Plant & Animal Genomes XIV Conference

January 14-18, 2006
Town & Country Convention Center
San Diego, CA

Control Of Flowering In Grasses – Aiming For Gene Containment

Christian S. Jensen^1,2 , Klaus Petersen² , Jerome Martin² , Gitte G. Larsen² , Ingo Lenk^1,2 , Thomas Didion² , Marianne Folling¹ , Caixia Gao¹ , Klaus K. Nielsen^1,2

¹  DLF-TRIFOLIUM A/S, Research Division, 31 Hoejerupvej, P.O Box 19, DK-4660 Store Heddinge, Demnar

²  Biosystems Department, RISOE National Laboratory, Box 49, DK-4000 Roskilde, Denmark

Genetic control of flowering is a fundamental, but complex process involving activation and repression of numerous genes engaged in different pathways. Development of containment strategies that will minimize transgene flow from GM-varieties to native grass species is a major focus area of the DLF-TRIFOLIUM grass research activities, other important goals being regulation of sugar metabolism, biotic- and abiotic stress tolerance, and altered cell wall composition. Technologies for prevention of flowering in grasses are based on constitutive expression of floral repressors, of which the Lolium perenne homologue of Terminal Flower1 was previously described. Another well-known floral repressor is the MADS-box encoding Flowering Locus C (FLC) gene from Arabidopsis, which is progressively downregulated by vernalization. No FLC homologs have been found outside the Brassicaceae, but through yeast two-hybrid screening we have identified three Lolium MADS box genes (LpMADS10, 14, 16) displaying expression patterns similar to FLC during vernalization. LpMADS10 interacts with LpMADS1, which is upregulated by vernalization and long days and may function as a floral inducer in grasses. Data from overexpression of LpMADS10 in Lolium perenne will be presented. Strategies for restoration of flowering include expression of floral inducers, such as CONSTANS, Flowering Locus T (FT), and APETALA1. Sequence homologs of these genes have been identified and functionally characterized in Arabidopsis. Surprisingly, expression of Lolium perenne FT-like (LpFT) did not lead to early flowering but instead caused a dramatic extension of the early vegetative phase. This result has implications for the current distinction between TFL1- and FT-like proteins as floral repressors and inducers, respectively.