Interacción de Giberelinas y Auxinas en la fructificación del tomate

El efecto de la aplicación de giberelinas (GAs) y auxinas durante la fructificación y desarrollo del fruto, ha sido investigado en tomate (Solanum lycopersicum L.) cv Micro-Tom. Los resultados indican que constituye un sistema adecuado para el estudio de la regulación hormonal en tomate. Para evitar la competencia entre frutos dentro del mismo racimo, solo un fruto por racimo y hasta dos racimos por planta se utilizaron en los experimentos. Ovarios no polinizados (emasculados) se desarrollaron partenocárpicamente en respuesta a la aplicación de GA3 > GA1 = GA4 > GA20, aunque no de GA19, y de diferentes auxinas tales como los ácidos indolacético (IAA), naftalenacético (NAA) y 2,4-diclorofenoxiacético (2,4-D), siendo este último el más eficiente. La morfología de los frutos inducidos por auxinas y giberelinas es diferente. En los frutos tratados con GA3 el tejido locular se desarrolla pobremente dejando las cavidades loculares vacías, mientras que los frutos tratados con 2,4-D presentan pseudoembriones y cavidades loculares llenas. A nivel interno, el GA3 indujo células de mayor tamaño en el mesocarpo interno, lo cual estaba correlacionado con un mayor nivel de ploidía (mayor MCV, mean C value), mientras el 2,4-D favoreció las divisiones celulares, por lo que el número de capas celulares en el pericarpo fue superior al tratamiento con GA3 y al polinizado. Los frutos polinizados tuvieron un mayor tamaño y peso que los frutos inducidos con GA3 aunque ambos fueron más pequeños y de menor peso que los tratados con 2,4-D. El grosor del pericarpo de los frutos inducidos con GA3 y 2,4-D no mostró diferencias hasta 20 días después de antesis, por lo que el tener menos células en el pericarpo (frutos inducidos con GA3) podría ser compensado teniendo un mayor tamaño celular. El uso de inhibidores de biosíntesis de GAs tales como el pablobutrazol (PCB) y LAB 198999 disminuyó la fructificación y desarrollo del fruto, efecto revertido con la aplicación de GA3. Sin embargo, en frutSerrani Yarce, JC. (2008). Interacción de Giberelinas y Auxinas en la fructificación del tomate [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/2242Palanci

Targeting hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase for lignin modification in Brachypodium distachyon

This article conducts a study to evaluate the utility of Hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase (HCT) as a target for lignin modification in a species with an “incomplete” shikimate shunt. Results imply that this gene is a preferred target for biotechnological improvement of grasses for bioprocessing

Effect of Gibberellin and Auxin on Parthenocarpic Fruit Growth Induction

The effect of applied gibberellin (GA) and auxin on fruit-set and growth has been investigated in 3 tomato (Solanum lycopersicum L.) cv Micro-Tom. It was found that to prevent competition 4 between developing fruits only one fruit per truss should be left in the plant. Unpollinated 5 ovaries responded to GA3 and to different auxins [indol-3-acetic acid, naphthaleneacetic acid, 6 and 2,4-dichlorophenoxyacetic acid (2,4-D)], 2,4-D being the most efficient. GA3- and 2,4-D7 induced fruits had different internal morphology, with poor locular tissue development in the 8 case of GA, and pseudoembryos development in the case of 2,4-D. Also, GA3 produced larger 9 cells in the internal region of the mesocarp (IM) associated with higher mean C values while 10 2,4-D produced more cell layers in the pericarp than pollinated fruits. The smaller size of GA3- 11 compared to 2,4-D-induced fruits was due to them having fewer cells, only partially 12 compensated by the larger size of IM cells. Simultaneous application of GA3 and 2,4-D 13 produced parthenocarpic fruits similar to pollinated fruits, but for the absence of seeds, 14 suggesting that both kinds of hormones are involved in the induction of fruit development upon 15 pollination. It is concluded that Micro-Tom constitutes a convenient model system, compared to 16 tall cultivars, to investigate the hormonal regulation of fruit development in tomato. 17 Key words: Auxin; Fruit-growth; Fruit-set; Gibberellins; Micro-Tom; Parthenocarpic growth;TomatoMinisterio de Educación y Ciencia, Spain (grant project BIO2003-00151).Peer reviewe

