Auxin Type Research Articles

Effects of exogenous auxin on stem cutting growth of tea (Camellia sinensis)

Root growth rate of a stem cutting was affected by the auxin levels absorbed by the stem cutting. Level of endogenous auxin was insufficient to stimulate the root growth, so that exogenous auxin should be applied. As synthetic auxin was highly expensive, natural auxin sources gained more attention recently to be used. This study was aimed to determine the best source of exogenous auxin triggering the stem cutting growth of tea (Camellia sinensis). This research was conducted using a completely randomized design with four replicates of each treatment. Source of exogenous auxin used in this study consisted of both synthetic (IBA and Rootone-F™) and natural (goat urine and shallot tuber extract) types. These exogenous auxins were applied into the tea stem cutting before planting through dipping method. Growth parameters related to root, shoot and leaf development were observed. Data were evaluated statistically using one-way anova. Application of 6.000 ppm IBA enhanced the rooting percentage and leaf area. Increase of root length was found in the stem cutting treated with 10% goat urine. These results suggested that each type of exogenous auxin stimulated the root growth in a different way. Therefore, proportional combination of these auxin sources might provide a greater support on root growth of tea stem cutting.

Induksi Kalus secara In Vitro dari Daun Cengkeh (Syizigium aromaticum L.) dalam Media dengan Berbagai Konsentrasi Auksin

Clove is an important commodity in Indonesia and it is used as a main material for cigarettes. Clove propagation can be conducted by generative method, but this method takes a long time to produce a considerable number of seedlings. To overcome such problem, it can be applied a tissue culture technique. An effort has been conducted to induce calli from sliced clove leaves and performed at Plant Biotechnology Laboratory, Faculty of Agriculture, Tadulako University from June-November 2016. The aim of this experiment was to determine the most suitable type and concentration of auxins for callus induction of sliced clove leaves via in vitro culture. This experiment used a Completely Randomized Design with six treatments, namely 0.25 ppm 2.4-D; 0.50 ppm 2.4-D; 0.75 ppm 2.4-D; 0.25 ppm NAA; 0.50 ppm NAA; and 0.75 ppm NAA. Parameters observed consisted of the speed or time of appearance, the percentage, color, and texture of calli. Data were analyzed by using analysis of variance and differences between mean treatments were determined by Duncan Multiple Range Test at 5% level. The results of this experiment indicated that the type and concentration of auxin most suitable for callus induction of sliced clove leaves was culture medium supplemented with 0.75 ppm 2.4-D. In such medium composition, it was obtained the quickest callus formation, namely average 4.22 WAC with the percentage of callus formation was up to 100%. In general, the colors of calli were white, yellowish white, and brown; with the textures of formed calli were soft, compact, and intermediat. Keywords: callus formation, clove, growth hormone, tissue culture

Arogenate dehydratases can modulate the levels of phenylacetic acid in Arabidopsis

Phenylacetic acid (PAA) is one type of natural auxin and widely exists in plants. Previous biochemical studies demonstrate that PAA in plants is synthesized from phenylalanine (Phe) via phenylpyruvate (PPA), but the PAA biosynthetic genes and its regulation remain unknown. In this article, we show that the AROGENATE DEHYDRATASE (ADT) family, which catalyzes the conversion of arogenate to Phe, can modulate the levels of PAA in Arabidopsis. We found that overexpression of ADT4 or ADT5 remarkably increased the amounts of PAA. Due to an increase in PAA levels, ADT4ox and ADT5ox plants can partially restore the auxin-deficient phenotypes caused by treatments with an inhibitor of the biosynthesis of indole-3-acetic acid (IAA), a main auxin in plants. In contrast, the levels of PAA were significantly reduced in adt multiple knockout mutants. Moreover, the levels of PPA are substantially increased in ADT4 or ADT5 overexpression plants but reduced in adt multiple knockout mutants, suggesting that PPA is a key intermediate of PAA biosynthesis. These results provide an evidence that members of the ADT family of Arabidopsis can modulate PAA level via the PPA-dependent pathway.

