Cg. Downs et Sd. Somerfield, ASPARAGINE SYNTHETASE GENE-EXPRESSION INCREASES AS SUCROSE DECLINES IN BROCCOLI AFTER HARVEST, New Zealand journal of crop and horticultural science, 25(2), 1997, pp. 191-195
Broccoli (Brassica oleracea L.) floral tissues rapidly differentiate a
nd grow before harvest and then senesce rapidly after harvest. The fac
tors regulating this rapid postharvest senescence are currently under
investigation. We show that within 6 h of harvest sucrose concentratio
n in florets declines by c. 50%, and between 24 and 72 h asparagine le
vels increase more than 7-fold. This increase in asparagine parallels
an earlier increase in asparagine synthetase (AS) gene expression in f
lorets. Northern analyses show that AS transcript abundance increases
from 2 to 24 h after harvest, and then declines. AS transcript abundan
ce also increases in harvested leaves as they turn yellow, although to
a level lower than that seen in florets. In other plant systems, incl
uding asparagus, increases in AS gene expression occur as a result of
a decline in sucrose status. We note the considerable similarities bet
ween broccoli and asparagus postharvest physiology and discuss our res
ults for broccoli AS in terms of possible regulation by sucrose status
.