Jerzy Paszkowski

Recognition efficiency of Dicotyledoneae-specific promoter and RNA processing signals in rice

SummaryHeterologous gene expression experiments have shown that genes ofMonocotyledoneae are often not transcribed inDicotyledoneae, or produce pre-mRNA that is inefficiently or aberrantly processed. It is however not known how correctly and efficiently dicotyledon-specific gene expression signals are recognized in cells ofMonocotyledoneae. Here we address this question using tobacco (Nicotiana tabacum) and rice (Oryza sativa) protoplasts transformed with the same hybrid gene constructs. Constructs including thenptII protein coding sequence fused to Cauliflower Mosaic Virus (CaMV) promoter and polyadenylation signals were used to obtain stably transformed cell lines of tobacco and rice. In one of the constructs thenptII coding region is interrupted by a modified intron-3 sequence from the soybean phaseolin gene. Although the mean number of hybrid gene copies integrated into the rice genome was on average 5- to 10-fold higher than in tobacco, the steady-state transcript level was 3 times lower. A lower level of transcript was also observed in transient expression experiments. The amount of the mature mRNA was not influenced by the presence of the intron. The phaseolin intron was processed in rice with high efficiency and an accuracy indistinguishable from that seen in tobacco.

Intrachromosomal Recombination Between Genomic Repeats

Three types of homologous recombination (HR) in plants are reviewed in this book: n n nextrachromosomal recombination (ECR) between input DNAs, either viral replicons (reviewed in chapter 2), or non-replicating input DNAs (chapter 5); n n nrecombination between input (extrachromosomal) DNA and a chromosomally located target DNA sequence, i.e. gene targeting (GT), either of the nuclear genome (chapter 9) or chloroplast genomes (chapter 4); and n n nintrachromosomal recombination (ICR) of the chloroplast (chapter 4), mitochondrial (chapter 3) or nuclear genomes that we review in this chapter.

Fate of Foreign DNA Introduced to Plant Cells

The use of genetic transformation for the introduction of foreign genes into higher plants already has a history of more than five years (1,2). The development of Agrobacterium tumefaciens as a gene carrier to plant cells substantially stimulated the progress of experimental plant molecular biology and also the development of alternatives to Agrobacterium for gene transfer to plants. The construction of hybrid selectable marker genes and the establishment of clean selection systems for the transformed phenotype allowed rapid progress of new methods for delivery of foreign DNA.