Some Physiological Characteristics of the Ethylene-requiring Tomato Mutant Diageotropica

Abstract

The diageotropica mutant of tomato (Lycopersicon esculentum Mill.) Ethylene Treatments. Fixed concentrations of ethylene were supplied to whole plants by means of a gas flow system similar to the one described by Goeschl (2). With this system, it was possible to provide accurate continuous flow ethylene atmospheres down to 0.005 ,ul/l depending upon the ethylene concentration in the air.Whole plants were placed in 30-liter containers with an ethylene-air flow rate of 7.5 liters/hr through the container.Concentrations of 10, 1, 0.1, 0.05, 0.005 and 0.0 ,l/ 1 ethylene were applied to plants over a 12-hr period. Lower concentrations could not be accurately measured with available equipment. Treatments, at each concentration, except 10 and 1 tul/l, were repeated three times with two mutant plants at each concentration. Fresh, untreated plants were used in each replicate. No light was provided during treatment. For controls, untreated mutant and normal plants were placed in sealed containers and left on the bench top with the treated material during the 12-hr experiment.Chemical Treatment of Stem Sections and Leaf Segments. Whole plants were brought into the laboratory from the greenhouse. Leaves were immediately cut off the main stem and side branches at the base of the petiole, and leaf segments in turn were cut off the petiole. These were weighed and 1 to 2 g of the leaf material placed in a 50-ml Erlenmeyer flask. The remaining stem internode regions were cut into pieces 20 to 30 mm long, weighed, and placed in 50-ml Erlenmeyer flasks at 10 g/flask.In an initial experiment, 13-ml vials were used with 0.5 to 1 g of stem or leaf tissue in each. One milliliter of water was added to each vial, and one-fifth of the vials were immediately sealed with serum caps. These first vials were sampled for ethylene content after 2 hr, air was blown into each vial to flush out ethylene, and they were then recapped along with 385 www.plantphysiol.org on May 10, 2018 -Published by Downloaded from

Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins

“…Interestingly, similar to plant FKBPs, plant cyclophlins have been strongly linked to regulation of development (Box 2). Mutations in tomato DGT result in auxin-related phenotypes such as lack of lateral roots, deregulation of gene expression, ROS imbalance, and defects in polar auxin transport [80][81][82][83][84][85][86][87][88] (Table 1). DGT is both nuclear and cytoplasmic localized [10] (Table 1, Fig.…”

Insensitivity of the Diageotropica Tomato Mutant to Auxin

“…Application of exogenous ethylene could phenotypically normalize the geotropic response and some morphological features of dge plants (5,27,28), and IAA was less effective in stimulating ethylene synthesis in dgt stem sections as compared to VFN8 (27). These observations led Zobel (27) to propose that dgt is an ethylenerequiring mutant because the failure of auxin to induce ethylene synthesis results in low endogenous levels of ethylene. In subsequent studies, however, endogenous (uninduced) ethylene synthesis rates were not always lower in dgt tissues than in normal 2Abbreviations: dgt, diageotropica; ACC, 1 -aminocyclopropane-1-carboxylic acid; AVG, aminoethoxyvinylglycine; pCPA, para-chlorophenoxyacetic acid; oCPA, ortho-chlorophenoxyacetic acid; FC, fusicoccin; aNAA, a-naphthaleneacetic acid; ,BNAA, #B-naphthaleneacetic acid; NPA, naphthylphthalamic acid; 2,4,5-T, 2,4,5-trichlorophenoxyacetic acid; TIBA, 2,3,5-triiodobenzoic acid.…”

“…The genetic lesion is a mutation in a single gene of the parent variety, VFN8 (26). Application of exogenous ethylene could phenotypically normalize the geotropic response and some morphological features of dge plants (5,27,28), and IAA was less effective in stimulating ethylene synthesis in dgt stem sections as compared to VFN8 (27). These observations led Zobel (27) to propose that dgt is an ethylenerequiring mutant because the failure of auxin to induce ethylene synthesis results in low endogenous levels of ethylene.…”

“…Thus, the fundamental genetic lesion of dgt does not simply result in an inability to synthesize ethylene. Rather, the common feature of the studies cited is the very poor effectiveness of IAA in stimulating ethylene synthesis rates in dgt stems (27), roots (5), and petioles (3) compared to tissue from VFN8.…”

“…The diageotropica tomato mutant is characterized by horizontal shoot and root growth, thin stems, hyponastic leaves, and lack of lateral roots (27,28). The genetic lesion is a mutation in a single gene of the parent variety, VFN8 (26).…”