PLANT PHYSIOLOGY , Vol 114, Issue 3 917-925, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Modulation of Dehydration Tolerance in Soybean Seedlings (Dehydrin Mat1 Is Induced by Dehydration but Not by Abscisic Acid)
M. S. Whitsitt, R. G. Collins and J. E. Mullet
Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128
Germinated soybean (Glycine max L. cv Williams 82) seedlings subjected to
rapid dehydration begin to lose the ability to recover when the relative
water content of the plant decreases below 60%. The expanded cells of the
hypocotyl appear more susceptible to dehydration-induced damage than do
cells in the hypocotyl zone of cell growth. Pretreatment of seedlings prior
to rapid dehydration with nonlethal water deficit or exogenous abscisic
acid (ABA) shifts this viability threshold to progressively lower relative
water contents, indicating the acquisition of increased dehydration
tolerance. Increased tolerance is associated with osmotic adjustment in the
hypocotyl zone of cell growth and with increases in soybean dehydrin Mat1
mRNA levels. The accumulation of Mat1 mRNA is dehydration dependent but
insensitive to ABA. Induction of Mat1 mRNA accumulation by dehydration but
not by ABA makes it an unusual member of the dehydrin family.
