Biology Reference
In-Depth Information
testis-specifi c
Dmrt1
mRNA has been found to be down-regulated in
the gonad of secondary male but
dax1
mRNA has been signifi cantly
up-regulated. In the protandric
Sparus aurata,
the Dmrt1 mRNA levels
are very low during testicular involution (Liarte et al., 2007).
(iii)
amh
: During gonadal differentiation of
A. schlegeli
, Wu et al. (2010)
have detected the expression of
amh
and
amh2
, the expression level
being higher in testicular tissue than in the ovarian tissue. There
was no difference in the levels of expression of
amh
and
amh2
during
active and inactive ovarian tissues. While the transcripts of
amh
are
expressed in somatic cells, spermatogonia and vitellogenic oocytes,
the expression of
amh2
is restricted to somatic cells of spermatogonia
alone. The testicular expression of
amh
remains high, when the
fi sh remains a male. Clearly, the
amh
is involved in regulation of
gametogenesis during both male and female phases of the porgy but
amh2
is more intimately involved in spermatogenesis.
(iv)
FTZ-F1
: Two
FTZ-F1
are homologues of mammalian
NR5A1
and
NR5A2
. In response to MT treatment for 40-60 days, the expression
of
FTZ-F1
decreases in the gonad but not in the pituitary. When
tested
in vitro
on ovarian tissues, MT does not affect the expression
of either
FTZ-F1
or
p450 aromA
, suggesting that the inhibition of
gonadal p450 aromatase and
FTZ-F1
may be mediated at the brain-
pituitary-gonadal axis (Zhang et al., 2007).
(iv)
TSHβ
: Its role in sex differentiation of
E. coioides
has been revealed
for the fi rst time but remains to be detected in other hermaphrodites.
EcTSHβ
mRNA is abundantly expressed and its expression level is
higher in the testis than in the ovary.
(v)
cyp
:
cyp19a1a
and endogenous estrogen play a critical role in natural
sex change. Progressively increasing expression levels of
cyp19a1a
have been reported from many protandrous species (e.g.,
Sparus
aurata,
Wong et al., 2006) and a reciprocal trend is observed in
protogynous species (e.g.,
E. akaara,
Li et al., 2006). The publications by
Lee et al. (2008) and Wu et al. (2008) have provided a detailed account
on the dynamic changes in the levels of
cyp19a1a
transcription and
protein in the male, intersex and female black porgy. The dynamic
changes in the levels from an undifferentiated gonad → differentiated
testis → transforming bisexual gonad and fi nally to functional ovary
suggest that
cyp19a1a
plays an important role in sex change from male
to female in the porgy. Lee et al. (2006) have shown that the expression
of
rmcyp19a
and
rmcyp19b
genes is differently modulated according
to estrogenic compounds and gender type of
K. marmoratus.
Liu et al. (2009) have cloned the key steroidogenic genes
p450 arom
and
p45011β
of
M. albus.
These genes show high homology to those
of other fi shes. The phylogenetic tree of
p45011β
cluster with the
