|BASSI, FILLIPO - International Center For Agricultural Research In The Dry Areas (ICARDA)
|GHAVAMI, FARHAD - University Of Minnesota
|HAYDEN, MATTHEW - La Trobe University
|WANG, YI - University Of California
|FORREST, KERRIE - La Trobe University
|KONG, STEPHAN - La Trobe University
|DIZON, RHODERISSA - North Dakota State University
|MICHALAK DE JIMENEZ, MONIKA - North Dakota State University
|MEINHARDT, STEVEN - North Dakota State University
|MERGOUM, MOHAMED - North Dakota State University
Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2016
Publication Date: 8/1/2016
Citation: Bassi, F.M., Ghavami, F., Hayden, M.J., Wang, Y., Forrest, K., Kong, S., Dizon, R.G., Michalak De Jimenez, M.K., Meinhardt, S., Mergoum, M., Gu, Y.Q., Kianian, S. 2016. A rhomboid gene controls speciation through regulation of nuclear-mitochondrial compatibility in Triticum. Plant Biotechnology Journal. 14(8):1716-26.
Interpretive Summary: We report the cloning of the species cytoplasm specific (scs) gene, which orchestrated the crosstalk between nucleus and mitochondria throughout the evolution of cereals. The cloning was achieved by a novel methodology involving next-generation sequencing and unique plant material. Mutants for the scs gene were characterized by electro scan microscopy to document the progression of vacuolar mediated programmed cell death in seeds of wheat. Most important, the predicted protein structure of scs revealed a possible explanation to the erratic mitochondria signaling occurring in the mutants. A similar erratic signaling is causative of major illnesses in humans such as type II diabetes, Alzheimer, and Parkinson. Application of the knowledge gathered here could provide solutions applicable beyond the plant kingdom.
Technical Abstract: The nuclear encoded species cytoplasm specific (scs) genes control nuclear-cytoplasmic compatibility in Triticum. Alloplasmic cells, which have nucleus and cytoplasm derived from different species, produce vigorous and vital organisms only when the correct version of scs is present in their nucleus. In this study, electron microscopic analysis revealed that pre-mature cell death results when an incompatible nucleus and cytoplasm are present in the embryo of Triticum. Fast-forward positional cloning through a combination of phenotyping radiation hybrid lines, genotyping by sequencing, and a novel in silico approach allowed rapid identification of a rhomboid gene as the scs locus. Three dimensional protein modeling provided mechanistic insight into the role of this gene in controlling nuclear-cytoplasmic compatibility. Gene expression characterization revealed that an active copy of this rhomboid locus exists on all homoeologus chromosomes of wheat, and depending on the specific cytoplasm each copy is preferentially expressed. The "Maan's scs hypothesis" stated that the cytoplasmic genome and scs genes are intimately involved in the differentiation of diploid species, development of interspecific genetic isolating mechanisms, and the origin of polyploid species in Triticum and related genera. The data provided here supports the involvement of the rhomboid protein in guiding the speciation of Triticum and possibly other cereals through the determination of nuclear and plasmon compatibility.