CHLOROPLAST DIFFERENTIATION IN SOMATIC EMBRYOS OF CARROT - EFFICIENCY OF BLUE AND RED-LIGHT IRRADIATION ON GENE-EXPRESSION

In young somatic embryos of Daucus carota the differentiation of chloroplasts is preferentially induced and maintained by blue light. During this greening process the steady-state concentration of mRNAs encoding prominent chloroplast proteins increases rapidly in response to blue light irradiation as evaluated by Northern hybridization analyses employing cloned sequences of the corresponding genes as probes. Red light cannot adequately replace blue light neither in induction nor in maintaining chloroplast development. From a group of novel genes which are apparently involved in the initiation of somatic embryogenesis of carrot cells at least one is rapidly and transiently expressed at the onset of blue light-induced chloroplast differentiation. Its coding sequence which specifies a glycine-rich protein of 14 111 Da with a unique domain structure shares a high degree of homology with a gene identified in suspension-cultured cells of Chenopodium rubrum; it belongs to a group of novel genes which are induced by blue light during the initial phase of chloroplast differentiation.