Phytosulfokine Stimulates Somatic Embryogenesis in Cryptomeria japonica

Abstract

; Phytosulfokine (PSK), which has been identified as a plant growth factor, had a dramatic stimulatory effect on the formation of somatic embryos of sugi (Cryptomeria japonica) in the presence of polyethylene glycol. The resultant somatic embryos germinated with synchronous sprouting of cotyledons, hypocotyls and roots, and most of the seedlings grew normally. A cDNA clone for the precursor to the PSK peptide of C. japonica was identified in an expressed sequence tags database. Our results support the existence of a PSK signaling pathway in C. japonica.

Plant regeneration from leaf-derived protoplasts within the Daucus genus: effect of different conditions in alginate embedding and phytosulfokine application

“…This may suggest that the applied concentration of PSK was too low for these two accessions to promote sustained division of the protoplast-derived cells, while for the remaining Daucus species, it was sufficient to stimulate a higher level of somatic embryogenesis, since four-fold fewer plants were regenerated from PSK-free cultures. Similar promotion of somatic embryogenesis as a result of PSK supplementation was observed in suspension cultures of plants as diverse as carrot (dicotyledons) and Cryptomeria japonica (conifers) (Hanai et al 2000;Igasaki et al 2003).…”

“…Since PSK is involved in nanomolar concentrations in the initial steps of cellular dedifferentiation, proliferation, and re-differentiation, its biological function is similar to that of plant hormones (Igasaki et al 2003;Matsubayashi et al 2004). PSK can not only induce cell division in suspension and protoplast cultures (Matsubayashi and Sakagami 1996;Matsubayashi et al 1997), but appears to play a role in diverse aspects of plant development and reproduction, including the formation of tracheary elements and adventitious roots (Yamakawa et al 1998;Matsubayashi et al 1999), somatic embryogenesis (Kobayashi et al 1999;Igasaki et al 2003), and pollen germination (Chen et al 2000). It seems that besides the widely used auxins and cytokinins, PSK can be a promising supplement for in vitro plant cultures, especially in the case of recalcitrant species.…”

Early studies on the effect of peptide growth factor phytosulfokine-α on Brassica oleracea var. capitata L. protoplasts

“…Studies on A. thaliana hypocotyl-derived protoplasts showed that PSK signaling controls osmotically-driven cell expansion suggesting that PSK-α acts as an osmoregulator and involves K + uptake [27]. It has been reported that PSK-α plays an important role in plant growth and development due to its contribution to the formation of somatic embryos [28,29], its role in adventitious buds and roots formation [25,30], and its contribution to cellular longevity and the cell division cycle [31,32]. The objective of this study was to analyze the effect of PSK-α on viability and division frequencies of Brassica oleracea protoplast-derived cells embedded in calcium alginate layers.…”

Development of the embryo proper and the suspensor during plant embryogenesis

“…The concentration of PSK in this culture was 3.3 nM. In gymnosperms, somatic embryogenesis in Cryptomeria japonica is stimulated by PSK (Igasaki et al 2003), and PSK precursor gene has been identified in C. japonica (Igasaki et al 2003). In an attempt to characterize the role of PSK in gymnosperm embryogenesis, we examined the effects of PSK on somatic embryogenesis of Japanese larch using the culture system established by Ogita et al (1997Ogita et al ( , 1999, which is relatively straightforward to induce somatic embryos (comprising the embryo proper and the suspensor), and plantlets can be regenerated readily (Figure 3).…”