Brassinosteroid-stimulated branch elongation in the marubakaido apple rootstock

Abstract

Brassinosteroids (BRs) comprise a specific class of low-abundance plant steroids now recognized as a new class of phytohormones. In this paper, we demonstrate that a fluoro derivative of 28-homocastasterone (5F-HCTS) stimulates branch elongation in in vitro-grown shoots of Malus prunifolia, the marubakaido apple rootstock. In addition to that, we show that this BR-stimulated branch elongation is paralleled by an increase in ethylene release. However, either the presence of 1-amino-cyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene in higher plants, in the culture medium or an ethylene-enriched atmosphere resulted in inhibition of branch elongation, indicating that the stimulation of branch elongation observed for 5F-HCTS-treated shoots in this study was not, at least directly, related to the BR-induced enhancement in ethylene release rate. Besides its positive effect on the marubakaido shoot growth, i.e. branch elongation, the 5F-HCTS-driven enhancement of branch elongation found in this study is potentially useful to improve micropropagation techniques for other plant species as well, especially woody species, in which branch elongation is typically a constraint for efficient micropropagation.

In VitroEffects of Brassinosteroids on the Growth and Antioxidant Enzyme Activities in Groundnut

“…In the present studies, BR effectively stimulated the elongation and formation of lateral shoots and shoot buds. Similar results were reported by PereiraNetto et al [25,26] might be due to their genetic make-up. In the presence of BA (3 mg L −1 ), shoot formation was observed at lower concentrations of BR indicating that the interaction of PGRs altered the shooting response.…”

Comparative analysis of the effects of homocastasterone and two derivatives on shoot and main root elongation of tomato plantlets

“…In this study, comparative analysis of the effect of the 5␣-monofluoro derivative of 28-HCS, a compound highly effective towards shooting in the Marubakaido apple rootstock (Schaefer et al, 2002), 5OH-HCS and the parent compound 28-HCS, along with epi-BL on shoot elongation demonstrated that shoots are more responsive to 28-HCS, compared to both of the 28-HCS derivatives used in this trial. When seen together, results from the pioneer work (Ramirez et al, 2000), together with previously reported data from our laboratories for shoots of Eucalyptus (Pereira-Netto et al, 2006a) and the Marubakaido apple rootstock (Pereira-Netto et al, 2003, 2006b treated with fluoro and hydroxy derivatives of 28-HCS, and 28-HCS itself, along with results from this study provide some interesting information concerning biochemical action of these compounds at a molecular level. These findings, clearly show that fluoro and hydroxy substitutions on carbon 5 of 28-HCS, change the ability of the parental 28-HCS to stimulate or inhibit plant's responses, for example root and shoot elongation, depending on the chosen system, i.e.…”

“…The internal components of plant signaling are typically mediated by chemical growth regulators (Azpiroz et al, 1998), and most multicellular organisms rely on steroids as signaling molecules for the regulation of physiological and developmental programs (Wang et al, 2001). We have previously demonstrated that exogenous BRs at doses at the microgram per shoot range are able to significantly change shoot arquitecture, stimulating or inhibiting shoot formation and elongation of in vitro-grown trees such as a hybrid between Eucalyptus grandis and Eucalyptus urophylla (Pereira-Netto et al, 2006a) and the Marubakaido rootstock (Schaefer et al, 2002;Pereira-Netto et al, 2006b), depending on the kind and dose of the BR used and/or the kind of shoot considered. Analysis of the changes on the average shoot and main root length in tomato plantlets (this work) clearly show that 5F-HCS more effectively stimulates main root elongation compared to shoot elongation.…”

Evaluation of biological activity of new synthetic brassinolide analogs

“…6c). On the contrary, Pereira-Netto et al (2006) did not observe any changes of BA level in Malus prunifolia (Wild) Borkh. after application of a synthetic brassinosteroid analog.…”