Meagher Laboratory Why consider gene phylogenies?

1. Many plant organismal phylogenies have been dated relative to pollen and plant organ fossils. For example, the date at which monocots and dicots shared a common ancestor is approximately 200 to 250 million years ago (MYA).

2. When a dicot gene family member is much more similar to a monocot gene than to other members of that dicot gene family the simplest interpretation is that that gene predates the divergence between monocots and dicots.

3. This orthologous relationship of genes in distant species demonstrates that this gene type is particuarly well conserved relatively to other gene family members and that it has not been replaced by gene duplication for a significant amount of time. In the example, the gene type would have to be conserved for 200 million years.

4. Examples of gene family members studied in the Meagher laboratory that recently predate the monocot dicot split are most of the actins and the profilins. The late pollen actins are well characterized at more than 220 million years old.

5. Several of the plant ARP gene family members appear to predate the divergence of the eukaryotic kingdoms, which occured more than 1 billion years ago.

6. Any gene that has been conserved for more than 200 MY is undoubtely important to the survival of the plant.

7. Typical reasons that one gene family member might be so well conserved are: a) distinct patterns of organ, tissue, or temporal expression; b) distinct biochemical properties of the protein isovariant; c) distinct cell biological properties such as subcellular localization of the RNA or protein or d) isovariant dynamics.

Why compare gene trees and organismal phylogenies? Because this comparsison gives an estimate of the importance of a gene to plant survival and suggests its conserved specialized properties. The Meagher laboratory examined several gene families in detail as a prelude to it detailed molecular and cytogenetic analysis of the protein family.
	1. Many plant organismal phylogenies have been dated relative to pollen and plant organ fossils. For example, the date at which monocots and dicots shared a common ancestor is approximately 200 to 250 million years ago (MYA). 2. When a dicot gene family member is much more similar to a monocot gene than to other members of that dicot gene family the simplest interpretation is that that gene predates the divergence between monocots and dicots. 3. This orthologous relationship of genes in distant species demonstrates that this gene type is particuarly well conserved relatively to other gene family members and that it has not been replaced by gene duplication for a significant amount of time. In the example, the gene type would have to be conserved for 200 million years. 4. Examples of gene family members studied in the Meagher laboratory that recently predate the monocot dicot split are most of the actins and the profilins. The late pollen actins are well characterized at more than 220 million years old. 5. Several of the plant ARP gene family members appear to predate the divergence of the eukaryotic kingdoms, which occured more than 1 billion years ago. 6. Any gene that has been conserved for more than 200 MY is undoubtely important to the survival of the plant. 7. Typical reasons that one gene family member might be so well conserved are: a) distinct patterns of organ, tissue, or temporal expression; b) distinct biochemical properties of the protein isovariant; c) distinct cell biological properties such as subcellular localization of the RNA or protein or d) isovariant dynamics.