Phytotropins

Abstract

Certain members of the phytotropin class of auxin transport inhibitors are shown to bind with high affinity to the known naphthylphtlamlc aid binding sites in maize (Zea mays) coleoptiles. The binding site Is, thus, a phytotropin binding site. In general, the degree of binding correlates with the phytotropin structure activity rules and with physiological activities of model compounds. It is argued that the binding site may be a receptor, and it also may be the receptor involved in the control of the auxin transport process. The possibility is raised that the binding sites may be intrinsic receptors for endoanalog(s) of the phytotropins.

Maize LAZY1 Mediates Shoot Gravitropism and Inflorescence Development through Regulating Auxin Transport, Auxin Signaling, and Light Response

“…7, A and B). Furthermore, treatment with 5 mM NPA (Katekar et al, 1981;Bailly et al, 2008;Peer et al, 2009) inhibited the acceleration of la1-ref mesocotyls in the dark, implying that the longer mesocotyls and shorter coleoptiles in la1-ref mutants are primarily due to increased basipetal PAT (Fig. 7, A and B).…”

Disruption of the Polar Auxin Transport System in Cotton Seedlings following Treatment with the Defoliant Thidiazuron

“…These compounds exhibit activity both when sprayed on plants and when incorporated directly into agar receiver blocks (7,19). Where examined, all of these inhibitors effectively modify binding of 3H-NPA to microsomal membrane preparations (8,15,19). Incorporation of TDZ into the receiver blocks has no effect on IAA transport (Table II).…”

PIS1, a negative regulator of the action of auxin transport inhibitors in Arabidopsis thaliana

“…However, it is rather surprising that NPA and TIBA acted similarly in the sensitivity alteration of the pis1 to different classes. Although these various classes of inhibitors essentially exhibit similar effects, they also (as mutant, since, in addition to the structural difference, NPA and TIBA have been considered to have different binding described above) display a number of differences with regard to both physiological effects and competitive bindsites (Brunn et al, 1992;Depta et al, 1983;Sussman and Goldsmith, 1981;Thomson et al, 1973). An interpretation ing assays.…”

“…Although the effects of these classes of inhibitors including growth of seedlings, root elongation, root gravitropism, root phototropism and root curling. The mutant fundamentally overlap with each other, a number of differences are observed both in physiological effects (Gaither also exhibits hypersensitivity to TIBA but the responses to HFCA are unaffected, indicating that the PIS1 gene product and Abeles, 1975;Katekar and Geissler, 1980;Schneider, 1970) and in competitive binding assays (Brunn et al, 1992; might be specifically involved in the response pathway of NPA/TIBA and might act as a negative regulator of the Depta et al, 1983;Sussman and Goldsmith, 1981;Thomson et al, 1973).…”