Influence of 2,3,5-triiodobenzoic acid on the transport and metabolism of IAA in lupin hypocotyls

Abstract

The influence of 2,3,5-triiodobenzoic acid (TIBA) on the transport and metabolism of indolyl-3-acetic acid (IAA) was studied in etiolated lupin (Lupinus albus L) hypocotyls. Double isotope-labeled IAA [(5-3H)-IAA plus (1-14C)-IAA] was applied to the cut surface of decapitated seedlings. This confirmed that the species mobilized was unaltered IAA and permitted us to measure the in vivo decarboxylation of applied IAA. A pretreatment with TIBA applied to the cut surface produced a partial or drastic inhibition in the basipetal IAA movement at 0.5 or 100 IxM, respectively. Since TIBA inhibits auxin polar transport by interfering with the effiux carrier, the above results suggest that 100 I~M TIBA is sufficient to saturate the binding sites in the transporting cells. Compared to the control plants, in vivo decarboxylation of IAA was enhanced in 0.5 ~M TIBA-treated plants, while no decarboxylation was detected after treatment with 100 I~M TIBA. The in vitro decarboxylation of (1-14C)-IAA catalyzed by purified peroxidase was moderately activated by 100 ~M and unaffected by 0.5 ~xM TIBA. The paradoxical effect of TIBA in vivo vs in vitro assays suggests that the in vivo effect of TIBA on IAA oxidation might be the consequence of the action of TIBA on the auxin transport system. Thus, transport reduction by 0.5 ~M TIBA caused a temporary accumulation of IAA in that apical region of the hypocotyl which has the highest capacity to decarboxylate IAA. In the presence of I00 ~M TIBA, a concentration which presumably saturates the effiux carriers, most of the added IAA can be expected to be located in the transporting cells where, according to the present data, IAA decarboxylation cannot take place.

Influence of 2,3,5-Triiodobenzoic Acid and 1-N-Naphthylphthalamic Acid on Indoleacetic Acid Transport in Carnation Cuttings: Relationship with Rooting

“…Radioactivity in zone 2 also increased after apical application of TIBA (Fig. 4A), which agrees with the idea that TIBA itself may be polarly transported in a basipetal direction, as was demonstrated by Thomson et al (1973) and observed by Botía et al (1992). However, apical application of NPA resulted in higher immobilization in zone 1 and no variation in zone 2 compared to the basipetal control (Fig.…”

Nanometer accuracy statistical interferometric technique in monitoring the short-term effects of exogenous plant hormones, auxin and gibberellic acid, on rice plants

“…The influences of 2,3,5-triiodobenzoic acid (TIBA) on the transport and metabolism of auxin were studied with different plant species (Botía et al 1992;Karabaghli-Degron et al 1998). Plant system under different concentrations of TIBA was investigated (Begum et al 2016;Kučerová et al 2016;Shinkle and Briggs 1984) and found the inhibitory effect of TIBA for auxin signalling.…”

Growing in darkness

“…4,5 Additional (MDR/PGP) 7 or parallel *Correspondence to: José Sánchez Bravo; Departamento de Biología Vegetal (Fisiología Vegetal); Facultad de Biología; Universidad de Murcia; Campus de Espinardo; Murcia 30100 Spain; Email: jsbravo@um.es inhibitors of polar auxin transport (PAT) such as 2,3,5-triiodobenzoic acid and 1-N-naphthylphtalamic acid (NPA). 16,17 Basipetal PAT mainly occurred in the stele, 15 while cells in the epidermis and outer cortex are the limiting factor in auxin-induced shoot growth. [18][19][20] The finding that during PAT auxin can move laterally from transporting cells in the stele to the outer tissues of the elongation zone 15 could explain the apparent conflict between the localization of PAT and the auxin target cells for elongation.…”