Saturday, December 3, 2016

[Paleontology • 2016] Molecular Evidence of Keratin and Melanosomes in Feathers of the Early Cretaceous Bird Eoconfuciusornis


The fossilized remains of Eoconfuciusornis, a beaked bird with no teeth, still contains traces of its original color.

Image: Xiaoli Wang.  DOI: 10.1073/pnas.1617168113  

 Significance
We report fossil evidence of feather structural protein (beta-keratin) from a 130-My-old basal bird (Eoconfuciusornis) from the famous Early Cretaceous Jehol Biota, which has produced many feathered dinosaurs, early birds, and mammals. Multiple independent molecular analyses of both microbodies and associated matrix recovered from the fossil feathers confirm that these microbodies are indeed melanosomes. We use transmission electron microscopy and immunogold to show localized binding of antibodies raised against feather protein to matrix filaments within these ancient feathers. Our work sheds new light on molecular constituents of tissues preserved in fossils.

Abstract
Microbodies associated with feathers of both nonavian dinosaurs and early birds were first identified as bacteria but have been reinterpreted as melanosomes. Whereas melanosomes in modern feathers are always surrounded by and embedded in keratin, melanosomes embedded in keratin in fossils has not been demonstrated. Here we provide multiple independent molecular analyses of both microbodies and the associated matrix recovered from feathers of a new specimen of the basal bird Eoconfuciusornis from the Early Cretaceous Jehol Biota of China. Our work represents the oldest ultrastructural and immunological recognition of avian beta-keratin from an Early Cretaceous (∼130-Ma) bird. We apply immunogold to identify protein epitopes at high resolution, by localizing antibody–antigen complexes to specific fossil ultrastructures. Retention of original keratinous proteins in the matrix surrounding electron-opaque microbodies supports their assignment as melanosomes and adds to the criteria employable to distinguish melanosomes from microbial bodies. Our work sheds new light on molecular preservation within normally labile tissues preserved in fossils.

Keywords: keratinous protein, immunogold, ChemiSTEM, melanosome, Early Cretaceous




Yanhong Pan, Wenxia Zheng, Alison E. Moyer, Jingmai K. O’Connor, Min Wang, Xiaoting Zheng, Xiaoli Wang, Elena R. Schroeter, Zhonghe Zhou and Mary H. Schweitzer. 2016. Molecular Evidence of Keratin and Melanosomes in Feathers of the Early Cretaceous Bird Eoconfuciusornis. PNAS. DOI: 10.1073/pnas.1617168113  

Keratin and melanosomes preserved in 130-million-year-old bird fossil http://phy.so/398952999 via @physorg_com
Feathers on This 130-Million-Year-Old Fossil Still Contain Traces of Color http://gizmodo.com/feathers-on-this-130-million-year-old-fossil-still-cont-1789217974


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