Involvement of ethylene in the rooting of seedling shoot cultures of Bixa orellana L.

Abstract

Using seedlings derived from the shoot apex of annatto (Bixa orellana L. cv. Bico-de-Pato) we observed the rooting frequency of B. orellana, the number and length of roots and the rate of ethylene production during 30 d in culture. The rhizogenesis response was affected by auxins (NAA or IBA) and by both the ethylene biosynthesis precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and the inhibitor 2-aminoethoxyvinylglycine (AVG). Auxin supplementation to the medium resulted in root induction, ethylene production, and an undesirable callusing in the epidermal and cortical tissues. Irrespective of the presence of auxins, supplementing the medium with ACC promoted ethylene biosynthesis and callusing, which resulted in increased cell proliferation mainly in the cortical and vascular tissues, while the epidermis was mostly unaltered. In both ACC and auxin-supplemented medium, increased ethylene production and callusing occurred, suggesting a synergistic effect between these two responses. ACC was capable of inducing adventitious root formation, but the roots produced had a wrinkled appearance when compared to normal roots. Conversely, AVG reduced ethylene production and callusing, while the epidermis, cortex, and inner tissues remained unaltered, regardless of the presence of auxins. AVG was beneficial in these aspects, although its application led to a reduction in the number of roots and in the average root length. In conclusion, it was not possible to establish a direct relation between ethylene and rooting, but we hypothesize that, under the experimental conditions described, ethylene may enhance tissue sensitivity to auxin. However, ethylene did not seem essential to the rhizogenesis process in annatto.

Molecular and physiological characterization of the effects of auxin-enriched rootstock on grafting

“…Auxin also interacts with other hormones during graft union formation 5 . Ethylene is involved in the wounding response and promotes cell expansion 13 , 14 , and the exogenous application of ethylene promotes callus formation to result in increased cell proliferation 15 . The ethylene signaling-defective Arabidopsis mutant ein2 shows incomplete healing during tissue reunion, and incised inflorescence stems of this mutant exhibit inhibited expression of the transcription factor gene ANAC071 , which is needed for the division of pith cells during reunion.…”

“…The expression of ANAC071 is also induced by auxin during this process 11 . Moreover, the application of the ethylene biosynthesis inhibitor AVG (2-aminoethoxyvinylglycine) to auxin (indole-3-butyric acid [IBA] or naphthalene acetic acid [NAA])-supplemented medium inhibits callus formation at the base of the shoot 15 . These findings indicate that ethylene and auxin interact during graft union formation, but further studies are needed to elucidate the detailed mechanism.…”

Ethylene and polyamine interactions in morphogenesis of Passiflora cincinnata: effects of ethylene biosynthesis and action modulators, as well as ethylene scavengers

“…Ethylene greatly influences the regeneration capacity of plant material, either promoting or inhibiting morphogenetic processes in several species, such as Nicotiana tabacum (Biondi et al 1998), Malus domestica (Ma et al 1998), Phaseolus vulgaris (Carvalho et al 2000), Passiflora edulis f. flavicarpa (Reis et al 2003), Carica papaya (Magdalita et al 1997), Bixa orellana (Paiva Neto et al 2009) Actinidia deliciosa (Arigita et al 2003), Arachis hypogaea (Ozudogru et al 2005), Capsicum chinense (Santana-Buzzy et al 2006), and Cydonia oblonga (Marino et al 2008). Results suggest that there is a relationship between sensitivity of seedlings to ethylene and the climacteric characteristics of the fruit (Jona et al 2002).…”