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Title: ULTRAPETALA trxG genes interact with KANADI transcription factor genes to regulate Aradopsis Gynoecium patterning

item PIRES, HELENA - University Of California
item MONFARED, MONA - University Of California
item SHEMYAKINA, ELANA - University Of California
item Fletcher, Jennifer

Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2014
Publication Date: 11/1/2014
Citation: Pires, H.R., Monfared, M.M., Shemyakina, E.A., Fletcher, J.C. 2014. ULTRAPETALA trxG genes interact with KANADI transcription factor genes to regulate Aradopsis Gynoecium patterning. The Plant Cell. 26:4345-4361.

Interpretive Summary: The fruit of thale cress, Arabidopsis thaliana, forms in the center of the developing flower and encloses the seeds of the next generation of the plant. In order to correctly form the fruit organ, called the gynoecium, the top (apical) end must have a different structure from the bottom (basal) end and the inside (adaxial) from the outside (abaxial). This work investigates how two genes, called ULTRAPETALA1 (ULT1) and KANADI1 (KAN1), function to control the development of these different parts of the fruit. Our study shows that ULT1 gene and the KAN1 gene act oppositely to direct adaxial-abaxial axis formation in the developing fruit, whereas they work together with the ULT2 and KAN2 genes to direct apical-basal axis formation by informing the cells at the bottom of the fruit that they should form the base. Because many crop plant species produce fruits that are important for human consumption (eg. tomato, citrus, stone fruits, etc), our research may enhance efforts to improve fruit yield for agriculture.

Technical Abstract: Organ formation relies upon precise patterns of gene expression that are under tight spatial and temporal regulation. Transcription patterns are specified by several cellular processes during development, including chromatin remodeling, but little is known about how chromatin remodeling factors contribute to plant organogenesis. We demonstrate that the trithorax group (trxG) gene ULTRAPETALA1 (ULT1) and the GARP transcription factor gene KANADI1 (KAN1) organize the Arabidopsis gynoecium along two distinct polarity axes. We show that ULT1 activity is required for the kan1 adaxialized polarity defect, indicating that ULT1 and KAN1 act oppositely to regulate the adaxial-abaxial axis. Conversely, ULT1 and KAN1 together establish apical-basal polarity by promoting basal cell fate in the gynoecium, restricting the expression domain of the bHLH transcription factor gene SPATULA (SPT). Finally, we show that ult alleles display dose-dependent genetic interactions with kan alleles, and that ULT and KAN proteins can physically associate. Our findings identify a novel dual role for plant trxG factors in organ patterning, with ULT1 and KAN1 acting antagonistically to pattern the adaxial-abaxial polarity axis but jointly to pattern the apical-basal axis. Our data indicate that the ULT proteins function to link chromatin remodeling factors with DNA-binding transcription factors to regulate target gene expression.