RESEACH-PGR: Genomics of the Perennial/Annual Dichotomy in the Grass Tribe Triticeae

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The ability to regrow new tillers from the crown after a cycle of sexual reproduction is the hallmark of perennial bunchgrasses. In contrast, the entire plant senesces after a single sexual reproductive cycle and the next generation is established from seeds in annual grasses. Since the cultivation of annual grasses, such as wheat, barley, oats, rice, and maize, requires tilling of soil each season, which has numerous detrimental effects on the environment including release of heat-trapping gases into the atmosphere, it would be desirable to replace annual cereals with perennial forms in applications in which it makes economic sense. Based on this rationale, the goal of this project is to discover genes controlling the perennial growth in tall wheatgrass (Lophopyrum elongatum), which is closely related to wheat and can be used to create hybrid wheat-wheatgrass plants. To make this study possible, the tall wheatgrass genome will be sequenced. Expression of genes present in the genome of tall wheatgrass will then be compared with that of wheat during one reproductive cycle to identify genes controlling perennial growth. Finally, gene expression in genetic stocks where each tall wheatgrass chromosome has been individually incorporated into the wheat genome will be analyzed to identify genes playing the central role in bringing about perennial growth in tall wheatgrass. All project outcomes will be freely and publicly accessible through various websites and long term repositories. The knowledge and materials developed in this project will be used in the future to isolate these genes and to deploy them in breeding perennial forms of wheat and other cereals, in order to reduce the impact of agriculture on climate.Post-sexual cycle regrowth (PSCR) is a developmental marker for the polycarpic life history (PLH) in the perennial wheatgrasses of the genus Lophopyrum (tribe Triticeae, Poaceae) that show a caespitose or dense clumped/tufted growth habit. PSCR is absent from wheat, an annual with a monocarpic life history (MLH). The goal of this project is to discover key genes for perennial growth by analyzing gene expression in an octoploid amphiploid from the cross hexaploid (2n=42) bread wheat cv. Chinese Spring (CS) × diploid (2n=14) L. elongatum and in wheat. Each L. elongatum chromosome was individually added to the CS genome and each L. elongatum chromosome was individually substituted for its CS homoeologues. The L. elongatum genome present in the octoploid amphiploid will be sequenced and genes will be annotated. Gene expression will be compared with that in CS across one reproductive cycle including PSCR. Gene expression in the disomic substitution lines will be compared to identify genes with critical role for the expression of PSCR in the L. elongatum genome. Materials developed from prior NSF support will be used in exploratory research aiming at broadening the societal impact of this project. Since the cultivation of annual grasses is accompanied by undesirable ecological consequences, including poor carbon sequestration in soil and release of heat-trapping gases into the atmosphere, the developed knowledge will be practically important for future breeding of perennial forms of annual wheat, oats, and other cereals.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.