Fine Mapping of a Degenerated Abdominal Legs Mutant (Edl) in Silkworm, Bombyx mori

PLOS ONE, Dec 2019

In insects, abdominal appendages, also called prolegs, vary due to adaptive evolution. Mutations on prolegs within species provide insights to better understand the mechanisms underlying appendage development and diversity. In silkworm Bombyx mori, extra-crescents and degenerated abdominal legs (Edl) mutant, belonging to the E pseudoallele group, is a spontaneous mutation that adds crescents and degenerates prolegs on the third abdominal segment (A3). This mutation may be a homeotic transformation of A3 to A2. In this study, the Edl locus was mapped within approximately a 211 Kb region that is 10 Kb upstream of Bmabdominal-A (Bmabd-A). RT-quantitative PCR (RT-qPCR) and Western blot analysis of Bmabd-A expression showed a slight but significant decrease, while the expression of BmUltrabithorax (BmUbx) was up-regulated in the Edl mutant compared to wildtype (Dazao). Moreover, we also found that BmDistal-less (BmDll), which regulated the development of distal proleg structures, was missing at the tips of the A3 prolegs in the Edl mutant compared to BmDll expression in normally developed prolegs in both the wildtype and mutant. Collectively, we identified approximately a 211 Kb region in the Edl locus that regulates BmUbx and Bmabd-A expression and found that changes in BmUbx and Bmabd-A expression may lead to the loss of distal proleg structures in B. mori.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0169224&type=printable

Fine Mapping of a Degenerated Abdominal Legs Mutant (Edl) in Silkworm, Bombyx mori

January Fine Mapping of a Degenerated Abdominal Legs Mutant (Edl) in Silkworm, Bombyx mori Honglei Wang☯ 0 1 2 Xiaoling Tong☯ 0 1 2 Meijing Liu 0 1 2 Hai Hu 0 1 2 Zhiquan Li 0 1 2 Zhonghuai Xiang 0 1 2 Fangyin Dai 0 1 2 Cheng Lu 0 1 2 ☯ These authors contributed equally to this work. 0 1 2 0 1 2 0 1 2 0 State Key Laboratory of Silkworm Genome Biology, Key Laboratory for Sericulture Functional Genomics and Biotechnology of Agricultural Ministry, Southwest University , Chongqing , China 1 Research and Development 863 Program of China Grant (No. 2013AA102507) , National Natural Science Foundation of China (No. 31472153, No. 30901053 and No. 31372379) , Fundamental Research Funds for the Central Universities in 2 Editor: Erjun Ling, Institute of Plant Physiology and Ecology Shanghai Institutes for Biological Sciences , CHINA In insects, abdominal appendages, also called prolegs, vary due to adaptive evolution. Mutations on prolegs within species provide insights to better understand the mechanisms underlying appendage development and diversity. In silkworm Bombyx mori, extra-crescents and degenerated abdominal legs (Edl) mutant, belonging to the E pseudoallele group, is a spontaneous mutation that adds crescents and degenerates prolegs on the third abdominal segment (A3). This mutation may be a homeotic transformation of A3 to A2. In this study, the Edl locus was mapped within approximately a 211 Kb region that is 10 Kb upstream of Bmabdominal-A (Bmabd-A). RT-quantitative PCR (RT-qPCR) and Western blot analysis of Bmabd-A expression showed a slight but significant decrease, while the expression of BmUltrabithorax (BmUbx) was up-regulated in the Edl mutant compared to wildtype (Dazao). Moreover, we also found that BmDistal-less (BmDll), which regulated the development of distal proleg structures, was missing at the tips of the A3 prolegs in the Edl mutant compared to BmDll expression in normally developed prolegs in both the wildtype and mutant. Collectively, we identified approximately a 211 Kb region in the Edl locus that regulates BmUbx and Bmabd-A expression and found that changes in BmUbx and BmabdA expression may lead to the loss of distal proleg structures in B. mori. - Copyright: © 2017 Wang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: Most relevant data are within the paper and its Supporting Information files, and other relevant data are available from the NCBI database (accession numbers KX344456KX344459). Introduction Morphological characteristics of insects are surprisingly variable. Particularly, the appendage number, morphology and position vary largely within and between species. Studies on the mechanisms underlying appendage development and diversity provide insights into the evolutionary process of arthropods [1±3]. Each thoracic segment, on the ventral side of an insects' trunk, contains appendages called thoracic legs. The appendages on the abdominal segments are known as prolegs and their numbers vary markedly [ 4 ]. Segmental identities of these legs are determined by several Homeotic genes [ 5 ], which consist of a tandem gene cluster where the order of genes is co-linear with their expression pattern on the body axis [ 6 ]. The development of prolegs is mainly China (No. XDJK2013A001), and Chongqing Youth Science and Technology Talent Training Project (cstc2014kjrc-qnrc80001). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. regulated by Ultrabithorax (Ubx) and abdominal-A (abd-A). For example, in the dipteran, Drosophila melanogaster, abdominal-B (abd-B), abd-A and Ubx repress proleg development [7±9]; in the flour beetle, Tribolium castaneum, Ubx does not repress but modifies the morphology of prolegs on abdomen 1 (A1), abd-A represses the development of proleg on the posterior abdominal segments [ 10 ]; in the lepidopteran, Manduca sexta, Ubx represses the development of prolegs on the anterior abdomen, but abd-A does not repress the development of prolegs because robust expression of abd-A is found in proleg primordia of A3-A6, which develop into prolegs [ 11 ]. Finally, in the lepidopteran, Bombyx mori, BmUbx and Bmabd-B repress the development of prolegs on the anterior and posterior abdominal segments, respectively; Bmabd-A, on the other hand, is known to play an important role in the development of prolegs on the intermediate abdominal segments, and RNAi of Bmabd-A results in the deletion of prolegs [12±17]. Studies in Drosophila have shown that the bithorax complex (BX-C) contains many cis-regulatory elements and some non-protein coding transcripts, which work together to control neighboring Hox gene expression [18±20]. The cis-regulatory elements are organized (...truncated)


This is a preview of a remote PDF: https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0169224&type=printable

Honglei Wang, Xiaoling Tong, Meijing Liu, Hai Hu, Zhiquan Li, Zhonghuai Xiang, Fangyin Dai, Cheng Lu. Fine Mapping of a Degenerated Abdominal Legs Mutant (Edl) in Silkworm, Bombyx mori, PLOS ONE, 2017, Volume 12, Issue 1, DOI: 10.1371/journal.pone.0169224