PLANT PHYSIOLOGY , Vol 105, Issue 3 823-830, Copyright © 1994 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Effects of Abscisic Acid Metabolites and Analogs on Freezing Tolerance and Gene Expression in Bromegrass (Bromus inermis Leyss) Cell Cultures
A. J. Robertson, MJT. Reaney, R. W. Wilen, N. Lamb, S. R. Abrams and L. V. Gusta
Crop Development Centre, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 0W0, Canada (A.J.R.,M.J.T.R., R.W.W., L.V.G.)
Optical isomers and racemic mixtures of abscisic acid (ABA) and the ABA
metabolites abscisyl alcohol (ABA alc), abscisyl aldehyde (ABA ald),
phaseic acid (PA), and 7[prime]hydroxyABA (7[prime]OHABA) were studied to
determine their effects on freezing tolerance and gene expression in
bromegrass (Bromus inermis Leyss) cell-suspension cultures. A dihydroABA
analog (DHABA) series that cannot be converted to PA was also investigated.
Racemic ABA, (+)-ABA, ([plus or minus])-DHABA, and (+)-DHABA were the most
active in inducing freezing tolerance, (-)-ABA, ([plus or
minus])-7[prime]OHBA, (-)-DHABA, ([plus or minus])-ABA ald, and ([plus or
minus])-ABA alc had a moderate effect, and PA was inactive. If the relative
cellular water content decreased below 82%, dehydrin gene expression
increased. Except for (-)-ABA, increased expression of dehydrin genes and
increased accumulation of responsive to ABA (RAB) proteins were linked to
increased levels of frost tolerance. PA had no effect on the induction of
RAB proteins; however, ([plus or minus])- and (+)-DHABA were both active,
which suggests that PA is not involved in freezing tolerance. Both (+)-ABA
and (-)-ABA induced dehydrin genes and the accumulation of RAB proteins to
similar levels, but (-)-ABA was less effective than (+)-ABA at increasing
freezing tolerance. The (-)-DHABA analog was inactive, implying that the
ring double bond is necessary in the (-) isomers for activating an ABA
response.
