Much progress has been made in elucidating the mechanisms of transcriptional regulation in eukaryotes. It is becoming clear that the regulatory specificity of transcription factors (TFs) is not given only by their interaction with conserved DNA-sequence motifs in the promoters of the genes that they control, but also by the interactions with other factors, which may or may not bind the target promoters. This strategy, also known as combinatorial transcriptional control, has been best studied in plants in studies focusing on the regulation of flavonoid biosynthesis in maize. read more....

Understanding REDOX Regulation of Transcription Factor Activity

MYB domain proteins are conserved transcriptional regulators that are found in all eukaryotes. These transcriptional regulators include the widely distributed three MYB repeat proteins (R1R2R3) represented in animals by the c-MYB proto-oncogene and in plants by both the pc-MYB (R1R2R3) and the two MYB repeat proteins (R2R3), the latter of which has expanded dramatically in higher plants. Some residues within the MYB domain have remained conserved in all eukaryotes while others are conserved only in the higher plants R2R3 MYB proteins. Our studies have focused on Cys53, which is found in MYB domains from plants and animals and which must be reduced for DNA-binding and transcriptional activation. read more....

The Grass Regulatory Information Server (GRASSIUS, www.grassius.org) provides a resource similar to AGRIS (http://arabidopsis.med.ohio-state.edu/), integrating information on transcription factors (TFs), promoter and cis-regulatory element (CREs) across the grasses grasses (sugarcane, maize, rice, and sorghum), providing a valuable tool for comparative regulatory genomics.   GRASSIUS houses three databases, GRASSTFDB (Grass Transcription Factor Database), GRASSPROMDB (Grass Promoter Database) and GRASSREGNET (Grass Regulatory Network Database). GRASSPROMDB has promoter sequences in which predicted and experimentally verified cis-regulatory elements (CREs) are indicated. GRASSTFDB is a collection of TFs from maize, sugarcane, and rice. GRASSREGNET will integrate information housed in GRASSPROMDB and GRASSTFDB in the light of experimentally verified interactions in order to establish regulatory motifs across. read more....

 

Functional divergence of R2R3 Myb genes after duplication

R2R3 Myb genes constitute one of the largest families of regulatory proteins in plants. In the grasses, a group of these genes underwent amplification about 50 million years ago and is characterized by a change of proline to alanine in the hinge region between R2 and R3 and hence called as P-to-A clade. R2R3 Myb P-to-A genes comprise about 10 members, including well-characterized maize P1 regulator of phlobaphene biosynthesis. ZmMyb-IF35, one of the R2R3 Myb P-to-A genes, shares a common ancestor with P1, and appears to control the accumulation of phenylpropanoid compounds related to those controlled by P1, but is unlikely to participate in the control of flavonoid accumulation. read more....

Regulatory Networks Participating in Trichome Development

Position-dependent cell fate determination and pattern formation are unique aspects of the development of plant structures. The establishment of single-celled leaf hairs (trichomes) from pluripotent epidermal (protodermal) cells in Arabidopsis thaliana provides a powerful system to determine the genetic/regulatory networks and positional signals involved in cell fate determination. read more....

Arabidopsis Stomatal Development

Stomata, as the gate for gas exchange and water vapor, are essential for plant survival. In recent years, more and more studies focused on stomata development. Many genes were identified that are involved in controlling different stages during stomata development, such as TMM, YODA, MUTE, ER, FAMA, FLP and MYB88. Our interest focuses on the function of FLP/AtMYB88 in stomata development, research that is being carried in collaboration with Dr. Fred Sack. Based on the clustered guard cells phenotype in the flp mutant (four lips), FLP is suggested to participate in the transition of division to differentiation of guard cells. Uncovering the molecular function of FLP will lead to better understand how FLP control stomata development. Our biochemical and genetic data showed that FLP, as a MYB protein, is a transcription factor with a distinct DNA-binding specificity. By using microarray and ChIP-chip approaches, we have started to identify the direct targets of FLP during stomata development, uncovering unique mechanisms by which this atypical R2R3-MYB transcription factor regulates stomatal development. read more....

Establishing Regulatory Networks in Arabidopsis

Gene regulatory information is encoded in the promoter regions formed by cis-regulatory elements that bind specific transcription factors (TFs). Hence, establishing the architecture of plant promoters is fundamental to understanding gene expression. AGRIS (http://arabidopsis.med.ohio-state.edu) is an information resource of Arabidopsis promoter sequences, TFs, and their target genes. read more....

Plants produce a very large number of specialized compounds that must be transported from their site of synthesis to the sites of storage or disposal. Anthocyanin accumulation has provided a powerful system to elucidate the molecular and cellular mechanisms associated with the intracellular trafficking of phytochemicals. We recently showed (Poustka et al; 2007) that Arabidopsis anthocyanin are transported to the vacuole trough vesicle-like structures shared with components of the secretory pathway and in a Golgi-independent manner. We hypothesis that two mechanisms for anthocyanin cellular transport, one involving transporters and one involving vesicles, coexist in a plant cell or might be both part of a common trafficking pathway. read more....

Phlobaphene biosynthesis in maize

In maize, at least two flavonoid biosynthetic pathways have been characterized that are regulated independently. One pathway results in 3-hydroxy flavonoids such as anthocyanins purple pigment, whereas the other pathway produces 3-deoxy flavonoids such as the phlobaphene red pigment accumulated in kernel pericarp, silks and cob. read more...

 

Surface Flavonoids: Distribution, Function and Pharmacological Activities

A long standing interest of the lab has been the study of flavonoids. More recently, we have started to investigate those flavonoids that accumulate on plant surfaces, known as “surface, exudate, or external flavonoids”. We are interested in understanding the distribution pattern of surface flavonoids in the plant kingdom. We have started investing the occurrence of surface flavonoids in the grasses. We want to know whether the accumulation of surface flavonoids is a characteristic of a plant family or genus, or whether it is a curiosity of a few species within a genus. read more....

Flavonols are one group of phytochemicals that have important bioactivities in plants, animals and microorganisms, which play central roles in plant biology. However, the identification of the small molecules that carry out biological activities on flavonol protein targets provides a formidable bottleneck for metabolic engineering. Our research interest is to study how flavonols function as signal molecules by binding to particular cellular proteins, and to identify and characterize these targets. We are developing a chemical-biology approach that relies on detecting interactions of proteins with photoaffinity-tagged flavonol analogs in maize and Arabidopsis. This approach is termed as METSCREEN (screen with metabolites). read more....