Abstract
In order to determine the role of polyamines in the formation and development of the somatic embryos of Capsicum chinense, the effect of different concentrations (0, 0.01, 0.1, and 1.0 mM) of Putrescine, Spermidine and Spermine on the efficiency and morphology of the embryos was evaluated. The results show that none of the three polyamines evaluated had a significant effect on the number of embryos formed, except Spermidine (1 mM), which caused a significant reduction in their numbers, in comparison with the control treatment. However, the most noteworthy result was observed in the treatment containing 0.1 mM of Spermine. The embryos developed in this treatment showed harmonic apex-radicle development, pale-green coloration and the formation of two tiny cotyledonary leaves. Real-time PCR was used to analyze the differential expression of the WUS, WOX1 and WOX3 genes in somatic embryos treated with Spermine and untreated, including the zygotic embryo. The transcript levels of the genes analyzed were found to differ significantly between both types of embryos (somatic and zygotic), with the zygotic embryos presenting a higher level of transcripts; however, compared to the untreated somatic embryos, the somatic embryos treated with Spermine showed an increase in the transcript levels of the three genes analyzed (WUS, WOX1 and WOX3); the WOX1 gene in particular presented an accumulation pattern similar to that of the zygotic embryo of the species. Key words: Somatic embryos, zygotic embryos, polyamines, transcript patterns and morphology.
Highlights
Somatic embryogenesis (SE) is defined as a process in which a bipolar structure develops from a non-zygotic cell without vascular connection with the origin tissue (Merkle et al, 1995)
The shoot apical meristem (SAM) and cotyledons of higher plants are established during embryogenesis in the apex (Jurgens et al, 1995)
204 bp the treatments evaluated (Figure 1A to C), while the addition of Spd causes a marked decrease in the efficiency along with the increase of the Spd concentration, with significant differences when compared to the control treatment
Summary
Somatic embryogenesis (SE) is defined as a process in which a bipolar structure develops from a non-zygotic cell without vascular connection with the origin tissue (Merkle et al, 1995). Three categories of malformations have been described for somatic embryos of different species: fused embryos (Carraway and Merkle, 1997; Rodriguez and Wetzstein, 1994; Stipp et al, 2001); altered cotyledon morphology (Carraway and Merkle, 1997; Jayasankar et al, 2002); and lack of a shoot (abnormal apical meristem histodifferentiation) (Chengalrayan et al, 2001; Jayasankar et al, 2002; Stipp et al, 2001) High frequencies of these abnormalities and the most critical defect, the absence of a shoot in the regenerants have been reported in the Capsicum sp. The metalized samples were observed using a JSM-6360LV JEOL scanning electron microscope
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