Aspects of DNA, RNA and protein synthesis during somatic embryogenesis in a carrot cell suspension culture

Changes in DNA, RNA and protein content, incorporation of ³H-thymidine, ¹⁴C-uridine and ³H-leucine and template activity of chromatin were investigated in the early process of somatic embryogenesis in a carrot (Daucus carota L. cv. Kurodagosun) cell suspension culture using a synchronous system. An embryogenetic culture in a medium containing 10^-7M zeatin was compared with a non-embryogenetic culture in a medium containing 10^-7M zeatin and 5 x 10^-7M 2,4-D. DNA was synthesized very actively prior to and during the formation of globular embryos in the embryogenetic culture. The RNA and protein content per tube increased at an almost constant rate in both cultures, while the rate of incorporation of labelled precursors of RNA and protein rose much more prior to active DNA synthesis in the embryogenetic culture than in the non-embryogenetic culture. Template activity of chromatin was high in the early stage of embryogenesis in the embryogenetic culture. The results obtained here showed that synthesis and turnover of RNA and protein became active prior to active DNA synthesis in the early stage of embryogenesis, and that these changes at macromolecular levels may play important roles in embryogenesis.     

Identification and characterization of microsatellite markers derived from expressed sequence tags (ESTs) of radish (Raphanus satvius L.)

Radish, Raphanus satvius, is a very important commercial crop in the world, especially in East Asian countries. In this study, radish microsatellite markers have been developed for the first time from expressed sequence tags (ESTs). A total of 8 primer pairs were able to produce clear amplifications, respectively, which gave 2–5 polymorphic loci between 43 cultivars of Japanese radish. Observed and expected heterozygosity ranged from 0 to 0.4186, and from 0.1779 to 0.6205, respectively. Polymorphic information content ranged from 0.171 to 0.575. The eight simple sequence repeats were also polymorphic when tested by wild radish (Raphanus raphanistrum). Deviation from Hardy–Weinberg equilibrium was analysed in three populations, and no linkage disequilibrium was observed. It is anticipated that these newly developed microsatellite markers can advance further genomic analyses. This accomplishment may in turn accelerate and simplify radish breeding programs.