In vitro propagation and medium-term conservation of autochthonous plum cultivar 'Crvena Ranka'

In vitro strategies for the propagation and conservation of indigenous species contribute to the sustainable use of plant diversity and are essential for breeding programs as well. In this study, we established an efficient protocol for the micropropagation of autochthonous plum 'Crvena Ranka' and examined the survival and regrowth capacity of in vitro shoots after 3, 6 and 9 months of cold storage (CS) at +5 oC in total darkness. Aseptic culture was established on the Murashige and Skoog medium containing 2 mg l-1 BA, 0.5 mg l-1 IBA and 0.1 mg l-1 GA3 (leaf rosette initiation being 68.8%). During in vitro propagation on the medium of constant hormonal composition, a significant increase in the multiplication index was observed in the third subculture, whereupon it was mainly stable until the fifth subculture. The effect of BA concentration and/or type of auxins (IBA or NAA) on multiplication parameters, as well as on fresh and dry weights of shoots was evaluated. BA at 1 mg l-1 in combination with NAA significantly increased shoot multiplication parameters. The effect of auxins on rooting parameters was monitored as well. Shoots cultured on the medium supplemented with NAA also displayed higher rooting ability (60%), in comparison with those grown on the medium containing IBA at the same concentration (20%). In vitro shoots can be conserved over the medium term under CS conditions up to six months. High survival was achieved after three (94%) and six months (82.5%), while severe signs of necrosis (100%) were noticed after nine months of conservation. Shoots subcultured under standard growth conditions after CS promptly regained their morphology although their capacity for multiplication and rooting was slightly lower than that of non-cold-stored shoots.

Plant regeneration system in recalcitrant rye (Secale cereale L.)

An effective recovery of plants, genetic engineering, somaclonal variation and haploid induction to improve traits of important crops strongly depend on in vitro systems. For plant molecular breeding and gene transformation, tissue culture is powerful tool. Low efficiency of callus initiation, somatic embryo maturation, and plant regeneration is a major problem in rye tissue culture; therefore, rye is recognized as one of the most recalcitrant species for this process. The aim of this study was to develop optimum, stable and reproducible callus formation and regeneration system for rye to overcome this restriction. To establish an efficient protocol, the effects of three types of explants (intact mature embryo, scratched mature embryo and endosperm-supported mature embryo), carbohydrate source (20 g/L of sucrose and 40 g/L of maltose), auxin type [2,4-dichlorophenoxyacetic acid (2, 4-D), 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 4-Amino-3,5,6-trichloro-2-pyridinecarboxylic acid (picloram)], and auxin concentration (2, 4, 6, 8, 10 and 12 mg/L) on callus formation rate (%), embryogenic callus formation rate (%), responded embryogenic callus rate (%), and regeneration efficiency of rye (Secale cereale L.) were evaluated. The best explant type for plant regeneration was found to be endosperm-supported mature embryo. Our results revealed that the highest responded embryogenic callus rate (60%) and regeneration efficiency (n = 1.24) were obtained from the MS medium containing maltose and 12 mg/L picloram in endosperm-supported mature embryo. This protocol provides a basis for future studies on genetic transformation of rye.

Mass production of coumestrol from soybean (Glycine max) adventitious roots through bioreactor: effect on collagen production

Coumestrol (CMS), one of the soybean isoflavonoids which contains several benefits for maintaining skin function including antiageing properties. In this study, we evaluated various explant sources and plant genotypes to determine competent soybean adventitious root materials for the mass production of CMS, and investigated their skin care efficacies to be used as a novel cosmetic ingredient. Adventitious roots were directly induced from in vitro seedling derived from the mature seeds, extracts were prepared and refluxed for enzymatic deglycosylation. In vitro cell cytotoxicity was evaluated using normal human dermal fibroblast and murine B16 melanoma cells after treatment with increasing concentrations of methanol soybean adventitious roots extracts for 72 h. Finally, in vitro cell assays on HDF cells were performed to evaluate the effect of the soybean adventitious roots extracts in collagen production. The root induction frequency and biomass productivity were significantly affected by plant genotypes, explant sources, the type of auxin used and its concentration. The total CMS production (per 1 L medium) after 4 weeks of culture in a bulb-type bubble bioreactor (3 L capacity) was the highest in the adventitious roots induced from the radicles of Glycine max, ‘Sinhwakong’. Different strengths of Murashige and Skoog (MS) medium were tested to develop culture protocols and the highest total CMS production (per 1 L medium) was observed at 1/2 MS. The content of coumestrin, the glycoside form of CMS, was higher than that of CMS in the roots cultured in 1/2 MS medium for 4 weeks in a bioreactor. The final content of CMS in the ethanol extract after enzymatic deglycosylation was 81.3-fold higher than non-enzymatic deglycosylation. Almost all the coumestrin in the roots were converted to CMS. Further, the enriched CMS root did not exhibit any cell cytotoxicity in normal human dermal fibroblast (HDF) and murine B16 melanoma cells (B16) for 72 h. In addition, in vitro collagen production assay on HDF cells showed that the enriched CMS root increased the collagen production compared to the coumestrol, daidzein, and non-enzyme-treated sample. Thus, enriched CMS root could be potential ingredient for the cosmetic applications

