An Analysis of Growth Regulator Interactions and Gene Expression during Auxin-Induced Cell Elongation Using Cloned Complementary DNAs to Auxin-Responsive Messenger RNAs

Abstract

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

Indole-3-acetic acid and fusicoccin cause cytosolic acidification of corn coleoptile cells

“…Changes in transmembrane ion gradients brought about by pump stimulation could act, like free Ca2+, as a second messenger (20,40) and influence processes such as secretion, protein synthesis, and gene transcription (41,42). Cell wall acidification resulting from pump stimulation may be at least partly involved in elongation growth, although evidence is accumulating against the acid-growth theory (9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22).…”

Auxin Reduces the Synthesis of Major Vacuolar Proteins in Tobacco Mesophyl Protoplast

“…This type of auxin effect has been reported for different plant species, including monocots (30) and dicots (2,15,17,22,25,(27)(28)(29), and for tissues showing different major physiological responses including cell enlargement (2,27,30) or induction of mitosis (4,16,17). These results have led to the search for (a) the mechanism by which auxin increases or reduces the concentration of particular mRNAs, and (b) the nature of the proteins encoded by these mRNAs in order to determine their role in the physiological response.…”

Insensitivity of the Diageotropica Tomato Mutant to Auxin

“…It is important to distinguish between these two possibilities. If only the induction ofACC synthase is abnormal, the mutant may be useful in identifying the mechanism of selective gene expression regulated by auxin (4,22). On the other hand, if dgt tissues exhibit a general insensitivity to auxin, the mutant may represent a potentially powerful tool for identification and characterization ofthe receptors presumably responsible for auxin action (9,16,18).…”