Dr. Annkatrin Rose

The evolutionary origin of the thylakoid protein MFP1 coincides with a terrestrial plant life style

Annkatrin Rose
Appalachian State University, Boone, NC 28608, USA

Chloroplast proteins fall into two categories based on their evolutionary origin: proteins of prokaryotic origin present in the ancestor of modern chloroplasts, and proteins of eukaryotic origin introduced from the host cell during chloroplast evolution. Sequence analysis of the thylakoid coiled-coil protein MFP1 suggests that it falls into the latter category. Homologs of Arabidopsis MFP1 can be identified in a wide range of angiosperms, all gymnosperm phyla, as well as seedless plants including ferns, a lycophyte and a bryophyte. To find more distantly related sequences, EST data and gene predictions were combined to identify a putative MFP1-like sequence from the terrestrial alga Klebsormidium flaccidum. Gene prediction on the Klebsormidium genomic sequence surrounding the match revealed a putative gene coding for a protein strongly resembling the domain structure of MFP1 but lacking significant sequence similarity to higher plant sequences. No sequences with significant similarities to this putative algal MFP1-like protein could be identified from other algae, such as Chlamydomonas, or cyanobacteria. Therefore, it appears to represent a novel protein in the streptophyte lineage. The presence of a putative MFP1-ancestor sequence in Klebsormidium, but not other fully sequenced algae genomes, proposes that the acquisition of this early form of MFP1 coincided with the transition from an aquatic to a terrestrial life style and suggests an adaptive function for the presence of a membrane-bound coiled-coil protein in chloroplasts for growth on land. Subsequently, this early MFP1-like protein underwent stabilizing selection for a TAT pathway thylakoid targeting signal during the transition from seedless vascular plants to seed plants.

Chalk Talk at the 30th Annual Plant Molecular Biology Retreat in Wrightsville Beach, NC, September 23-25, 2016.