Progress 09/15/01 to 09/14/04
Outputs
During the funding period, we aim to dissect the mechanism of how SEUSS (SEU) and LEUNIG (LUG), two Arabidopsis transcription co-repressors, repress the expression of an important floral regulator AGAMOUS (AG) during flower development. we tested the repressor activities of LUG and SEU and showed that SEU and LUG directly interact with each other. Further, we identified APETALA1 (AP1) and SEPALLATA3 (SEP3) as the DNA-binding partners of LUG/SEU co-repressor complex. These research results led to a new model on how these repressors work to repress AG regulate flower development. The previous research model held that AG was turned on by default in all four floral whorls but was turned off in the outer two floral whorls by SEU and LUG. Our new model suggests that the SEU and LUG repressors turn off AG in all four whorls. But this turning-off is antagonized by several activating factors existing in the inner two whorls, allowing the expression of AG in the inner two whorls
and leading to the placement of stamens and pistils in the center of a flower.
Impacts
The research provides important mechanistic insights into how repressor genes function in plants. Such knowledge will be useful for future genetic engineering aimed at specifically switching on or off genes in order to improve crop traits. The result also illustrates how plant reproductive organs develop according to the activities of one or a few key regulatory genes. This will enable future genetic manipulation of reproductive organ formation. Since most fruits, nuts, and vegetables (such as tomato, squash) develop from the pistil of a flower, the ability to regulate the spatial and temporal activities of the class C gene may enable one to increase fruit number and size. Further, as pistils are bearers of seeds, the ability to regulate pistil development may enhance grain yield and seed production. In addition, the class C gene may serve as the target for gene repression and gene silencing leading to sterile flowers ideally suited for preventing transgene flow in the
wild. Finally, regulatory sequences that normally direct the expression of the class C gene may be used to drive the expression of foreign genes such as vaccines in fruits, leading to value-added new crops. During the funding period, one postdoctoral fellow and several undergraduate students were trained.
Publications
- (1) Bao, X., Franks, R.G., Levin, J.Z., and Liu, Z. (2004) Repression of AGAMOUS by BELLRINGR, in Floral and Inflorescence Meristems. Plant Cell 16, 1478-1489.
- (2) Sridhar, V.V., Surendrarao, A. Gonzalez, D., Conlan, C., Liu, Z. (2004) Transcriptional repression of target genes by LEUNIG and SEUSS, two interacting regulatory proteins for Arabidopsis flower development. Proc Natl Acad Sci U S A. 101, 11494-11499.
- (3) Liu, Z. (2005) Regulatory mechanisms for floral organ identity specification in higher plants. In Gene Expression and Regulation, a Current Scientific Frontiers Book (Ed. J. Ma), Springer Publishing.
- (4) Sridhar, V.V., Surendrarao, A., and Liu, Z (2006) APETALA1 and SEPALLATA3 interact with SEUSS to mediate transcription repression during flower development. Development 133, 3159-3166.
|