Gibberellin Regulation of Fruit Set and Growth in Tomato1[W]

The role of gibberellins (GAs) in tomato (Solanum lycopersicum) fruit development was investigated. Two different inhibitors of GA biosynthesis (LAB 198999 and paclobutrazol) decreased fruit growth and fruit set, an effect reversed by GA3 application. LAB 198999 reduced GA1 and GA8 content, but increased that of their precursors GA53, GA44, GA19, and GA20 in pollinated fruits. This supports the hypothesis that GA1 is the active GA for tomato fruit growth. Unpollinated ovaries developed parthenocarpically in response to GA3 > GA1 = GA4 > GA20, but not to GA19, suggesting that GA 20-oxidase activity was limiting in unpollinated ovaries. This was confirmed by analyzing the effect of pollination on transcript levels of SlCPS, SlGA20ox1, -2, and -3, and SlGA3ox1 and -2, encoding enzymes of GA biosynthesis. Pollination increased transcript content of SlGA20ox1, -2, and -3, and SlCPS, but not of SlGA3ox1 and -2. To investigate whether pollination also altered GA inactivation, full-length cDNA clones of genes encoding enzymes catalyzing GA 2-oxidases (SlGA2ox1, -2, -3, -4, and -5) were isolated and characterized. Transcript levels of these genes did not decrease early after pollination (5-d-old fruits), but transcript content reduction of all of them, mainly of SlGA2ox2, was found later (from 10 d after anthesis). We conclude that pollination mediates fruit set by activating GA biosynthesis mainly through up-regulation of GA20ox. Finally, the phylogenetic reconstruction of the GA2ox family clearly showed the existence of three gene subfamilies, and the phylogenetic position of SlGA2ox1, -2, -3, -4, and -5 was established

Inhibition of Auxin Transport from the Ovary or from the Apical Shoot Induces Parthenocarpic Fruit-Set in Tomato Mediated by Gibberellins

Fruit-set in tomato (Solanum lycopersicum L.) depends on gibberellins and auxin (GAs). Here we show, using the cv MicroTom, that application of N-1- naphthylphthalamic acid (NPA) (an inhibitor of auxin transport) to unpollinated ovaries induced parthenocarpic fruit-set, associated with an increase of indole-3-acetic acid (IAA) content, and that this effect was negated by paclobutrazol (PAC; an inhibitor of GA biosynthesis). NPA-induced ovaries contained higher content of GA1 (an active GA) and transcripts of GA biosynthetic genes (SlCPS, SlGA20ox1 and -2). Interestingly, application of NPA to pollinated ovaries prevented their growth, potentially due to supraoptimal IAA accumulation. Plant decapitation, and inhibition of auxin transport by NPA from the apical shoot, also induced parthenocarpic fruit growth of unpollinated ovaries. Application of IAA to the severed stump negated the plant decapitation effect, indicating that the apical shoot prevents unpollinated ovary growth through IAA transport. Parthenocarpic fruit growth induced by plant decapitation was associated with high levels of GA1 and was counteracted by PAC treatment. Plant decapitation also produced changes in transcript levels of genes encoding enzymes of GA biosynthesis (SlCPS and SlGA20ox1) in the ovary, quite similar to those found in NPA-induced fruits. All these results suggest that auxin can have opposing effects on fruit-set, either inducing (when accumulated in the ovary) or repressing (when transported from the apical shoot) that process, and that GAs act as mediators in both cases. The effect of NPA application and decapitation on fruit-set induction was also observed in MicroTom lines bearing introgressed D (DWARF) and Sp (SELT23 PRUNING) wild type alleles.Ministerio de Educación y Ciencia of 19 Spain (BIO2006-13437).Peer reviewe

4-Coumarate 3-hydroxylase in the lignin biosynthesis pathway is a cytosolic ascorbate peroxidase

Lignin biosynthesis in higher plants relies upon a 3-hydroxylation reaction that can occur via shikimate esters of 4-coumarate. Here, Barros et al. define an alternative biosynthetic pathway via cytosolic ascorbate peroxidase that can catalyze direct 3-hydroxylation of 4-coumarate