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Analysis of four achaete-scute homologs in Bombyx mori reveals new viewpoints of the evolution and functions of this gene family.

Zhou Q, Zhang T, Xu W, Yu L, Yi Y, Zhang Z - BMC Genet. (2008)

Bottom Line: Functions besides neural development controlling have also been found in Drosophila AS-C genes.Proteins encoded by them contained the characteristic bHLH domain and the three proneural ones were also found to have the C-terminal conserved motif.AS-C gene duplication in insects occurs after or parallel to, but not before the taxonomic order formation during evolution.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Biotechnology Research Institute, National Engineering of crop germplasm and genetic improvement, Chinese Academy of Agricultural Sciences, Beijing, 100081, China. Qingxiang_Zhou@meei.harvard.edu

ABSTRACT

Background: achaete-scute complexe (AS-C) has been widely studied at genetic, developmental and evolutional levels. Genes of this family encode proteins containing a highly conserved bHLH domain, which take part in the regulation of the development of central nervous system and peripheral nervous system. Many AS-C homologs have been isolated from various vertebrates and invertebrates. Also, AS-C genes are duplicated during the evolution of Diptera. Functions besides neural development controlling have also been found in Drosophila AS-C genes.

Results: We cloned four achaete-scute homologs (ASH) from the lepidopteran model organism Bombyx mori, including three proneural genes and one neural precursor gene. Proteins encoded by them contained the characteristic bHLH domain and the three proneural ones were also found to have the C-terminal conserved motif. These genes regulated promoter activity through the Class A E-boxes in vitro. Though both Bm-ASH and Drosophila AS-C have four members, they are not in one by one corresponding relationships. Results of RT-PCR and real-time PCR showed that Bm-ASH genes were expressed in different larval tissues, and had well-regulated expressional profiles during the development of embryo and wing/wing disc.

Conclusion: There are four achaete-scute homologs in Bombyx mori, the second insect having four AS-C genes so far, and these genes have multiple functions in silkworm life cycle. AS-C gene duplication in insects occurs after or parallel to, but not before the taxonomic order formation during evolution.

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Tissue expression distribution of Bm-ASH genes in silkworm larvae. RT-PCR templates including: ectoderm tissues H (head), WD (wing disc), S-G (silk gland), MT (Malpighian tubule), TC (trachea cluster), BW (body wall); mesoderm tissues He (hemocyte), FB (fat body), G (gonad, T (testis), O (ovary)); and endoderm tissue MG (midgut). V3d stands for 3-day-old larvae of the 5th instar, and S stands for 8-day-old larvae of the 5th instar (begin spinning). Amplification cycles were 30 for Bm-ASH1, Bm-ASH2, Bm-ASH3 and Bm-ase, and 25 for the internal control gene Bm-actin A3.
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Figure 6: Tissue expression distribution of Bm-ASH genes in silkworm larvae. RT-PCR templates including: ectoderm tissues H (head), WD (wing disc), S-G (silk gland), MT (Malpighian tubule), TC (trachea cluster), BW (body wall); mesoderm tissues He (hemocyte), FB (fat body), G (gonad, T (testis), O (ovary)); and endoderm tissue MG (midgut). V3d stands for 3-day-old larvae of the 5th instar, and S stands for 8-day-old larvae of the 5th instar (begin spinning). Amplification cycles were 30 for Bm-ASH1, Bm-ASH2, Bm-ASH3 and Bm-ase, and 25 for the internal control gene Bm-actin A3.

Mentions: To understand the potential in vivo regulations of ASH genes, we detected the expression status of Bombyx ASH genes in different tissues of the 5th instar larvae on the 3rd and the 8th days (just after spinning) (Fig. 6). The data showed that Bm-ASH1 and Bm-ASH2 were expressed in organs derived from all the three cellular derms: ectoderm, mesoderm and endoderm; whereas Bm-ASH3 and Bm-ase were only expressed in tissues derived from ectoderm and mesoderm. Bm-ASH1 was expressed in all organs except silk glands (S-G) and hemocytes (He), and at a low level in 5 d and had no expression in 8 d fat body (FB). Bm-ASH2 was widely expressed in all the investigated samples. The expression of Bm-ASH3 and Bm-ase were more tissue specific, and the level of Bm-ase was relatively lower. Bm-ASH1 and Bm-ASH2 had high expression levels in gonads (G), while Bm-ASH2 and Bm-ASH3 had high expression levels in tracheal clusters (Tc). All of the data suggested that the four Bm-ASH genes might play various roles in the development of silkworm larva. We should note that all three proneural genes expressed highly in WD, and Bm-ase had a relatively higher expression level in 8 d WD. These implied that Bm-ASH genes might be important for the development of the wing disc.


