Annual Report 2006

Fig. 1
Gene structures and mutations of the -like genes in rice
(A) Boxes and horizontal lines indicate exons and introns. Black triangles show the positions of deleted nucleotides
in YM-15 and G-52. White triangles indicate the insertion positions of . Hatched and crossed boxes indicate
the location of the putative Rieske center binding motif and mononuclear iron-binding motifs. (B) Rieske binding and
mononuclear iron-binding motifs in CAO. Residues in the binding domain are boxed. A substitution form Y to F in
CAO-11 is shaded. The deleted residue in CAO-09 of G-52 is underlined.
retrotransposon -induced mutants that
disrupt these two CAO-like genes within the
insertion mutant database. We found
three mutants (ND0017, NE1005, ND3004) of
and one (ND1064) of We
selected plants homozygous for each allele and
analyzed their phenotypes. Consistent with the
analysis of YM-15 and G-52, homozygotes of
all three mutations for showed pale
green phenotype and lacked Chl . On the other
hand, the homozygotes of the mutation
did not show a pale green phenotype and
contained a normal level of Chl content.
has an incomplete Rieske binding motif, in
which the highly conserved tyrosine residue (Y)
among proteins containing Reiske binding sites
is replaced with phenylalanine (F), suggesting
that is a pseudogene. The 3-bp deletion
in of G-52 results in a deletion of the
lysine residue (K), which is located in the
mononuclear iron-binding site in CAO. This
residue is not necessarily highly conserved in
proteins containing mononuclear-iron-binding
sites, but is limited to arginine or lysine, both of
which are positively charged amino acids,
among CAOs of distantly related species.
Complete loss of Chl in G-52 suggests that this
positively charged residue is important for
CAO activity or stability.
The rice genome is estimated to have
many duplicated genes, which are thought to
have redundant functions. However, the
example described here suggests that not
many of such genes are functionally redundant,
even if they are expressed.
Comparison of the Mutation
Inducing Effect between Ion
Beams and Gamma Rays
Mutation induction is a useful method for
plant breeding and the type of mutagenic
treatment is an important factor for successful