Chromatin landscape changes and flower formation
Chromatin context (or the packing of DNA around histone proteins) regulates the reading through genetic material and therefore is a source of control of gene expression. Addressing the regulation of flower formation, researchers with the EU-funded CHROMACT (Chromatin dynamics for gene activation in the developing flower) project studied one actor in particular: ULTRAPETALA1 (ULT1). The transcriptional activator ULT1 is thought to be involved in several steps of chromatin-mediated activation of genes controlling flower formation. In particular it controls the setting of histone marks when histones are modified to direct or suppress transcription. To get a global view on ULT1 function in flower development, CHROMACT researchers performed a quantitative analysis of histone mark frequency at the genome-wide level. For this, they developed a protocol to generate high quality sequence reads of marked regions, along with an analysis pipeline for the output dataset. Results show that ULT1 antagonises the Polycomb group (PcG) function at a genome-wide level, to allow proper flower formation when appropriate. PcG proteins inhibit flowering, for example in winter when fruiting would not be possible with limited water and sunlight. The researchers also investigated the mode of ULT1 targeting to chromatin, and found a set of direct target genes bound along an active histone mark profile. Moreover, analysis of the DNA binding sequence motif of a transcription factor that interacts with ULT1 has given data for further investigations. Further work in collaboration with other labs – Wellmer group, Dublin; Kaufmann group, Potsdam; Carles group, Grenoble – shall allow studying the overall dynamics of chromatin landscapes in Arabidopsis. A first set of analyses revealed that quantitative changes in histone marks are widely correlated with the expected changes in expression of genes related to early events in flower formation. Research results have been submitted for publication. They constitute a strong knowledge platform for further research into the function of transcriptional regulators (binding, effect on histone marks) in link with chromatin dynamics. ULT1 is present in economically important crops such as tomato, maize and wheat. Study of the function of this protein in gene switches could be applicable in the realms of plant breeding and crop manipulation to increase yield.
Keywords
Chromatin, flower formation, crop, ULTRAPETALA1, histone, Polycomb group