Analysis of four achaete-scute homologs in Bombyx mori reveals new viewpoints of the evolution and functions of this gene family.

Zhou Q, Zhang T, Xu W, Yu L, Yi Y, Zhang Z - BMC Genet. (2008)

Tissue expression distribution of Bm-ASH genes in silkworm larvae. RT-PCR templates including: ectoderm tissues H (head), WD (wing disc), S-G (silk gland), MT (Malpighian tubule), TC (trachea cluster), BW (body wall); mesoderm tissues He (hemocyte), FB (fat body), G (gonad, T (testis), O (ovary)); and endoderm tissue MG (midgut). V3d stands for 3-day-old larvae of the 5th instar, and S stands for 8-day-old larvae of the 5th instar (begin spinning). Amplification cycles were 30 for Bm-ASH1, Bm-ASH2, Bm-ASH3 and Bm-ase, and 25 for the internal control gene Bm-actin A3.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2315653&req=5

Figure 6: Tissue expression distribution of Bm-ASH genes in silkworm larvae. RT-PCR templates including: ectoderm tissues H (head), WD (wing disc), S-G (silk gland), MT (Malpighian tubule), TC (trachea cluster), BW (body wall); mesoderm tissues He (hemocyte), FB (fat body), G (gonad, T (testis), O (ovary)); and endoderm tissue MG (midgut). V3d stands for 3-day-old larvae of the 5th instar, and S stands for 8-day-old larvae of the 5th instar (begin spinning). Amplification cycles were 30 for Bm-ASH1, Bm-ASH2, Bm-ASH3 and Bm-ase, and 25 for the internal control gene Bm-actin A3.
Mentions: To understand the potential in vivo regulations of ASH genes, we detected the expression status of Bombyx ASH genes in different tissues of the 5th instar larvae on the 3rd and the 8th days (just after spinning) (Fig. 6). The data showed that Bm-ASH1 and Bm-ASH2 were expressed in organs derived from all the three cellular derms: ectoderm, mesoderm and endoderm; whereas Bm-ASH3 and Bm-ase were only expressed in tissues derived from ectoderm and mesoderm. Bm-ASH1 was expressed in all organs except silk glands (S-G) and hemocytes (He), and at a low level in 5 d and had no expression in 8 d fat body (FB). Bm-ASH2 was widely expressed in all the investigated samples. The expression of Bm-ASH3 and Bm-ase were more tissue specific, and the level of Bm-ase was relatively lower. Bm-ASH1 and Bm-ASH2 had high expression levels in gonads (G), while Bm-ASH2 and Bm-ASH3 had high expression levels in tracheal clusters (Tc). All of the data suggested that the four Bm-ASH genes might play various roles in the development of silkworm larva. We should note that all three proneural genes expressed highly in WD, and Bm-ase had a relatively higher expression level in 8 d WD. These implied that Bm-ASH genes might be important for the development of the wing disc.

Bottom Line: Functions besides neural development controlling have also been found in Drosophila AS-C genes.Proteins encoded by them contained the characteristic bHLH domain and the three proneural ones were also found to have the C-terminal conserved motif.AS-C gene duplication in insects occurs after or parallel to, but not before the taxonomic order formation during evolution.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Biotechnology Research Institute, National Engineering of crop germplasm and genetic improvement, Chinese Academy of Agricultural Sciences, Beijing, 100081, China. Qingxiang_Zhou@meei.harvard.edu

ABSTRACT

Background: achaete-scute complexe (AS-C) has been widely studied at genetic, developmental and evolutional levels. Genes of this family encode proteins containing a highly conserved bHLH domain, which take part in the regulation of the development of central nervous system and peripheral nervous system. Many AS-C homologs have been isolated from various vertebrates and invertebrates. Also, AS-C genes are duplicated during the evolution of Diptera. Functions besides neural development controlling have also been found in Drosophila AS-C genes.

Results: We cloned four achaete-scute homologs (ASH) from the lepidopteran model organism Bombyx mori, including three proneural genes and one neural precursor gene. Proteins encoded by them contained the characteristic bHLH domain and the three proneural ones were also found to have the C-terminal conserved motif. These genes regulated promoter activity through the Class A E-boxes in vitro. Though both Bm-ASH and Drosophila AS-C have four members, they are not in one by one corresponding relationships. Results of RT-PCR and real-time PCR showed that Bm-ASH genes were expressed in different larval tissues, and had well-regulated expressional profiles during the development of embryo and wing/wing disc.

Conclusion: There are four achaete-scute homologs in Bombyx mori, the second insect having four AS-C genes so far, and these genes have multiple functions in silkworm life cycle. AS-C gene duplication in insects occurs after or parallel to, but not before the taxonomic order formation during evolution.

Show MeSH
Related in: MedlinePlus