Effect of growth regulators on in vitro micropropagation of blue honeysuckle (Lonicera caerulea L.)

The experiment was carried out in the Tissue Culture Laboratory of the College of Agriculture, University of Karbala to investigate the effect of growth regulators in micropropagation of the blue honeysuckle in vitro. The branches were cultivated by shoot tips in MS medium with five concentrations of each BA and Kin @ 0, 1.0, 1.5, 2.0 and 2.5 mg/l and each concentration was mixed with IAA @ 0.2 mg/l at multiplication stage. At rooting stage, independent experiments were conducted using four concentrations of each IBA and NAA @ 0, 0.5, 1.0 and 1.5 mg/l and each concentration was mixed with steady concentration of 0.2 mg/l of BA. The results indicated that marked differences were observed in plant growth characters under different concentrations of cytokines used. The cytokine concentration of 2.5 mg/l produced significantly higher number of branches, length of branch, and wet and dry weight of vegetative parts compared to control. As for the effect of cytokines type, the BA showed its ’superiority over other cytokines in terms of production of higher number of branches, length of branch, and wet and dry weight of vegetative parts. It was also observed that the auxin types and their concentrations significantly affected the number and length of roots and their wet and dry weights. The IBA concentration of 1.5 mg/l achieved significantly higher number of branches, length of branch, and wet and dry weight of vegetative parts of blue honeysuckle compared to control where no auxin was applied.

New biological trends on cell and callus growth and azadirachtin production in Azadirachta indica.

Azadirachtin is an important secondary metabolite from Azadirachta indica used as a natural biopesticide. This study is the first comprehensive report concerning the influence of plant growth regulators on callus induction, cell suspension growth, and azadirachtin accumulation and production in cell suspension cultures of A. indica. We investigated the effect of plant growth regulators including different types of auxins and cytokinins and their combinations on callus induction, cell suspension growth, and azadirachtin accumulation and production. The highest percentage of callusing (100%) obtained at different combinations of plant growth regulators on MS medium supplemented with 1mg/L picloram and 2mg/L kinetin and the highest fresh weight of callus (264.50mg) was observed in MS medium containing 1.5mg/L NAA and 3mg/L kinetin. In cell suspension cultures, the maximum cell density, SCV, and PCV were 2.44 × 106cells per mL, 97.95%, and 81.46%, respectively, obtained in the MS medium containing 1.5mg/L 2,4-D and 3mg/L zeatin riboside. The highest average growth rate (0.25days) was on MS medium containing 1.5mg/L NAA and 3mg/L zeatin riboside. The MS medium supplemented with 1mg/L picloram and 2mg/L kinetin produced the highest amount of fresh cell weight (493.02g/L), dry cell weight (77.27g/L), azadirachtin accumulation (3.69mg/gDW), and azadirachtin production (285.64mg/L). The results showed that all measured indices had positive correlation with together except FCW and DCW with azadirachtin accumulation.

