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Title: Silk gland gene expression during larval-pupal transitionin the cotton leaf roller Sylepta derogate (Lepidoptera: pyralidae)

Author
item SU, HONGHUA - Yangzhou University
item CHENG, YUMING - Yangzhou University
item WANG, ZHONGYANG - Yangzhou University
item LI, ZHONG - Yangzhou University
item Stanley, David
item YANG, YIZHONG - Yangzhou University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2015
Publication Date: 9/9/2015
Citation: Su, H., Cheng, Y., Wang, Z., Li, Z., Stanley, D.W., Yang, Y. 2015. Silk gland gene expression during larval-pupal transitionin the cotton leaf roller Sylepta derogate (Lepidoptera: pyralidae). PLoS One. DOI: 10.1371/PONE.2015-0136868.

Interpretive Summary: Application of classical insecticides has introduced severe problems in agricultural sustainability and new pest control technologies are necessary. One new approach is developing tools to silence genes that are critical in the life history of pest insects. An important part of this new technology is selecting the most appropriate genes for silencing. Because silk production is crucial to the lives of some pest insects, silencing a key gene in silk production may be an effective pest control technology. In this paper we investigated gene expression in silk glands of a pest insect. We identified several genes that undergo very large changes in expression during the larva to pupa transition. These genes may be appropriate targets for silencing. This new research will be directly useful to scientists who are working to generate new insect pest control technologies. The ensuing improved pest management tools will benefit a wide range of agricultural producers by supporting the long-term sustainability of agriculture.

Technical Abstract: The cotton leaf roller, Sylepta derogata, is a silk-producing insect pest. While young larvae feed on the underside of leaves, the older ones roll cotton leaves and feed on the leaf edges, which defoliates cotton plants. The larvae produce silk to stabilize the rolled leaf and to balloon from used to new leaves. Despite the significance of silk in the biology of pest insect species, there is virtually no information on the genes involved in forming their silk. This is a substantial knowledge gap because some of these genes may be valuable targets for developing molecular pest management technologies. We addressed the gap by posing the hypothesis that silk gland gene expression changes during the transition from larvae to pupae. We tested our hypothesis using RNA-seq to investigate changes in silk gland gene expression at three developmental stages, 5th instar larval (silk producing; 15,445,926 clean reads), prepupal (reduced silk producing; 13,758,154) and pupal (beyond silk producing; 16,787,792). We recorded 60,298 unigenes and mapped 50,158, 48,415 and 46,623 of them to the NCBI database. Most differentially expressed genes in the 5th instar larvae/prepupae libraries were relevant to nucleotide synthesis and maintenance of silk gland function. We identified down-regulated transcriptional factors and several genes involved in silk formation in the three libraries and verified the expression pattern of eight genes by qPCR. The developmental- and tissue-specific expression patterns of the fibroin light chain gene showed it was highly expressed during the larval silk-producing stage and its expression in the larval silk gland was far higher compared to other tissues, including midgut, hindgut, epidermis, Malpighian tubes, hemolymph and fat body. These new data will guide the selection of key genes that may be targeted for in planta gene-silencing technologies for sustainable cotton agriculture.