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[EN] Gibberellins (GA) and auxin (indole-3-acetic acid, IAA) are considered the main compounds involved in the induction of fruit set. Citrus trees flower profusely but exhibit dramatically low fruit set rates and, in particular, seeded orange cultivars also require pollination for fruit to adequately set. Consequently, they represent an excellent model to investigate the interactions between both hormones and their effect on fruit set and development. Unpollinated ovaries from 'Pineapple' sweet orange trees were treated with IAA and pollinated ones with TIBA (2,3,5-triiodobenzoic acid, inhibitor of auxin transport), and changes in ovaries were registered shortly after the treatments. The highest IAA levels were found in unpollinated ovaries treated with auxin (twofold increase compared to pollinated ones), and the lowest corresponded to pollinated ones supplemented with TIBA (30% reduction). GA content also differed substantially among samples. In general, expression of the GA-biosynthetic gene GA20ox2 in the ovule and pericarp paralleled the changes in GA(20) content in both tissues, and also expression of GA3ox1 and GA(1) content but only in the ovule. The levels of these GA in unpollinated ovaries were promoted in response to exogenous IAA, whereas expression of the GA-inactivation gene GA2ox1 and the concentration of the GA-catabolite GA(8) were reduced by this treatment. Significantly, treatments with GA(3) or IAA to unpollinated ovaries recovered fruit set to the level reached by free pollinated ones. Our study demonstrates that IAA alters GA metabolism in citrus leading to marked changes in the active GA(1) levels in ovules and pericarp, mainly through the regulation of GA-biosynthetic genes and the inhibition of the catabolic pathway.

[EN] Gibberellins (GA) and auxin (indole-3-acetic acid, IAA) are considered the main compounds involved in the induction of fruit set. Citrus trees flower profusely but exhibit dramatically low fruit set rates and, in particular, seeded orange cultivars also require pollination for fruit to adequately set. Consequently, they represent an excellent model to investigate the interactions between both hormones and their effect on fruit set and development. Unpollinated ovaries from 'Pineapple' sweet orange trees were treated with IAA and pollinated ones with TIBA (2,3,5-triiodobenzoic acid, inhibitor of auxin transport), and changes in ovaries were registered shortly after the treatments. The highest IAA levels were found in unpollinated ovaries treated with auxin (twofold increase compared to pollinated ones), and the lowest corresponded to pollinated ones supplemented with TIBA (30% reduction). GA content also differed substantially among samples. In general, expression of the GA-biosynthetic gene GA20ox2 in the ovule and pericarp paralleled the changes in GA(20) content in both tissues, and also expression of GA3ox1 and GA(1) content but only in the ovule. The levels of these GA in unpollinated ovaries were promoted in response to exogenous IAA, whereas expression of the GA-inactivation gene GA2ox1 and the concentration of the GA-catabolite GA(8) were reduced by this treatment. Significantly, treatments with GA(3) or IAA to unpollinated ovaries recovered fruit set to the level reached by free pollinated ones. Our study demonstrates that IAA alters GA metabolism in citrus leading to marked changes in the active GA(1) levels in ovules and pericarp, mainly through the regulation of GA-biosynthetic genes and the inhibition of the catabolic pathway.

[EN] In this work, we study the capacity to biosynthesize gibberellins (GA) of ovules (either fertilised or unfertilised), developing seeds and pericarp from fruitlets and their relation with fruit set capacity. Experiments were performed in adult, 12-year-old trees of seeded (Pineapple) and seedless parthenocarpic (Washington navel) sweet orange [Citrus sinensis L. Osbeck] cultivars. The activity of GA20-, GA3- and GA2-oxidases and gibberellin levels were measured in the ovules and pericarp of fruitlets in different development states. The results indicate that ovules are the main sites of gibberellin synthesis in fruitlets during the post-anthesis period. The most intense GA(1) synthesis-coincident with the highest expression of GA20ox2, GA3ox1 and GA2ox1-was detected in the ovules of the seeded cultivar, probably induced by fecundation and associated with low early fruitlet abscission rates. By contrast, the low activity detected in the sterile cultivar appears to be rather developmentally or constitutively regulated. As a fruitlet develops, the GA(1) concentration is augmented in the pericarp in comparison to ovules or developing seeds, and levels therein did not exhibit noticeable differences between varieties. Furthermore, developing seeds from pineapple had higher GA(1) content than the unfertilised abortive ovules from Washington navel. Taken together, data suggest a main role for this hormone in the control of fruitlet abscission, and also demonstrate a function in seed development.

[EN] In this work, we study the capacity to biosynthesize gibberellins (GA) of ovules (either fertilised or unfertilised), developing seeds and pericarp from fruitlets and their relation with fruit set capacity. Experiments were performed in adult, 12-year-old trees of seeded (Pineapple) and seedless parthenocarpic (Washington navel) sweet orange [Citrus sinensis L. Osbeck] cultivars. The activity of GA20-, GA3- and GA2-oxidases and gibberellin levels were measured in the ovules and pericarp of fruitlets in different development states. The results indicate that ovules are the main sites of gibberellin synthesis in fruitlets during the post-anthesis period. The most intense GA(1) synthesis-coincident with the highest expression of GA20ox2, GA3ox1 and GA2ox1-was detected in the ovules of the seeded cultivar, probably induced by fecundation and associated with low early fruitlet abscission rates. By contrast, the low activity detected in the sterile cultivar appears to be rather developmentally or constitutively regulated. As a fruitlet develops, the GA(1) concentration is augmented in the pericarp in comparison to ovules or developing seeds, and levels therein did not exhibit noticeable differences between varieties. Furthermore, developing seeds from pineapple had higher GA(1) content than the unfertilised abortive ovules from Washington navel. Taken together, data suggest a main role for this hormone in the control of fruitlet abscission, and also demonstrate a function in seed development.

