Soybean seedlings were subjected to a wide range of physical (abiotic) or environmental stresses. Cloned cDNAs to heat shock (hs)-induced mRNAs were used to assess whether these diverse stresses induced the accumulation of poly(A)RNAs in common with those induced by hs. Northern blot hybridization analyses indicated that a wide range of stress agents lead to the accumulation of detectable levels of several of the hs-induced poly(A)RNAs; the relative concentration of those RNAs 'induced' by the wide range of stress agents (e.g. water stress, salt stress, anaerobiosis, high concentrations of hormones, etc.), was generally in the order of 100-fold lower than that induced by hs. There are two notable exceptions to that pattern of response to the stress agents. First, arsenite treatment resulted in accumulation of the 'hs poly(A)RNAs' to levels similar to those induced by hs. Cadmium also induced a somewhat normal spectrum of the 'hs poly(A)RNAs', but generally lower levels accumulated than in hs- and arsenite0treated tissues. Second, one set of poly(A)RNAs which are present at low and variable levels in control (non-stressed tissue) tissue, and which are increased some 5- to 10-fold by hs, increased in relative concentration in response to a wide range of the stress agents similarly to the response to hs. The physiological significance of the accumulation of this set of poly(A)RNAs (which translate into four electrophoretically different 27 kd proteins) is not known, but they certainly seem to serve as a monitor (or barometer) of physiological stress conditions. Cadmium treatment results in the accumulation of those same poly(A)RNAs and an additional band of higher molecular weight poly(A)RNA homologous to the same hs cDNA clone (clone pCE 54). Ethylene seems to have no obvious causal relationship to the hs response, even though hs-treated seedlings display some symptoms similar to those exhibited by ethylene-treated seedlings.

ABSTRACT1-Aminocyclopropane-l-carboxylate synthase (ACC synthase; S-adenosyl-L-methionine methylthioadenosine-lyase, EC 4.4

We have examined the effects of cytokinin, fusicoccin, and ethylene on auxin-induced changes in gene expression during auxin-promoted cell elongation in soybean (Glycine max L. Meff. cv Wayne) using cloned cDNAs to two auxin-responsive mRNAs (Walker, Key 1982 Proc Natl Acad Sci USA 79: . RNA blot analyses demonstrate that under conditions of cytokinin inhibition of auxin-promoted cell elongation the levels of these two auxin-responsive mRNAs is unaltered. Fusicoccinpromoted elonption is not associated with an enhanced expression of these two mRNAs, suggesting that the increased levels of these mRNAs observed during auxin-promoted cell elongation are not simply due to enhanced rates of cell elonption. We have also determined that ethylene plays no apparent role in the regulation of expression of these mRNAs. However, the auxins indole-3-acetic acid, 2,4-dichlorophenoxyacetic acid, and a-naphthalene acetic acid all enhance an accumulation of these mRNAs. We conclude that the regulation of these mRNAs is directly dependent on auxin. That auxin-promoted cell elongation is dependent upon the increased accumulation of these mRNAs remains to be determined.In recent years a considerable amount of evidence has accumulated indicating that all classes of plant hormones can cause selective changes in the levels of specific mRNAs (e.g. 3, 6, 8, 21). One system that has proven to be a useful model for studying the molecular mechanisms underlying hormonally induced changes in gene expression has been auxin-induced cell elongation (e.g. 12, 18, 23, 26 23, 25, and 50 uM, respectively (see 11 and references cited therein); FC was used at 10 JuM (see 14 and references cited therein); IPA was used at 50 uM (22). In experiments using ethylene, ethylene in air (10 ul/1) was gently bubbled into the incubation medium and allowed to exit through a second hole in the stoppered flask into 50% (v/v) ethanol. AVG was used at 100 ,M and ACC at 1 mM (9); all incubations using these compounds were performed in stoppered flasks. IAA, 2,4-D, a-NAA, IPA, AOA, and ACC were obtained from Sigma; AVG was a gift of W

Northern blot hybridization analyzes revealed that poly(A+) RNAs homologous to eight heat shock (HS)-specific cDNA clones were induced by arsenite (As) or Cd treatments. The mRNAs accumulated slower, and maximum accumulations were consistently lower than HS-induced levels. Prolonged treatment with low concentrations (50-100 micromolar) of As for 6 hours, or Cd for 12 hours, resulted in decreased accumulations of HS-specific mRNAs. This response resembled the 'autoregulation' observed during continuous 40°C HS. However, no autoregulation was evident when soybean seedlings were exposed to high concentrations of As (250 micromolar) or Cd (1 millimolar) for 12 hours. The cDNA probe pCE54 detected a second higher molecular weight poly(A+) RNA following As or Cd treatments which accumulated concomitantly with the lower molecular weight HS-specific poly(A+) RNA. The patterns of low molecular weight HS polypeptides from in vitro translations induced by HS, As, and Cd, and analyzed by one-dimensional and two-dimensional SDS-PAGE, were similar but temporal differences were apparent. In addition to HS proteins, many control proteins were also detected in both in vitro and in vivo labeling patterns from As and, to a lesser extent, Cd treatments. The chemical agents used in this study apparently induced the accumulation and translation of HS messages in vivo but not in the selective manner as observed during HS treatment.We have reported that the HS3 response in soybean seedlings can be elicited to some extent by various chemicals (4). Treatment with As or Cd results in the accumulation of some HSspecific poly(A+) RNAs to levels similar to those induced by HS. The synthesis of HS proteins is induced by As treatment and correlates with the development of a certain degree of thermotolerance in the soybean seedlings (16). Additionally, As or Cd treatment causes the induction of a second higher mol wt poly(A+) RNA not present in control and barely detectable in HS tissue which hybridizes to the cDNA probe pCE54.The addition of As or Cd to animal cell cultures can selectively enhance the synthesis of both specific poly(A+ ) RNAs and specific proteins which are similar, if not identical, to HS-induced

We determined the time course of increases in 1-aminocyclopropane-1-carboxylate (ACC) synthase activity in ripening tomato (Lycopersicon esculentum (L.) Mill.) pericarp discs following wounding and treatment with 75 mM LiCl. Over the course of 24 h, we detected oscillations in the amount of enzyme activity from an initial peak at 6 h to a subsequent, even higher level at 18 h. In-vitro translation products derived from poly(A)(+) RNAs isolated at various times of treatment and in-vivo-labeled proteins were immunoprecipitated using antibodies specific for ACC synthase. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography showed that wounding and treatment with LiCl induced an accumulation of translatable ACC-synthase-specific mRNAs. In addition, single, prominent bands were apparent for both in-vivo and in-vitro samples but their molecular masses differed. It appears that the in-vitro translation product is a polypeptide of 56 kDa while the in-vivo-labeled enzyme has a molecular mass of 47 kDa.