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[SANET-MG] alternate spling and GM crops
The article below shows that, like animals, plants engage in alternate
splicing extensively. In eukaryotes most genes are "split" they are
made up of exons, the DNA code for active protein domains separated by
introns which are spliced out as pre-messenger RNA exits the nucleus.
Many split genes can be spliced alternatively to create two or more
proteins for each gene sequence. Can alternate splicing influence the
transgenes of gm crops? There is , as yet , no answer to that question.
The commercial gm crops presently contain bacterial transgenes which are
"tuned" to fit the codon preference of the crop plant but the protein
codes are not interrupted with introns. However, plant introns are
usually added to the transgenes but just upstream of the translation
start signal, such introns are split from the pre-messenger RNA to
enhance movement of the message to the cytoplasm for translation. Thus
alternate splicing can , in theory, effect transgenes in plants but
that effect has not been reported in gm crops. The main reason seems to
be that it has not yet been studied.
Published online before print April 21, 2006
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0602039103
Bing-Bing Wang and Volker Brendel
Genomewide comparative analysis of alternative splicing in plants
Alternative splicing (AS) has been extensively studied in mammalian
systems but much less in plants. Here we report AS events deduced from
EST/cDNA analysis in two model plants: Arabidopsis and rice. In
Arabidopsis, 4,707 (21.8%) of the genes with EST/cDNA evidence show
8,264 AS events. Approximately 56% of these events are intron retention
(IntronR), and only 8% are exon skipping. In rice, 6,568 (21.2%) of the
expressed genes display 14,542 AS events, of which 53.5% are IntronR and
13.8% are exon skipping. The consistent high frequency of IntronR
suggests prevalence of splice site recognition by intron definition in
plants. Different AS events within a given gene occur, for the most
part, independently. In total, 36-43% of the AS events produce
transcripts that would be targets of the non-sense-mediated decay
pathway, if that pathway were to operate in plants as in humans. Forty
percent of Arabidopsis AS genes are alternatively spliced also in rice,
with some examples strongly suggesting a role of the AS event as an
evolutionary conserved mechanism of posttranscriptional regulation. We
created a comprehensive web-interfaced database to compile and visualize
the evidence for alternative splicing in plants (Alternative Splicing in
Plants, available at www.plantgdb.org/ASIP).
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