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Published online: 17 September 2008 | doi:10.1038/nchina.2008.218

Hydrobiology: Out of air, but not out of action

Jane Qiu

Introduction

© (2008) istockphoto.com/Angel Rodriguez

Haem oxygenases are key enzymes that catalyse the breakdown of haem proteins — the oxygen carriers in blood. To cope with the effects of low oxygen levels (hypoxia) in water, many fish species have evolved the genetic adaptation of increasing haem oxygenases in the body. Jianfang Gui and co-workers at the Chinese Academy of Sciences in Wuhan¹ have cloned and characterized an isoform of haem oxygenase-1 (CaHO-1) from hypoxia-tolerant goldfish.

The researchers found that CaHO-1 was mainly expressed in the posterior kidney, head kidney, gill and intestine; at the cellular level, CaHO-1 was localized in the cytoplasm and on the cell membrane. Under hypoxic stress, there was an increased expression of CaHO-1 in the posterior kidney in larvae, adults and cultured embryonic cells derived from the goldfish.

Interestingly, most of the cultured embryonic cells with artificial elevation of CaHO-1 expression were able to survive for four days in the presence of 1% oxygen, whereas a large percentage of their control counterparts died. When the normal oxygen level was restored, cells with elevated CaHO-1 expression proliferated at a faster rate than the controls.

Therefore, CaHO-1 might be a potential oxygen sensor and have an important protective role for the cells in response to hypoxic stress. Gui and co-workers consider that the diversity of fish species and their habitats might result in an extensive range of molecular adaptations to hypoxia.

The authors of this work are from:
State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China; Graduate University of the Chinese Academy of Sciences, Wuhan, China.

Reference

1. Wang, D., Zhong, X. P., Qiao Z. X. & Gui, J. F. Inductive transcription and protective role of fish heme oxygenase-1 under hypoxic stress. J. Exp. Biol. 211, 2700–2706 (2008).
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