High resolution mapping of the scs(ti) gene in durum wheat and conserved colinearity across three grass genomes: Wheat, rice and Brachypodium

In eukaryotic organisms, nuclear and cytoplasmic genomes interact to drive cellular functions. These genomes have co-evolved to form a functional relationship. Genes controlling nuclear-cytoplasmic compatibility affect interspecific and intergeneric crossability and viability of the hybrid zygote or seed and are likely involved in the origin and evolution of polyploid Triticeae. The Triticum turgidum L. var durum (2n = 4x = 28) nucleus is incompatible with the T. longissimum (2n = 2x = 14) cytoplasm. The Species Cytoplasm Specific (scs) and Vitality (Vi) genes are responsible for compatibility inducing action. This study was directed towards developing a detailed saturated map of a 3cM segment surrounding scsti ( scs derived from T. timopheevii Zhuk.) located on wheat chromosome 1A in a large euplasmic (true cytoplasm) population (4316 gametes). Using excellent synteny between wheat homeologous genomes and rice, we successfully developed molecular markers flanking 1.1cM of scs ti gene.Many important genes in grasses have been mapped and cloned using grass synteny, and among grasses, rice, being one of the smallest and completely sequenced genome, has contributed the most towards these studies. The successful high resolution mapping of scsti gene using physical map of wheat D genome and rice chromosome 10 lead to another main objective of this study: to investigate microcolinearity between physical maps of wheat D genome and rice investigate microcolinearity between physical maps of wheat D genome and rice chromosome 10. Nine of the 70 wheat tentative consensus sequences showed homology between the two genomes along with microcolinearity frequently disrupted by rearrangements. Additionally, we investigated the relationship between rice chromosome 10 and new model grass species Brachypodium. The Brachypodium distachyon BAC end sequences from contig 89 were compared with rice, and the results revealed excellent colinearity between the two models for the region of interest. Thus Brachypodium along with rice can successfully be used for inter and intraspecific mapping of grasses.