I. Heilmann et al., Transient dissociation of polyribosomes and concurrent recruitment of calreticulin and calmodulin transcripts in gravistimulated maize pulvini, PLANT PHYSL, 127(3), 2001, pp. 1193-1203
The dynamics of polyribosome abundance were studied in gravistimulated maiz
e (Zea mays) stem pulvini. During the initial 15 min of gravistimulation, t
he amount of large polyribosomes transiently decreased. The transient decre
ase in polyribosome levels was accompanied by a transient decrease in polyr
ibosome-associated mRNA. After 30 min of gravistimulation, the levels of po
lyribosomes and the amount of polyribosome-associated mRNA gradually increa
sed over 24 h up to 3- to 4-fold of the initial value. Within 15 min of gra
vistimulation, total levels of transcripts coding for calreticulin and calm
odulin were elevated 5-fold in maize pulvinus total RNA. Transcripts coding
for calreticulin and calmodulin were recruited into polyribosomes within 1
5 min of gravistimulation. Over 4 h of gravistimulation, a gradual increase
in the association of calreticulin and calmodulin transcripts with polyrib
osomes was seen predominantly in the lower one-half of the maize pulvinus;
the association of transcripts for vacuolar invertase with polyribosomes di
d not change over this period. Our results suggest that within 15 min of gr
avistimulation, the translation of the majority of transcripts associated w
ith polyribosomes decreased, resembling a general stress response. Recruitm
ent of calreticulin and calmodulin transcripts into polyribosomes occurred
predominantly in the lower pulvinus one-half during the first 4 h when the
presentation time for gravistimulation in the maize pulvinus is not yet com
plete.