AGROBACTERIUM-MEDIATED TRANSFORMATION OF POPLAR USING A DISARMED BINARY VECTOR AND THE OVEREXPRESSION OF A SPECIFIC MEMBER OF A FAMILY OF POPLAR PEROXIDASE GENES IN TRANSGENIC POPLAR CELL

An efficient method was established for transformation of the poplar hybrid Populus kitakamiensis (Populus sieboldii x Populus gradidentata) using a binary disarmed strain of Agrobacterium tumefaciens LBA4404 and Ti-binary vectors, The frequency of transformation of poplar leaf segments reached as high as 60%. In transgenic pop]ar plants, the gene for beta-glucuronidase (gus) was expressed at high levels under the control of the cauliflower mosaic virus 35S (CaMV35S) promoter. Poplars possess a number of peroxidase isozymes whose pattern of expression is tissue-specific, developmentally regulated and influenced by environmental factors. We altered the expression of a peroxidase isozyme by introducing an identified genomic gene for a peroxidase (prxA1) under the control of the CaMV35S promoter. Transgenic poplars obtained by introducing the chimeric peroxidase gene (CaMV35S promoter-prxA1) were shown to have an increase in total peroxidase activity that was accounted for by the specific overproduction of the peroxidase isozyme (PrxA1). From this study,the anionic peroxidase isozyme encoded by the identified genomic gene, prxA1, was demonstrated to be the anionic peroxidase isozyme with a pI of 4.4 among various isozymes of poplar peroxidase. On the basis of this assignment, we characterized the tissue-specific and UV-light-inducible regulation of expression of this isozyme.