| Autor: |
Shimeld, Sebastian M., Purkiss, Andrew G., Dirks, R.P.H., Bateman, Orval A., Slingsby, Christine, Lubsen, N.H. |
| Jazyk: |
angličtina |
| Rok vydání: |
2005 |
| Předmět: |
|
| ISSN: |
0960-9822 |
| Popis: |
A refracting lens is a key component of our image-forming camera eye; however, its evolutionary origin is unknown because precursor structures appear absent in nonvertebrates [1]. The vertebrate beta gamma-crystallin genes encode abundant structural proteins critical for the function of the lens [2]. We show that the urochordate Ciona intestinalis, which split from the vertebrate lineage before the evolution of the lens, has a single gene coding for a single domain monomeric beta gamma-crystallin. The crystal structure of Ciona beta gamma-crystallin is very similar to that of a vertebrate beta gamma-crystallin domain, except for paired, occupied calcium binding sites. The Ciona beta gamma-crystallin is only expressed in the palps and in the otolith, the pigmented sister cell of the light-sensing ocellus. The Ciona beta gamma-crystallin promoter region targeted expression to the visual system, including lens, in transgenic Xenopus tadpoles. We conclude that the vertebrate beta gamma-crystallins evolved from a single domain protein already expressed in the neuroectoderm of the prevertebrate ancestor. The conservation of the regulatory hierarchy controlling beta gamma-crystallin expression between organisms with and without a lens shows that the evolutionary origin of the lens was based on co-option of pre-existing regulatory circuits controlling the expression of a key structural gene in a primitive light-sensing system. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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