, damaged in a uniform manner and available in large numbers. Asparagus cells respond to wounding and to the culture medium by rapid cell expansion on day 3 post-isolation which precedes cell division by 24 h. Cell expansion was accompanied by a large rise in respiration rate and a massive increase in RNA synthesis; DNA content had only doubled by day 4. SDS-PAGE analysis of proteins showed that several polypeptides were absent, or present at a lower abundance, in 3-6-d-old wounded cells. Conversely, several novel polypeptides had appeared by this time which were not present in unwounded cladode; in particular, a large band at 16 kD was noted. Two dimensional PAGE analysis of protein translated in vitro using poly (A)+mRNA isolated from asparagus cells harvested at different times after wounding demonstrated that there was a major qualitative change in the message population and that much of the alteration in gene expression was probably controlled at the level of transcription. We believe that mechanically isolated asparagus cells provide a useful model system for the study of wound-induced cellular dedifferentiation and for the generation of wound-enriched mRNA populations.

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