Improving Rooting of Neem (Azadarachta indica A:Juss) Plant as Responce to Cutting and Auxin Types

Two experimental pots were carried out during the two successive seasons of 2014 and 2015 at the experimental nursery Department fac. of Agric. Damietta Univ. to study the most suitable cuttings types for propagation of neem plant (soft cutting, semi wood and wood cuttings( investigate the effect of auxins treatment Indolbytric acid (IBA1000 ppm) or Naphthalene acetic acid (NAA1000 ppm) plus the control treatment (distilled water) on root formation of neem cuttings. The highest value of rooting percentage, rooting growth, vegetative growth and reducing sugar with soft cuttings of neem plants treated with IBA at 1000 ppm

Induction of somatic embryos of recalcitrant genotypes of <i>Theobroma cacao L.</i>

Objective: In cocoa tree ( Theobroma cacao L .), some elite genotypes have shown, in standard study conditions, an absence or a very weak response to induction of somatic embryos. This is the case of the original C8 genotype Trinidad. This study aims to improve the production of somatic embryos in this genotype Methodology and results : To do this, staminodes and petals excised from immature buds of genotypes C1, C8 and C14 were used. Genotypes C1 and C14 are embryogenic under standard conditions. These floral explants were cultured on induction media differing by the type and concentration of auxins. Callus induction obtained in the three studied genotypes ranged from 80% to 90% with the petal explants and from 70% to 80% with the staminodes regardless of the type and concentration of auxins. Transfer of callogenic explants to DKW (Driver & Kuniyuki, 1984) medium supplemented with sucrose and glucose allowed the induction of somatic embryos at mean rates varying from 5% to 20% after only 84 days with petal explants and media supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D) and 2, 4, 5-trichlorophenoxyacetic acid (2,4,5-T). No induction of somatic embryos was observed on the control medium with the C1, C8 and C14 genotypes. The C1 genotype induced somatic embryos in the presence of all concentrations of auxins. The highest rate of embryogenic callus and somatic embryo induction was obtained with 18 μM of 2, 4, 5-T in all C1 genotypes (39.29 ± 0.28; 17.98 ± 0.10), C8 (36.29% ± 0.26 and 15.01 ± 0.07) and C14 (33.92% ± 0.26 and 14.50 ± 0.16). The 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T). at 18 μM is the most appropriate auxin to remove recalcitrance in cocoa genotype C8. The use of higher 18 μM concentrations of 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T). and its application to other recalcitrant genotypes could confirm its beneficial effect on the removal of recalcitrance to somatic embryogenesis in cocoa. Conclusion and application of results : 18 μM concentration of 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T) gave the best percentage of embryogenic explants and the highest average number of embryos in the three genotypes tested. Therefore, this protocol using 18 μM of 2, 4, 5-trichlorophenoxyacetic acid (2, 4, 5-T) could be used to overcome recalcitrance to somatic embryogenesis in cocoa. Keywords : recalcitrant, cocoa, auxins, somatic embryogenesis

Exogenous auxin type compounds amend PEG-induced physiological responses of pea plants

Drought is among the abiotic stresses, which considerably decrease the agricultural production worldwide. The effects of exogenous auxin-type compounds 1-[2-chloroethoxycarbonyl-methyl]-4-naphthalenesulfonic acid calcium salt (TA-12) and 1-[2-dimethylaminoethoxicarbonylmethyl]naphthalene chlormethylate (TA-14) on drought stress responses induced by polyethylene glycol-6000 (PEG) in garden pea (Pisum sativum L.) plants were investigated. Preliminary application of TA compounds partially restored the normal growth of PEG-treated plants, led to less accumulation of proline, phenolic compounds and low-molecular thiols and did not provoke malondialdehyde buildup. The pea plants pretreated with auxin-type compounds displayed reduction in hydrogen peroxide content and consequently lower oxidative stress levels. This was confirmed by a decrease of the activity of the antioxidant enzymes superoxide dismutase, catalase, and guaiacol peroxidase. Taken together these results showed that the preliminary application of TA-12 and TA-14 reduced the negative effects of drought stress in pea plants.

Growth of Various Chrysanthemum (Chrysanthemum morifolium R.) Cultivars Cuttings on Different Auxin Type

