This nature’s cover story “THE GREEN HOURGLASS” was really an exciting paper. I regret to not be able to fully capture it two years ago.
The authors adapted the embryonic hourclass model proposed from vertebrates (as the figure show below) to plants, and provided the transcriptomic evidence from two complementary analyses. What is the embryonic hourclass? It refers to embryos from various taxa appear different in early stages, and converge to a similar form during mid-embryogenesis (or called phylotypic stage), and again diverge in later stages.
Recent analyses using zebrafish and Drosophila demonstrated the transcriptome was dominated by ancient genes. Here in this paper, the authors calculated two different transcriptome indices: transcriptome age index (TAI) and transcriptome divergence index (TDI). The indices were computed across seven embryo stages. After visualization of the indices, clear hourclass patterns (see figure below from the paper) were found for both measurements.
What we can learn from this study are that (1) try to answer historical or classical biological questions with modern resources and (2) use open data to do it.
Quint, M., Drost, H.-G., Gabel, A., Ullrich, K. K., Bönn, M., & Grosse, I. (2012). A transcriptomic hourglass in plant embryogenesis. Nature, 490(7418), 98–101. doi:10.1038/nature11394
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