Identification of the metabolites of Indole-3-acetic acid in growing hypocotyls of Lupinus albus

Sánchez-Bravo, José; Ortuño, A.; Botía, J. M.; Rı́o, José Antonio del; Caballero, M. Victoria; Acosta, Manuel; Sabater, F.

doi:10.1007/bf00024917

Cited by 5 publications

(3 citation statements)

References 31 publications

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“…At different times, the length of the zones was measured without removing the plants from the buffer. (21). A HPLC analysis of the acetonitrile extracts (21) showed that 14C activity corresponds mainly to unaltered IAA, whereas 3H activity includes decarboxylation products and a small percentage of IAA (3%) conjugates in addition to LAA.…”

Section: Plant Materials and Measurement Of Growthmentioning

confidence: 99%

“…A HPLC analysis of the acetonitrile extracts (21) showed that 14C activity corresponds mainly to unaltered IAA, whereas 3H activity includes decarboxylation products and a small percentage of IAA (3%) conjugates in addition to LAA. According to this, a decrease of the ratio of 14C to 3H in the acetonitrile extracts compared to the ratio in the applied LAA solution can be considered as an index of IAA decarboxylation (19), as was already demonstrated (21). From the distribution of radioactivity along the hypocotyls, the velocity of IAA transport was calculated either from the displacement of the radioactive pulse or from the position of the radioactive front.…”

Section: Plant Materials and Measurement Of Growthmentioning

confidence: 99%

“…Because previous reports showed that lupin hypocotyls exhibited a high capacity to metabolize exogenously added IAA (19)(20)(21) (19,20) do not interfere with the possible variation of IAA transport down the organ.…”

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The Decrease in Auxin Polar Transport Down the Lupin Hypocotyl Could Produce the Indole-3-Acetic Acid Distribution Responsible for the Elongation Growth Pattern

Sánchez-Bravo¹,

Ortuño²,

Botía³

et al. 1992

Plant Physiol.

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The variation of indole-3-acetic acid (IAA) transport along Lupinus albus L. hypocotyls was studied using decapitated seedlings and excised sections. To confirm that the mobile species was IAA and not IAA metabolites, dual isotope-labeled IAAs, [5-3H]IAA + [1-'4CJIAA, were used. After apical application to decapitated seedlings, the longitudinal distribution of both isotopes at different transport periods showed that the velocity of IAA transport was higher in the apical, elongating region than in the basal, nongrowing region. This variation in velocity was not a traumatic consequence of decapitation because after application of IAA to the basal region of decapitated seedlings, both the velocity and intensity of IAA transport were lower than in the apical treatment. The variation in IAA transport down the hypocotyl was confirmed when it was measured in excised sections located at different positions along the hypocotyl. The velocity and, to a greater extent, the intensity of IAA transport decreased from the apical to the basal sections. Consequently, if the amount of IAA reaching the apical zones of lupin hypocotyl were higher than the IAA transport capacity in the basal zones, accumulation of mobile IAA might be expected in zones located above the basal region. In fact, an IAA accumulation occurred in the elongating region during the first 4-h period of transport after apical treatment with IAA. It is proposed that the fall in IAA transport along the hypocotyl might be responsible for the IAA distribution and, consequently, for the growth distribution reported in this organ. An indirect proof of this was obtained from experiments that showed that the excision of the slowly transporting basal zones strongly reduced the growth in the remaining part of the organ, whereas excision of the root caused no significant modification in growth during a 20-h period.The frequently described correlations between the longitudinal distribution of IAA and growth in stem axes suggest that in some tissues, cell elongation is regulated mainly by the endogenous levels of auxin (15,18,22,26,28,29). In plant systems, such as coleoptiles or hypocotyls, the apex is the main source of auxin. Therefore, it can be suspected that basipetal polar auxin transport might be involved in supplying auxin for growth in these systems. Auxin transport has been intensively investigated for decades, and several hypotheses have been formulated to account for the characteristics of the process (see reviews by Goldsmith [2], Kaldewey [7], Rubery [17]). However, the actual mechanism responsible for IAA distribution, which presumably causes the growth distribution, remains uncertain.Contrary to those reported for sunflower hypocotyls (1), some data suggest that mobile auxin is involved in the regulation of elongation growth in etiolated lupin hypocotyls. Thus, [5-3H]IAA-fed decapitated seedlings showed a wave of unaltered LAA in the elongation zone that correlated with the distribution of growth (12), as well as with the distribution of endogenous ...

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Section: Plant Materials and Measurement Of Growthmentioning

confidence: 99%

Section: Plant Materials and Measurement Of Growthmentioning

confidence: 99%

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The Decrease in Auxin Polar Transport Down the Lupin Hypocotyl Could Produce the Indole-3-Acetic Acid Distribution Responsible for the Elongation Growth Pattern

Sánchez-Bravo¹,

Ortuño²,

Botía³

et al. 1992

Plant Physiol.

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Uptake and decarboxylation of indole-3-acetic acid during auxin-induced growth in lupin hypocotyl segments

Botía

Ortuño

Sabater

et al. 1994

Planta

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The elongation growth of etiolated hypocotyl segments of lupin (Lupinus albus L.) was stimulated by acid pH (4.6 versus 6.5) and by IAA for periods of up to 4 h. After this time, the segments were unable to grow further. In the presence of an optimal IAA concentration (10 gM), acid pH increased the growth rate but had no effect on final growth. With suboptimal IAA (0.1 laM), however, acid pH increased growth in a more than additive way, suggesting a synergistic action between the two factors. This synergism may be explained by the increased IAA uptake and decarboxylation seen at an acid pH. These results reinforce the view that the effects of low pH and IAA on growth are not independent. Vanadate inhibited growth and also IAA uptake and decarboxylation. This inhibitor, therefore, probably inhibits growth not only by decreasing ATPase-mediated acidification but also by decreasing H+-dependent IAA uptake from the apoplasm. This dependence of IAA uptake on ATPase may be mediated by apoplasmic acidification. The amount of IAA decarboxylated increased when the assay conditions favored the growth of segments, indicating that IAA could be destroyed by decarboxylation during the auxin-induced growth.

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

Botía

Ortuño

Acosta

et al. 1992

J Plant Growth Regul

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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.

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Identification of the metabolites of Indole-3-acetic acid in growing hypocotyls of Lupinus albus

Cited by 5 publications

References 31 publications

The Decrease in Auxin Polar Transport Down the Lupin Hypocotyl Could Produce the Indole-3-Acetic Acid Distribution Responsible for the Elongation Growth Pattern

The Decrease in Auxin Polar Transport Down the Lupin Hypocotyl Could Produce the Indole-3-Acetic Acid Distribution Responsible for the Elongation Growth Pattern

Uptake and decarboxylation of indole-3-acetic acid during auxin-induced growth in lupin hypocotyl segments

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

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