This study aims to obtain qualified seedlings, and speed up the rooting of some varieties ofchrysanthemum (Chrysanthemum morifolium R.) cuttings use synthetic and naturally plant growthregulator (auxin). Research results are expected to be an alternative method of application effectiveand environmentally friendly plant growth regulator. The research was conducted from March toApril 2013 at the Research Institute of Ornamental Plants (Balai Penelitian Tanaman Hias). Theexperimental design used is completely randomized design (CRD) factorial. The first factor is thetype of auxin which consists of four levels ie control, indole acetic acid (IAA), naphthalene aceticacid (NAA), pregnant cow urine, and not pregnant cow urine. The second factor is the type ofchrysanthemum varieties which consists of four levels ie spray type of Puspita Pelangi, spray typeof Puspita Nusantara, standard type of Sakuntala, and standard type of Pasopati. The resultsshowed that type of chrysanthemum cultivars and type of auxin not affected the percentage of livecuttings, percentage of rooted cuttings and percentage of sprouted cuttings. The cuttings root ofplant that given by pregnant cow urine is better than other treatments. Cuttings root length, andnumber of primary root of Pasopati is better than other cultivars. The interaction influence betweenthe type of auxin and chrysanthemum cultivars found only in the number of secondary roots,diameter of root and length of the shoot cuttings at 12 DAP.Keywords: Chrysanthemum morifolium R., cow urine, NAA, spray type

Effect of growth hormone and growth media on the rooting and shooting of Zanthoxylum armatum stem cuttings

The common method of propagation is through seeds but seed germination in Zanthoxylum armatum is very low due to the presence of hard seed coat, which might be a great hurdle for large scale production of plantlets. So an attempt was made in this study to see the effect of different growth hormones, their concentrations and different rooting media on the rooting and sprouting of Z. armatum. The stem cuttings of Z. armatum were treated with two types of auxins namely Indole-3-Butyric Acid (IBA) and Naphthalene Acetic Acid (NAA) at different concentrations (2000 ppm, 3000 ppm and 5000 ppm), while the untreated cuttings were used as control. The cuttings were planted in three different rooting media: sand, neopeat and mix (containing a mixture of sand, soil and vermin-compost). The completely randomized design was used for the experiment. The total number of stem cuttings of Z. armatum used in the experiment was 1080 for 18 treatments in three replicates (20 cuttings per treatment x 18 treatments x 3 replicates). The experiment was set up in controlled greenhouse conditions at Dabur Nepal Private Limited Nursery, Banepa, Kavre District. The parameters evaluated were root length, shoot length and number of roots per cutting. The collected data were analyzed statistically using R-program with Agricola. Least significant difference (LSD) and Duncan multiple Range Test (DMRT), as mean separation technique was applied to identify the most efficient treatment in the rooting and shooting behavior of Z. armatum (Gomez and Gomez, 1984). Hormone concentration and growth media significantly affected the rooting and shooting ability of Z. armatum stem cuttings. IBA was found to be more effective than NAA. Neopeat medium was better than sand and mix media. The highest number of roots (6.5) and root length (11.6 cm) were recorded under IBA 5000 ppm in neopeat medium.

The effects of different concentration of sucrose and various auxin on in vitro shoot and microtuber formation of red potato (Solanum tuberosum, L. var Desiree)

The experiment was aims to study the effect of different sucrose concentrations (30, 90, 120 and 150 g.L−1) and various types of auxin (IAA, IBA, NAA) on in vitro shoot and microtuber formation of Red Potato (Solanum tuberosum, L. var Desiree). Young stem cutting from planlet cultured on half strength MS medium. All types of auxin use the concentration of 0.25 mg.L−1. The research conducted a completely randomized design (CRD) factorial. The data obtained were analyzed by analysis of variance (ANOVA) and DMRT test at 0.05. Parameters observed included growth of microtuber and shoot growth, such as number of shoots and shoot length. The observations result for 3 months, show that the higher the concentration of sucrose, can stimulate tuber formation but suppress shoot growth. Early tuber initiation (36,7 DAP) and optimum number of tuber was observed in 150 g.L−1 sucrose, whereas at 30g.L−1 had no effect to tuber induction. In addition, high number of microtuber was observed in NAA compare to other auxin. Observational data on shoot growth showed that the higher concentration of sucrose will inhibit bud formation. The 90 g.L−1 sucrose concentration showed the best number of shoots, which averaged 1.5 shoots/plantlet. But at a concentration of 30g/L sucrose, explants are only able to form callus. In the bud length parameter, IAA gave the best response that is an average of 3cm/shoot.

An improved micropropagation and ex vitro rooting of a commercially important crop Henna (Lawsonia inermis L.).

