Differential gene expression analysis reveals functional roles of cryptic orange-pigmented organ in the colorless head kidney of Antarctic icefishes
Yoon, Eun Hye
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https://hdl.handle.net/2142/105079
Description
Title
Differential gene expression analysis reveals functional roles of cryptic orange-pigmented organ in the colorless head kidney of Antarctic icefishes
Author(s)
Yoon, Eun Hye
Issue Date
2019-04-24
Director of Research (if dissertation) or Advisor (if thesis)
Cheng, Chi-Hing C.
Committee Member(s)
DeVries, Arthur
Catchen, Julian
Department of Study
Animal Biology
Discipline
Ecology, Ethology, and Evolution
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Antarctic icefish
Head kidney
Interrenal tissue
Proline biosynthesis
RNA-Seq
Transcriptome
Abstract
We discovered an orange-pigmented, discrete body several millimeters in size embedded within the anterior end of the colorless head kidney of the hemoglobinless Antarctic icefishes. No macroscopically visible discrete organ has previously been reported in Antarctic fishes or teleost fishes in general. To assess the tissue type and functions of this cryptic orange body, we performed RNA sequencing and analyzed the orange body transcriptome relative to the surrounding head kidney tissue. We found 5,263 differentially expressed genes in the orange body, of which 4,624 genes were up-regulated and 639 down-regulated relative to the head kidney tissue. Differential gene expression analyses detected the enrichment of two main biological pathways: steroid hormone production and proline biosynthesis. The steroidogenic activities of the orange body indicate it performs functional roles of the interrenal tissue cells – the teleost homolog of the tetrapod adrenal cortex but are normally dispersed among the teleost head kidney tissue. Transcription of many cytochrome P450 enzymes participating in steroidogenesis were upregulated, potentially leading to greater levels of ROS and peroxidation of the lipid-rich steroid producing orange body cells. Proline is known to act as an antioxidant, thus, the detected enrichment in proline synthesis may be related to antioxidation defense mechanism, conferring protection against lipid peroxidation in steroid rich orange body cells.
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