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-----Original Message-----
From: Takema Fukatsu [mailto:t-fukatsu@***.***]
Sent: Tuesday, September 16, 2003 12:15 PM
To: evolve@***.***; jfly@***.***; jeconet@ml.affrc@***.***;
tisa@***.***
Subject: [evolve:10697] 9/26 D.L.Stern seminar@***.***
EVOLVE, TISA, Jfly, jeconet readers 各位
＝＝＝＝＝セミナーのお知らせ＝＝＝＝＝
「ショウジョウバエ近縁種間における形態進化の分子発生学的基盤」
「アブラムシにおける単為発生プロセスおよび内部共生系の起源」
クロスポストご容赦ください。深津武馬＠産業技術総合研究所です。
米国プリンストン大学のDavid L. Stern 博士のセミナーを以下のようにおこな
いま
す。非常に広範な研究を展開している気鋭の研究者で、もともとは社会性アブラ
ムシ
類の進化生物学的研究で知られていましたが、最近ではショウジョウバエ近縁種
間の
形態的差異の分子基盤に関する研究を活発に展開しており、またアブラムシの単
為生
殖や多型性、共生微生物系などの分子発生学的基盤についての先駆的な研究もお
こなっ
ています。世界的に見ても指折りの「切れる」若手の進化生物学者と呼んでよい
でしょ
う。今回はショウジョウバエの話と、アブラムシの話を２題つづけて話していた
だけ
るようにお願いしました。関心のある方々の来聴を歓迎します。
演者：David L. Stern (Dept. Ecol. Evol. Biol., Princeton Univ., USA)
演題：
１）The morphological consequences of gene regulation microevolution in
Drosophila
２）Developmental origin and evolution of bacteriocytes in the
aphid-Buchnera symbiosis
日時：平成１５年９月２６日（金）１５時?
場所：産業技術総合研究所 つくば中央第６−１１ ２Ｆ会議室
くわしい場所、交通等については以下の産総研ホームページをご覧ください
http://www.aist.go.jp/aist_j/guidemap/tsukuba/tsukuba.html
講演要旨
１）The morphological consequences of gene regulation microevolution in
Drosophila
One of the most poorly understood components of evolution is how
genetic variation is translated into phenotypic variation (Stern, 2000).
We study this problem by working "backwards" from phenotypic differences
between species to the genetic changes that are responsible for these
differences. We are particularly interested in dissecting the
developmental pathways through which these genetic changes influence the
phenotype. We have identified several genes that evolved to generate
morphological change and these are some of the few morphological species
differences that have been mapped to single genes. We perform all of
this work in the genetic model system Drosophila melanogaster and its
close relatives, which provides an ideal opportunity to identify the
individual molecular events leading to morphological evolution. Several
years ago we determined that a major morphological difference between
two species of Drosophila, the presence or absence of most of the hairs
on the dorsum of the first-instar larva, was caused by evolution of a
single gene, ovo-shavenbaby (Sucena & Stern, 2000, PNAS). We recently
determined that three other cases of the evolution of the naked-larva
phenotype in the Drosophila genus all involve evolution of the
ovo-shavenbaby gene (Sucena et al., in press, Nature). That is,
morphological convergence sometimes involves evolution of the same gene,
even when the species are separated by 60 million years of evolution.
This work throws the whole concept of homology into suspicion. If
identical phenotypes can evolve by parallel evolution of the same gene,
how can we be sure that similar structures are really homologous
(derived from a common ancestor)? It seems that classical concepts of
homology are too restrictive and our contemporary understanding of gene
action renders the concept of homology tricky at best. [Refs]
*Sucena et al. (2003) Nature in press.
*Stern (2003) The Hox gene Ultrabithorax modulates the shape and size of
the third leg of Drosophila by influencing diverse mechanisms. Dev.
Biol. 256: 355-366.
*Sucena and Stern (2000) Divergence of larval morphology between
Drosophila sechellia and its sibling species caused by cis-regulatory
evolution of ovo/shaven-baby. PNAS 97: 4530-4534. *Stern (1998) A role
of Ultrabithorax in morphological differences between Drosophila
species. Nature 396: 463-466.
２）Developmental origin and evolution of bacteriocytes in the
aphid-Buchnera symbiosis
Symbiotic relationships between bacteria and insect hosts are common.
Although the bacterial endosymbionts have been subjected to intense
investigation, little is known of the host cells in which they reside ミ
the bacteriocytes. We have studied the development and evolution of
aphid bacteriocytes, the host cells that contain endosymbiotic bacteria,
Buchnera aphidicola. We show that bacteriocytes of Acyrthosiphon pisum
express several genes (or their paralogues): Distal-less,
Ultrabithorax/abdominal-A and Engrailed. Using these markers, we find
that a subpopulation of the bacteriocytes is specified prior to the
transmission of maternal bacteria to the embryo. In addition, we
discovered that a second population of cells is recruited to the
bacteriocyte fate later in development. We experimentally demonstrated
that bacteriocyte induction and proliferation occurs independently of B.
aphidicola. Major features of bacteriocyte development, including the
two-step recruitment of bacteriocytes, have been conserved in aphids for
80-150 MY. Furthermore, we have investigated two cases of evolutionary
loss of bacterial symbionts: in one case, where novel extracellular
(eukaryotic) symbionts replaced the bacteria, the bacteriocyte is
maintained; in another case, where symbionts are absent, the
bacteriocytes are initiated but not maintained.
The bacteriocyte represents an evolutionarily novel cell fate, which is
developmentally determined independently of the bacteria. A surprising
number of transcription factors (three out of five) show novel
expression patterns in bacteriocytes, suggesting that the bacteriocyte
may have evolved by co-opting expression of many additional
transcription factors. The evolutionary transition to a symbiosis in
which bacteria and an aphid cell form a functional unit, similar to the
origin of plastids, has apparently involved extensive molecular
adaptations on the part of the host cell. [Refs]
*Braendle et al. (2003) Developmental origin and evolution of
bacteriocytes in the aphid-Buchnera symbiosis. PLoS Biology in press.
*Miura et al. (2003) A comparison of parthenogenetic and sexual
embryogenesis of the pea aphid Acyrthosiphon pisum (Hemiptera:
Aphidoidea). J. Exp. Zool. 295B: 59-81.
深津 武馬
産業技術総合研究所 生物機能工学研究部門
生物資源情報基盤研究グループ 主任研究員
〒305-8566 茨城県つくば市東1-1-1 中央第６
E-mail: t-fukatsu@***.***
Tel. 029-861-6087 Fax. 029-861-6080
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