An improved micropropagation protocol has been developed for a cosmetically important, dye yielding crop, henna (Lawsonia inermis). Quality of henna product is governed by naphthoquinone based pigment lawsone, thus in vitro multiplication of superior healthy plant to achieve enhanced productivity in terms of dye content and biomass deserve due attention. In the present study, nodal explants collected from an elite plant screened on the basis of superiority in lawsone content was cultured on MS medium supplemented with 0.5μM benzyl adenine (BA) gave significantly (p < 0.05) high number of shoots (24.33). The explants placed on MS medium augmented with 0.5μM BA and 2-isopentenyladenine (2-iP) resulted in the formation of maximum number of shoots (43.67) and was elongated (12.57cm) within 4weeks of culture period. Enhanced axillary bud proliferation and production of mass number of micro shoots was achieved by the continuous subculture in MS medium containing 0.5μM BA and 2-iP. In vitro raised micro shoots were dipped in 0.44mM NAA for 5min followed by planting in polyethylene pots containing a soil: vermiculite (1:1 v/v) mixture produced rooted plantlets (100%). Different auxin types and its concentrations had significant role rooting of L. inermis. Rooting response of various size shoots of L. inermis treated with 0.44mM NAA showed 100% rooting in 4.1-5cm size class shoots. After two months of potting, survived (95%) plants were successfully transferred to medicinal plant garden of the Department. The lawsone content of one-year-old micropropagated plants (23.04mg/gdw) growing in normal environmental conditions and elite mother plant (22.84mg/gdw) was almost similar. Through the present study, efficient cloning of superior germplasm of L. inermis was established.

The plant-growth-promoting actinobacteria of the genus Nocardia induces root nodule formation in Casuarina glauca.

Actinorhizal plants form a symbiotic association with the nitrogen-fixing actinobacteria Frankia. These plants have important economic and ecological benefits including land reclamation, soil stabilization, and reforestation. Recently, many non-Frankia actinobacteria have been isolated from actinorhizal root nodules suggesting that they might contribute to nodulation. Two Nocardia strains, BMG51109 and BMG111209, were isolated from Casuarina glauca nodules, and they induced root nodule-like structures in original host plant promoting seedling growth. The formed root nodule-like structures lacked a nodular root at the apex, were not capable of reducing nitrogen and had their cortical cells occupied with rod-shaped Nocardiae cells. Both Nocardia strains induced root hair deformation on the host plant. BMG111209 strain induced the expression of the ProCgNin:Gus gene, a plant gene involved in the early steps of the infection process and nodulation development. Nocardia strain BMG51109 produced three types of auxins (Indole-3-acetic acid [IAA], Indole-3-Byturic Acid [IBA] and Phenyl Acetic Acid [PAA]), while Nocardia BMG111209 only produced IAA. Analysis of the Nocardia genomes identified several important predicted biosynthetic gene clusters for plant phytohormones, secondary metabolites, and novel natural products. Co-infection studies showed that Nocardia strain BMG51109 plays a role as a "helper bacteria" promoting an earlier onset of nodulation. This study raises many questions on the ecological significance and functionality of Nocardia bacteria in actinorhizal symbioses.

Comparative adventitious root development in pre-etiolated and flooded Arabidopsis hypocotyls exposed to different auxins

Adventitious roots (ARs) emerge from stems, leaves or hypocotyls, being strategic for clonal propagation. ARs may develop spontaneously, upon environmental stress or hormonal treatment. Auxins strongly influence AR development (ARD), depending on concentration and kind. However, the role of different types of auxin is rarely compared at the molecular level. Rooting triggered by light exposure and flooding was examined in intact etiolated Arabidopsis thaliana hypocotyls treated with distinct auxin types. Morphological aspects, rooting-related gene expression profiles, and IAA immunolocalization were recorded. NAA and 2,4-D effects were highly dose-dependent; at higher concentrations NAA inhibited root growth and 2,4-D promoted callus formation. NAA yielded the highest number of roots, but inhibited elongation. IAA increased the number of roots with less interference in elongation, yielding the best overall rooting response. IAA was localized close to the tissues of root origin. Auxin stimulated ARD was marked by increased expression of PIN1 and GH3.3. NAA treatment induced expression of CYCB1, GH3.6 and ARF8. These NAA-specific responses may be associated with the development of numerous shorter roots. In contrast, expression of the auxin action inhibitor IAA28 was induced by IAA. Increased PIN1 expression indicated the relevance of auxin efflux transport for focusing in target cells, whereas GH3.3 suggested tight control of auxin homeostasis. IAA28 increased expression during IAA-induced ARD differs from what was previously reported for lateral root development, pointing to yet another possible difference in the molecular programs of these two developmental processes.

