Abstract Detail

Development and Structure

Sengupta, Aniket [1], Howarth, Dianella [2].

Gain and loss of domains in the origin of DIV and RAD genes.

DIVARICATA-like or DIV genes, as exemplified by the Antirrhinum majus DIV gene (AmDIV), have two MYB domains: MYB-1 and MYB-2 domains. They additionally have a 13 amino acid long conserved region (KDKRRASIHDITT) downstream of the MYB2 domain (the “HDI” domain). So, the DIV genes in Green Plants have the following domain organization: MYB-1—MYB-2—HDI. We demonstrate that the ancestral DIV gene in vascular plants underwent two duplications, resulting in three clades of DIV in vascular plants. One of these clades acquired an early stop codon in the seed plants and lost the MYB2 and HDI domains. This truncated gene became the RADIALIS-like gene or RAD (that has only the MYB-1 domain). Since RAD genes evolved in seed plants, we test the expression of RAD and DIV genes in the gymnosperm Ginkgo biloba. RAD genes are modified DIV genes but where did DIV genes come from? Interestingly, the DIV genes in Glaucophyta (which is an early diverging Archaeplastida) and in Cryptomonads (which are sister to Archaeplastida), have a third MYB domain (henceforth “MYB-A” domain) upstream of the MYB-1 domain. That is, these early DIV genes have the following organization: MYB-A—MYB-1—MYB-2—HDI. We show that the DIV genes likely evolved by the combination of two separate genes present in many eukaryotes outside Plantae. The first contributor had a MYB-A—MYB-1 organization and the second had a MYB2—HDI organization. The MYB-A domain was later lost in Green Plants, leading to the typical MYB-1—MYB-2—HDI organization seen in AmDIV. Deeper nodes in the species-tree of eukaryotes are not well resolved, and there have been recurrent horizontal gene transfer among eukaryotes (including during endosymbiosis of Red and Green Algae by other eukaryotes). Depending on how the earliest nodes in the tree of eukaryotes are resolved, the DIV genes are either ancestral to a sub-group of eukaryotes that include Archaeplastida and Cryptomonads, or to a larger group of organisms that also include Stramenopiles, Alveolates, and Rhizaria. DIV genes, that are well characterized in their function in flowers, are not unique to angiosperms or even to plants. Their origin lies close to the diversification of eukaryotes.

1 - St. John's University, Biological Sciences, 8000 Utopia Parkway, Albert Hall Room 257, Jamaica, NY, 11366, United States
2 - St. John's University, Department Of Biological Sciences, St. Albert Hall Rm 257, 8000 Utopia Pkwy, Jamiaca, NY, 11439, United States

Keywords:
DIVARICATA
RADIALIS
MYB genes
Algae
Duplication.

Presentation Type: Oral Paper
Number: DS5002
Abstract ID:554
Candidate for Awards:None