Abstract
The in planta transformation method was used for mulberry plants [Morus alba L., F1 generation obtained by natural pollination of a Chinese variety, Canzhuan No.4 (female)]. For transformation, an avirulent mutant of Agrobacterium tumefaciens (M-21), isolated by us, was used; the mutant is capable of integrating its T-DNA into chromosomes of host plants but produces no galls since a gene (tryptophan monooxygenase gene, iaaM) involved in auxin (indole acetic acid, IAA) biosynthesis in the T-DNA region is destructed by transposon5 (Tn5) insertion. All other genes including the ipt gene for cytokinin biosynthesis in the T-DNA region are intact. Young mulberry trees in pots were decapitated and meristems of axillary buds were inoculated by water suspension of A. tumefaciens after being pricked with a needle. The inoculated four plants were allowed to grow in pots. All of the four transformants in the T0 generation showed characteristic phenotypes different from those of non-transformed plants, which seemed to be due to overproduction of cytokinin. The transgene (Tn5-inserted T-DNA) was detected in all of four transformants by nested PCR. The offspring of transformants (T0) produced by stem cuttage also showed remarkable phenotypes different from those of offspring of non-transformed plants. The transgene was transmitted in all of the offspring of transformants. Thus, the transgenic mulberry plants can be produded simply and efficiently by the in planta transformation method as detailed in this paper.
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