Somatic embryogenesis in Carica papaya as affected by auxins and explants, and morphoanatomical-related aspects.

The aim of this study was to evaluate somatic embryogenesis in juvenile explants of the THB papaya cultivar. Apical shoots and cotyledonary leaves were inoculated in an induction medium composed of different concentrations of 2,4-D (6, 9, 12, 15 and 18 µM) or 4-CPA (19, 22, 25, 28 and 31 µM). The embryogenic calluses were transferred to a maturation medium for 30 days. Histological analysis were done during the induction and scanning electron microscopy after maturing. For both types of auxin, embryogenesis was achieved at higher frequencies with cotyledonary leaves incubated in induction medium than with apical shoots; except for callogenesis. The early-stage embryos (e.g., globular or heart-shape) predominated. Among the auxins, best results were observed in cotyledonary leaves induced with 4-CPA (25 µM). Histological analyses of the cotyledonary leaf-derived calluses confirmed that the somatic embryos (SEs) formed from parenchyma cells, predominantly differentiated via indirect and multicellular origin and infrequently via synchronized embryogenesis. The secondary embryogenesis was observed during induction and maturation phases in papaya THB cultivar. The combination of ABA (0.5 µM) and AC (15 g L-1) in maturation medium resulted in the highest somatic embryogenesis induction frequency (70 SEs callus-1) and the lowest percentage of early germination (4%).

Investigation on rooting ability of twenty olive cultivars from Southern Italy

The effects of two different types of auxins (660 ppm alpha-naph-thaleneacetic acid - NAA - in liquid solution or 750 ppm alpha-naphthaleneac- etamide - NAD - dispersed in a talcum powder) and cuttings from three differ- ent portions of the shoots (basal, middle and apical) on the rooting ability of twenty autochthonous olive cultivars were investigated in two growing seasons (spring and autumn). The results showed that the autochthonous olive cultivars of the Campania Region are characterized by a wide variability in the potential rhizogenic ability. The two periods of cutting collection (March and September) significantly affected the rooting aptitude of the cultivars, indicating that in some cultivars the cuttings collected in autumn had a higher rooting rate than those collected in spring. The effects of NAA and NAD on rooting strongly depended on interaction with the cultivar, time of collection (autumn or spring) and type of cuttings (basal, medium or apical). Among the twenty cultivars tested, we found only eight cultivars with a satisfactory rooting ability after hor- monal applications (Ortolana, Racioppella, Tenacella, Tonda, Biancolilla, Carpellese, Cornia and Pisciottana). In general, the apical and the median portions of the shoots gave the best rooting results.

The role of Zn2+, dimerization and N-glycosylation in the interaction of Auxin-Binding Protein 1 (ABP1) with different auxins.

Auxin is critical for plant growth and development. The main natural auxin is indole-3-acetic acid (IAA), whereas 1-naphthalene acetic acid (NAA) is a synthetic form. Auxin-Binding Protein 1 (ABP1) specifically binds auxins, presumably playing roles as receptor in nontranscriptional cell responses. ABP1 structure was previously established from maize at 1.9 Å resolution. To gain further insight on ABP1 structural biology, this study was carried out employing molecular dynamics simulations of the complete models of the oligomeric glycosylated proteins from maize and Arabidopsis thaliana with or without auxins. In maize, both Zn2+ coordination and glycosylation promoted conformational stability and most of such stabilization effect was located on the N-terminal region. The α-helix of C-terminal regions in ABP1 of both species unfolded during simulations, assuming a more extended structure in maize. In Arabidopsis, the helix appeared more stable, being preserved in most of the monomeric simulations and unfolding when the protein was in the dimeric form. In Arabidopsis ABP1 bound to IAA or NAA, glycosylation structures arranged around the protein, covering the putative site of entrance or egress of auxin. NAA bound protein folding was more similar to the crystal structure showing higher stability compared to that of IAA bound. The molecular structural differences of ABP1 found between the species and auxin types indicate that this auxin-binding protein shows functional specificities in dicots and monocots, as well as in auxin type binding.