Abstract
SummaryPartial desiccation treatment (PDT) stimulates germination and enhances the conversion of conifer somatic embryos. To better understand the mechanisms underlying the responses of somatic embryos to PDT, we used proteomic and physiological analyses to investigate these responses during PDT in Picea asperata. Comparative proteomic analysis revealed that, during PDT, stress‐related proteins were mainly involved in osmosis, endogenous hormones, antioxidative proteins, molecular chaperones and defence‐related proteins. Compared with those in cotyledonary embryos before PDT, these stress‐related proteins remained at high levels on days 7 (D7) and 14 (D14) of PDT. The proteins that differentially accumulated in the somatic embryos on D7 were mapped to stress and/or stimuli. They may also be involved in the glyoxylate cycle and the chitin metabolic process. The most significant difference in the differentially accumulated proteins occurred in the metabolic pathways of photosynthesis on D14. Furthermore, in accordance with the changes in stress‐related proteins, analyses of changes in water content, abscisic acid, indoleacetic acid and H2O2 levels in the embryos indicated that PDT is involved in water‐deficit tolerance and affects endogenous hormones. Our results provide insight into the mechanisms responsible for the transition from morphologically mature to physiologically mature somatic embryos during the PDT process in P. asperata.
Highlights
The complete process of the vegetative propagation technique, somatic embryogenesis, in conifer includes embryonic callus initiation, proliferation, somatic embryo maturation and germination (Stasolla and Yeung, 2003)
Partial desiccation treatment that caused a gradual and limited loss of moisture content in conifer somatic embryos was first reported by Roberts (Roberts et al, 1990)
Some physiological and metabolic changes during partial desiccation treatment (PDT) have been reported in conifer somatic embryos (Dronne et al, 1997; Find, 1997; Kong and Yeung, 1995; Stasolla et al, 2001)
Summary
The complete process of the vegetative propagation technique, somatic embryogenesis, in conifer includes embryonic callus initiation, proliferation, somatic embryo maturation and germination (Stasolla and Yeung, 2003). Among these phases, germination/conversion is regarded as the most important step to obtain plantlets; this determines the success of this technique.
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