The endogenous levels of 13 gibberellins (GAs), three cytokinins (CKs), abscisic acid (ABA), indole-3-acetic acid (IAA) and jasmonic acid (JA) were analyzed in naturally pollinated ovaries of three mandarin cultivars selected for their different capacity to produce seeds and their differing parthenocarpic ability. The varieties compared were Murcott (pollen self-compatible, highly seeded), Moncada (self-incompatible, moderately seeded), and Moncalina (pollen sterile, seedless), obtained from Moncada by bud gamma-irradiation. As expected, the 13-hydroxylation pathway was predominant in ovaries and our results further indicate that cultivar differences exist in GA metabolism. The active gibberellin GA(1) levels in ovaries seems to be related with presence of fertilized ovules and, therefore, with the ability to produce the seeds of a variety. Sterility gamma irradiation arrested the biosynthesis of GA(1) and its precursor GA(19) in Moncalina ovaries if compared to Moncada. The productive efficiency of the studied cultivars also indicated that fruit set depends strongly on the GA(1) level achieved by ovaries, which is also closely related with carbohydrate content. The study of the expression of gibberellin-oxidase genes showed that the pollination/fecundation process enhances GA20ox2 and GA3ox1 activities in naturally pollinated Murcott and Moncada ovaries compared with unpollinated Murcott and Moncalina, respectively. GA2ox1 expression was lower in the ovaries of the highly seeded cultivar Murcott than in those of Moncada or Moncalina. Unpollinated Murcott ovaries contained much lower levels of GA(1) and IAA than the naturally pollinated ovaries of this cultivar. Conversely, unpollinated ovaries, which exhibited 100 % abscission, had more ABA and JA contents. Cytokinin activity seemed constitutive and independent of pollination/fecundation. However, trans-zeatin (t-Z) and 2-isopentenyl adenine (2-IP) concentrations were higher in Murcott ovaries than in Moncada/Monca

The endogenous levels of 13 gibberellins (GAs), three cytokinins (CKs), abscisic acid (ABA), indole-3-acetic acid (IAA) and jasmonic acid (JA) were analyzed in naturally pollinated ovaries of three mandarin cultivars selected for their different capacity to produce seeds and their differing parthenocarpic ability. The varieties compared were Murcott (pollen self-compatible, highly seeded), Moncada (self-incompatible, moderately seeded), and Moncalina (pollen sterile, seedless), obtained from Moncada by bud gamma-irradiation. As expected, the 13-hydroxylation pathway was predominant in ovaries and our results further indicate that cultivar differences exist in GA metabolism. The active gibberellin GA(1) levels in ovaries seems to be related with presence of fertilized ovules and, therefore, with the ability to produce the seeds of a variety. Sterility gamma irradiation arrested the biosynthesis of GA(1) and its precursor GA(19) in Moncalina ovaries if compared to Moncada. The productive efficiency of the studied cultivars also indicated that fruit set depends strongly on the GA(1) level achieved by ovaries, which is also closely related with carbohydrate content. The study of the expression of gibberellin-oxidase genes showed that the pollination/fecundation process enhances GA20ox2 and GA3ox1 activities in naturally pollinated Murcott and Moncada ovaries compared with unpollinated Murcott and Moncalina, respectively. GA2ox1 expression was lower in the ovaries of the highly seeded cultivar Murcott than in those of Moncada or Moncalina. Unpollinated Murcott ovaries contained much lower levels of GA(1) and IAA than the naturally pollinated ovaries of this cultivar. Conversely, unpollinated ovaries, which exhibited 100 % abscission, had more ABA and JA contents. Cytokinin activity seemed constitutive and independent of pollination/fecundation. However, trans-zeatin (t-Z) and 2-isopentenyl adenine (2-IP) concentrations were higher in Murcott ovaries than in Moncada/Monca

Two series of halogenated 1-benzyl-7-chloro-6-hydroxy-tetrahydroisoquinolines were prepared to explore the influence of each series on the affinity for dopamine receptors. All the compounds displayed a high affinity for D(1)-like and/or D(2)-like dopamine receptors in striatal membranes, although they were unable to inhibit [(3)H]-dopamine uptake in striatal synaptosomes. The halogen placed on the benzylic ring in 1-benzyl-THIQs, compounds of the series 1, 2'-bromobenzyl derivatives with K(i) values into the nanomolar range, and the series 2, 2',4'-dichlorobenzyl-THIQ homologues, proves to be an important factor to modulate affinity at dopamine receptor. (C) 2009 Elsevier Masson SAS. All rights reserved.

Two series of halogenated 1-benzyl-7-chloro-6-hydroxy-tetrahydroisoquinolines were prepared to explore the influence of each series on the affinity for dopamine receptors. All the compounds displayed a high affinity for D(1)-like and/or D(2)-like dopamine receptors in striatal membranes, although they were unable to inhibit [(3)H]-dopamine uptake in striatal synaptosomes. The halogen placed on the benzylic ring in 1-benzyl-THIQs, compounds of the series 1, 2'-bromobenzyl derivatives with K(i) values into the nanomolar range, and the series 2, 2',4'-dichlorobenzyl-THIQ homologues, proves to be an important factor to modulate affinity at dopamine receptor. (C) 2009 Elsevier Masson SAS. All rights reserved.