Shoot regeneration and the relationship between organogenic capacity and endogenous hormonal contents in pumpkin

Abstract

To induce multiple shoots from pumpkin (Cucurbita moschata Duch.), cotyledon explants excised from various ages of seedlings after in vitro germination were cultured on MS augmented with different concentrations of BA (0, 0.5, 1.0 or 2.0 mg l -1 ). The highest frequency of shoot regeneration (63.7%) was observed from seven-day-old cotyledon explants cultured on MS containing 0.5 mg l -1 BA. The frequency and duration of shoot formation showed close correlation with the donor seedling age. By contrast, BA supply was necessary to promote shoot formation but no differences were observed in relation to different concentrations. Multiple shoots elongated on MS supplemented with 0.1 mg l -1 BA and 5-7 shoots per regenerated explant were recovered. Elongated shoots were rooted on MS, which was easier than that on 2/3MS, 1/2MS, or MS supplemented with 0.1 mg l -1 NAA. The rooted shoots were then transferred to greenhouse where they grew and flowered normally. Quantitative analysis of endogenous auxin (IAA) and cytokinins (iPA and ZR) in initial cotyledon explants of different aged seedlings showed that the regeneration ability of cotyledon explants varied dependently on their endogenous iPA contents. This study therefore deduces that the various organogenic capabilities of cotyledon explants from pumpkin are the result of their endogenous hormonal contents.

Osmotic stress stimulates shoot organogenesis in callus of rice (Oryza sativa L.) via auxin signaling and carbohydrate metabolism regulation

“…Plantlets can be regenerated from rice callus via both somatic embryogenesis and organogenesis but mainly through organogenesis Huang et al 2006). Exogenous PGRs, especially auxins, applied to induce shoot regeneration, interact with endogenous tissuespecific hormones; thus, the level of endogenous hormones in cultured explants and derived callus are considered the most important factor in shoot regeneration (Valdés et al 2001;Souza et al 2003;Zhang et al 2008;Huang et al 2012). However, most rice cultivars have low regeneration ability (\5 %) with calli derived from MS basal medium containing 2,4-D alone in CIM .…”

“…The initiation of regeneration from callus may be related to the balance between auxin and cytokinin. Although the exact nature of these hormonal signals may vary between species, the balance in auxin to cytokinin has a consistent effect on the type of regenerated organs (Charriére et al 1999;Sugiyama 1999;Fernando and Gamage 2000;Mercier et al 2003;Jiménez 2005;Zhang et al 2008). In addition, the effect of added auxins and cytokinins has been related to an interaction with other endogenous hormones such as ABA, thus leading to conspicuous changes in development (Lakshmanan and Taji 2000).…”

“…Many studies have shown the effects of PGRs on tissue culture (Jiménez 2005;Yin et al 2008;Zhang et al 2008;Barreto et al 2010;Feng et al 2010;Huang et al 2012). Auxin and cytokinin are considered key factors to shoot differentiation in callus culture (Skoog et al 1965;Pernisová et al 2009;Su et al 2009;Cheng et al 2010;Vanneste and Friml 2009;Zhao et al 2010).…”

Improving the transformation efficiency of Cucurbita species: factors and strategy for practical application

“…In species belonging to the family Cucurbitaceae, a proximal region of cotyledon with a cotyledonary node is required for regeneration and transformation because regeneration is observed only in a tiny area between cotyledon and hypocotyl (Ananthakrishnan et al 2003;Han et al 2004;Lee et al 2003;Mohiuddin et al 1997;Nanasato et al 2011;Tabei et al 1993;Zhang et al 2008). One of the important factors in organogenic potential is explant age.…”

“…Earlier studies reported regeneration of Cucurbita species via embryogenesis from cotyledons (Jelaska 1972). Direct organogenesis has been developed with high efficiency (>50%) using proximal regions of cotyledonary explants (Ananthakrishnan et al 2003;Kim et al 2010;Lee et al 2003;Zhang et al 2008). However, these species are known to be one of the plants most refractory for transformation.…”