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Abstract Background Somatic embryogenesis in spruce is a process of high importance for biotechnology, yet it comprises of orchestrated series of events whose cellular and molecular details are not well understood. In this study, we examined the role of actin cytoskeleton during somatic embryogenesis in Norway spruce line AFO 541 by means of anti-actin drugs. Results Application of low doses (50-100 nM) of latrunculin B (Lat B) during the maturation of somatic embryos predominantly killed suspensor cells while leaving the cells in meristematic centres alive, indicating differential sensitivity of actin in the two cell types. The treatment resulted in faster development of more advanced embryos into mature somatic embryos and elimination of insufficiently developed ones. In searching for the cause of the differential actin sensitivity of the two cell types, we analysed the composition of actin isoforms in the culture and isolated four spruce actin genes. Analysis of their expression during embryo maturation revealed that one actin isoform was expressed constitutively in both cell types, whereas three actin isoforms were expressed predominantly in suspensor cells and their expression declined during the maturation. The expression decline was greatly enhanced by Lat B treatment. Sequence analysis revealed amino-acid substitutions in the Lat B-binding site in one of the suspensor-specific actin isoforms, which may result in a different binding affinity for Lat B. Conclusions We show that manipulating actin in specific cell types in somatic embryos using Lat B treatment accelerated and even synchronized the development of somatic embryos and may be of practical use in biotechnology.

Background: Somatic embryogenesis in spruce is a process of high importance for biotechnology, yet it comprises of orchestrated series of events whose cellular and molecular details are not well understood. In this study, we examined the role of actin cytoskeleton during somatic embryogenesis in Norway spruce line AFO 541 by means of anti-actin drugs. Results: Application of low doses (50-100 nM) of latrunculin B (Lat B) during the maturation of somatic embryos predominantly killed suspensor cells while leaving the cells in meristematic centres alive, indicating differential sensitivity of actin in the two cell types. The treatment resulted in faster development of more advanced embryos into mature somatic embryos and elimination of insufficiently developed ones. In searching for the cause of the differential actin sensitivity of the two cell types, we analysed the composition of actin isoforms in the culture and isolated four spruce actin genes. Analysis of their expression during embryo maturation revealed that one actin isoform was expressed constitutively in both cell types, whereas three actin isoforms were expressed predominantly in suspensor cells and their expression declined during the maturation. The expression decline was greatly enhanced by Lat B treatment. Sequence analysis revealed amino-acid substitutions in the Lat B-binding site in one of the suspensorspecific actin isoforms, which may result in a different binding affinity for Lat B. Conclusions: We show that manipulating actin in specific cell types in somatic embryos using Lat B treatment accelerated and even synchronized the development of somatic embryos and may be of practical use in biotechnology. [ABSTRACT FROM AUTHOR]

The broad-toothed field mouse (Apodemus mystacinus) is distributed throughout the Balkan Peninsula, Asia Minor and the Middle East. It is generally split into two different specific entities:Apodemus epimelasoccurs on the Balkan Peninsula andA. mystacinusinhabits Asia Minor and the Middle East. This analysis, based on two mitochondrial regions (cytochromeband the D-loop) and theinterstitial retinol binding protein (IRBP)nuclear gene, confirms an important level of genetic divergence between the animals from these regions and their separation from each other at least 4.2–5.1 Mya, which is in favour of a distinct specific status. Finally, the broad-toothed field mice from south-western Turkey appear to be closely related to the animals from Crete but highly distinct from the populations of the other Oriental regions. This supports a distinct subspecific level (A. m. rhodius) for the insular animals and also for those from south-western Turkey. From a biogeographical point of view, it can be assumed that either late Pliocene or early Pleistocene cooling led to the isolation of two main groups ofA. mystacinus, one in the Balkan region and the other one in Turkey and the Near East (Syria and Israel). In this region, it is suggested that a more recent event appeared during the Quaternary period, isolating broad-toothed field mice in Crete and leading to the appearance of two well-differentiated genetic groups: one in Crete and south-western Turkey, and the other widespread in northern and eastern Turkey as well as in the Near East. © 2005 The Linnean Society of London,Biological Journal of the Linnean Society, 2005,85, 53–63. [ABSTRACT FROM AUTHOR]