Splicing signals and factors in plant intron removal.
Constitutive splicing of the potato invertase mini-exon 2 (9 nt long) requires a branchpoint sequence positioned around 50 nt upstream of the 5' splice site of the adjacent intron and a U(11) element found just downstream of the branchpoint in the upstream intron [Simpson, Hedley, Watters, Clark, McQuade, Machray and Brown (2000) RNA 6, 422-433]. The sensitivity of this in vivo plant splicing system has been used to demonstrate exon scanning in plants, and to characterize plant intronic elements, such as branchpoint and poly-pyrimidine tract sequences. Plant introns differ from their vertebrate and yeast counterparts in being UA- or U-rich (up to 85% UA). One of the key differences in splicing between plants and other eukaryotes lies in early intron recognition, which is thought to be mediated by UA-binding proteins. We are adopting three approaches to studying the RNA-protein interactions in plant splicing. First, overexpression of plant splicing factors and, in particular, UA-binding proteins, in conjunction with a range of mini-exon mutants. Secondly, the sequences of around 65% of vertebrate and yeast splicing factors have high-quality matches to Arabidopsis proteins, opening the door to identification and analysis of gene knockouts. Finally, to discover plant-specific proteins involved in splicing and in, for example, rRNA or small nuclear RNA processing, green fluorescent protein-cDNA fusion libraries in viral vectors are being screened.
Brown
J W S
JW
Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, Scotland, U.K. jbrown@scri.sari.ac.uk
Simpson
C G
CG
Thow
G
G
Clark
G P
GP
Jennings
S N
SN
Medina-Escobar
N
N
Haupt
S
S
Chapman
S C
SC
Oparka
K J
KJ
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D005091:Exons; D017343:Genes, Plant; D006026:Glycoside Hydrolases / Q000235:genetics; D006801:Humans; D007438:Introns; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D010944:Plants / Q000235:genetics* / Q000378:metabolism*; D012326:RNA Splicing; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D011198:Solanum tuberosum / Q000235:genetics / Q000378:metabolism; D043324:beta-Fructofuranosidase
D009687:Nuclear Proteins; D010940:Plant Proteins; D018749:RNA, Plant; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase