Search Results
A Lycopersicon esculentum Mill. (tomato) cDNA clone with high similarity to a Nicotiana plumbaginifolia Viv. (tobacco) cytochrome P450 gene was isolated using 5' and 3' rapid amplification of cDNA ends (RACE). The isolated cDNA (GenBank Accession No. AF249329) has an open reading frame of 1494 base pairs (bp) and encodes a protein of 498 amino acids with 75% identity to the N. plumbaginifolia cytochrome P450 (CYP72A2) and 45% to a Catharanthus roseus G. Don (Madagaskar periwinkle) CYP72A1 protein sequence. By Southern-blot analysis, one or two highly homologous genes were detected in the L. esculentum genome. Expression of the cloned P450 gene was regulated by circadian rhythm and enhanced by wounding. Leaf transcripts were detected in the light but not dark. Highest transcript levels were observed 3 hours after mechanical wounding. No increase in expression was seen in response to applications of zeatin as with the N. plumbaginifolia gene. Of the tissues analyzed, shoot tips and young leaves and fruit had the highest detectable transcript levels. Attempts to transform more than 1400 cotyledon explants of L. esculentum with sense or antisense CYP72A2 gene constructs produced no transgenic plants.
Abstract
Plant growth regulator studies and plant tissue culture research have been closely related and mutually supportive. The manipulation of plant cells, tissues, and organs in culture, with important applications in propagation and genetic modification of plants, is highly dependent on the use of appropriate growth regulator regimes. Conversely, tissue culture systems are useful as bioassays to define the growth-regulating activity of many compounds. The discovery of the cytokinin N-(2-furanylmethyl)-1H-purin-6-amine (kinetin) by Miller et al. (17) was particularly relevant in this respect. Whereas the testing of this cytokinin and its structural analogues for biological activity was dependent on callus culture bioassays, the subsequent availability of synthetic cytokinins created many new opportunities in the field of plant tissue culture.