Sa. Harding et Ac. Smigocki, CYTOKININS MODULATE STRESS-RESPONSE GENES IN ISOPENTENYL TRANSFERASE-TRANSFORMED NICOTIANA-PLUMBAGINIFOLIA PLANTS, Physiologia Plantarum, 90(2), 1994, pp. 327-333
The effects of transiently elevated cytokinin levels on gene expressio
n following stress were examined in transgenic Nicotiana plumbaginifol
ia plants. Plants were transformed with a bacterial gene encoding isop
entenyl transferase (ipt) cloned behind the heat shock (HS) protein 70
promoter from Drosophila melanogaster. Following a 1-h, 45-degrees-C
HS of whole plants, the ipt transcript levels in leaves increased 30-
to 40-fold. Analysis of in vitro translation products of leaf messenge
r RNA showed rapid isopentenyl transferase-dependent changes in gene e
xpression. A subset comprising 1 to 2% of resolvable translation produ
cts was specifically up-regulated in heat shock ipt-inducible (HS-ipt)
plants. Several cDNA clones were isolated which correspond to mRNAs t
hat are up-regulated 2- to 4-fold in HS-ipt plants. Two of the cDNAs e
ncode stress-related polypeptides, one a member of a class of small he
at shock polypeptides (HSP) and the other, a wound-inducible glycine-r
ich protein. Benzylaminopurine feeding experiments show that the HSP t
ranscripts are up-regulated by other treatments including watering but
that cytokinins strongly accelerate or amplify the response. These da
ta are the first to show altered modulation of stress-induced genes in
intact plants transformed with the cytokinin biosynthesis gene ipt.