QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 15 October 2003
doi: 10.1242/dev.00835

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Copf, T. Articles by Averof, M. Search for Related Content PubMed PubMed Citation Articles by Copf, T. Articles by Averof, M.

Posterior patterning genes and the identification of a unique body region in the brine shrimp Artemia franciscana

¹ Institute of Molecular Biology and Biotechnology (IMBB-FORTH), Vassilika Vouton, 71110 Iraklio Crete, Greece
² Laboratoire de Biologie du Développement, Université Paris 7, 7 quai St Bernard, 75005 Paris, France
³ Berkeley Drosophila Genome Project, Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720, USA

View larger version (77K): [in a new window]   Fig. 1. Larval development and establishment of the body plan in Artemia. (A) Schematic representation of the early stages of larval development in an anostracan crustacean, corresponding roughly to stages L1, L2, L4, L6 and L8 of Artemia development. Body segments are generated sequentially from the growth zone (in grey) during larval development. (B) The adult body plan of Artemia consists of the head, 11 thoracic/trunk segments, two genital segments, six post-genital segments and the telson. (C,D) Scanning electron micrographs of the Artemia growth zone showing the outline of individual ectodermal cells, shortly before hatching (C) and during stage L3 (D). The growth zone is characterised by the regular arrangement of these undifferentiated ectodermal cells into columns. (E) Engrailed expression in the post-genital segments; Engrailed protein can be detected in a narrow stripe at the posterior of each segment. (F) The musculature of a fully segmented Artemia, seen using polarised light microscopy. The post-genital segments (labelled PG) have a characteristic pattern of muscles that is distinguishable from that of other trunk segments.

View larger version (104K): [in a new window]   Fig. 2. Expression of AbdB in Artemia. (A) Early AbdB expression in the two genital segments, shortly after these segments have formed (stage L9). (B) Later, stronger AbdB expression restricted to the two genital segments (stage L11). (C) Late expression of AbdB (after stage L13) persists in the differentiated genital segments and also extends anteriorly to cells of posterior thoracic/trunk segments. AbdB expression is never seen posterior to the genital segments. Anterior is upwards.

View larger version (59K): [in a new window]   Fig. 3. Sequence alignments among Cad/Cdx, Eve/Evx and Sal homologues from Artemia and diverse species. Amino acid sequence alignments confirm that we have cloned orthologues of the Cad/Cdx, Eve/Evx and Sal genes, respectively. Only significantly conserved regions are shown, with conserved amino acids highlighted in grey. Sequence Accession Numbers: AJ567452 (AfCad), AJ567453 (AfEve), AJ567454 (AfSal).

View larger version (56K): [in a new window]   Fig. 4. Expression patterns of Cad and Eve homologues in Artemia. (A,B) Immunochemical stainings with antibodies against AfCad and AfEve in newly hatched nauplii, showing expression of both genes in the posterior growth zone that will generate most body segments. AfEve shows additional expression in a single-cell wide segmental stripe (large arrowhead) and in the hindgut (small arrowhead). (C) Distribution of AfCad mRNA in an early larva (stage L2), visualised by in situ hybridisation. (D) Distribution of AfCad protein during the same stage, visualised by immunochemical staining. AfCad mRNA and protein distributions appear the same. (E) Magnification of the anterior boundary of expression of AfCad in the growth zone, showing two zones expressing different levels of AfCad protein. The zone with lower levels of AfCad is seen only in some individuals and is presumed to be a transient feature. (F) Magnification of the anterior boundary of expression of AfEve, including a single segmental stripe that has separated from the growth zone. This stripe is only seen in some individuals, and is thought to appear very transiently. (G) Double immunochemical staining with antibodies against Ubx and AbdA (in purple), and AfCad (in dark red), showing overlap of their expression domains over one or two segments (bracket). (H) Double immunochemical staining with antibodies against Engrailed (in blue) and AfEve (in red). The stripe of AfEve expression disappears before the onset of Engrailed expression. Expression of AfEve can be seen in the growth zone, in a transient segmental stripe (large arrowhead) and in specific cells in the CNS (small arrowheads). Ventral views, anterior towards the top.

View larger version (82K): [in a new window]   Fig. 5. Expression of AfCad and development of the anal appendages in Artemia. (A) Immunochemical staining with an antibody against Dll, showing the early expression of Dll in the anal structures (arrowhead), in stage L6. Dll expression is also seen in the first few thoracic appendages that have formed at this stage. (B) Scanning electron micrograph of the anal region in stage L6-7. (C) Immunochemical staining showing the earliest expression of AfCad in the anal structures (arrowhead) at stage L6. Expression is still seen in the growth zone (bracket). (D) Immunochemical staining for Dll in a fully-segmented larva (around stage L11). Dll expression is seen in the caudal furca (arrowhead), in the thoracic appendages and in the two genital segments (bracket). No Dll expression is seen in the post-genital segments. (E) Scanning electron micrograph of the anal region in stage L11. (F) Immunochemical staining showing the late expression of AfCad in the caudal furca (around stage L11).

View larger version (102K): [in a new window]   Fig. 6. Mis-expression of AfCad in Drosophila. (A) Ectopic anal plates in the dorsal head cuticle of a fly caused by mis-expression of AfCad using the MS-248 GAL4 driver. The anal plates are characterised by being darkly pigmented, having no trichomes and carrying long wavy bristles. (B) Ectopic activation of Dll-lacZ following mis-expression of AfCad using the MS248 driver. Dll is activated in an ectopic patch of cells (arrowhead) close to the normal domain of Dll expression in the antennal primordium. (C) Ectopic activation of Byn-lacZ in the wing disc, following mis-expression of AfCad using the apterous-GAL4 driver. Byn is induced in two patches of cells at the lateral edges of the wing pouch.

View larger version (25K): [in a new window]   Fig. 7. Regional homologies among diverse arthropod body plans. The proposed relationships between insects, myriapods, anostracans and malacostracan crustaceans are based on patterns of Hox gene expression, indicated by colours: Antp, Ubx and AbdA in yellow; AbdB in red; Cad in purple (Averof and Akam, 1995; Abzhanov and Kaufman, 2000a; Abzhanov and Kaufman, 2000b; Hughes and Kaufman, 2002c). The post-genital region appears to be a unique region arising between the AbdB- and Cad-expressing domains in anostracan crustaceans, with no obvious counterpart in insects, myriapods and malacostracan crustaceans. The proposed relationships with body regions of cephalocarids and copepods are hypothetical (broken lines), based on similarities in the overall patterns of tagmosis and segmental specialisation among these groups (Averof and Akam, 1995; Walossek and Muller, 1997).