Annual Report 2006

nucleotide diversity of molybdenum cofactor
sulfrase () gene using 15
regional races. We also estimated that of
mitochondrial 1 gene and comparatively
analyzed these results. To detect transposition
event of MITE-like transposon,
we carry out excision assay on
specific insertion sites.
Genetics and evaluation of
silkworm stocks
Bisexually reproductive tetraploid strains
were established with high fertility in the
. It was reconfirmed that the
female sex was determined by the presence of
W chromosome in the tetraploid and triploid
offspring of the strains. Our database search of
the deleted sequence found in one of the
intersex strain, showed no significant
homology to the previously registered genes. In
normal cells we detected fragments of mRNA
transcribed from the deleted region, but it was
difficult to clone full length mRNA. We obtained
BAC clones contain the deleted sequence. The
female specific splicing of gene was
increased in the cultured male cells transfected
with one of these BAC clones. Mapping of
homeotic mutant genes was examined by a
three-point test. Three homeotic mutant genes
belonging to -pseudoalleles and
and were arranged in order from the
proximal side of the sixth linkage chromosome.
The new mutant gene, maternal brown egg of
Shimizu ( ) was confirmed to be a novel
mutant as a member of recessive pseudoalleles
in the .
As a trial in order to develop longterm
preservation of silkworm eggs, ovary
transplantation using fourth instar larva of
silkworm was technically too difficult to keep
alive. A correlation between total amount of
sugar alcohols contained in eggs and viability in
two-years preservation of silkworm eggs was
low score.
Insect-plant interactions
We have cloned a cDNA for laccase from
the salivary glands of the green rice leafhopper,
While many insect
laccases have been identified in cuticle, we
know only an example of laccase of salivary
gland origin. To characterize the enzymological
properties, we expressed a salivary laccase as a
recombinant protein. cells harboring the
expression plasmid produced laccase as a
soluble protein in the cytoplasms. Laccase
acitvity was detected when copper chloride
was added to culture medium, suggesting
the presence of a cupper center essential for
the oxidase activity.
We have started to isolate brown
planthopper resistant genes from rice using
map-based cloning method. Norin PL10 has a
resistance gene ( ) which is originated
from a Sri Lanka variety Rathu Heenati. The
chromosome segment of Rathu Heenati was
found in the chromosome 4 of Norin PL10,
between the two SSR (Simple Sequence Repeat)
makers, RM6487 and RM3735.
We found that the latex of a wild fig
species, that grows in Ishigaki
Island, Okinawa, showed a strong toxicity to
the Eri silkworm, When the Eri
silkworms were fed the artificial diet containing
2% of mulberry latex, growth inhibition was
observed, and when the diet containing more
than 10% of mulberry latex was fed, high
mortalities were observed. We also discovered
that the mulberry leaves are toxic to insect
except the silkworm, , and that
the latex ingredients, three sugar mimic
alkaloids, which are well known as glycosidase
inhibitors, and unknown high-molecular-weigh
factor(s) are responsible for the defense of
mulberry leaves against herbivorous insects.
Natural enemies
is one of the most
important predators of spider mites of the
genus in Japan. We found that
learns a specific blend of several
volatiles emitted from prey-infested plants and
is attracted to the volatile complex. The
predatory mite has intra-specific variation in its
olfactory response. The predator showing
strong olfactory response could reach preyinfested
plants more efficiently than the mites
with weak olfactory responses did. Genetic