Functional characterization of the PICKLE chromatin remodeling factor in Arabidopsis thaliana

Hui-Chun Li, Purdue University


DNA is wrapped around core histones to form the basic unit of chromatin, and chromatin is compacted into a higher order structure to enable appropriate storage in the nucleus. This tightly condensed structure needs to be unwrapped precisely for DNA replication, repair, and gene expression at various developmental stages. Chromatin remodeling factors are the major players in determining the status of chromatin to facilitate gene expression. Although it has been observed that mutations of chromatin remodeling factors are often associated with growth defect at different stages of development, a detailed analysis of when these proteins act has not been undertaken. An Arabidopsis chromatin remodeling factor, PICKLE (PKL), is proposed to repress gene expression during germination. Loss of PKL results in defective growth and development, such as the dwarf stature, delayed flowering, reduced apical dominance, and oil body and storage protein accumulation in primary root (pickle root). We have found that PKL protein is highly expressed in young dividing tissues, such as germinating seedlings and young embryos, where differentiation occurs. Our laboratory has found that PKL protein is localized in the nucleus in a PKL:eGFP translational fusion, which is consistent with the proposed function of PKL as a chromatin remodeling factor to regulate chromatin status in the nucleus. Our laboratory has generated transgenic lines that carry a hormone inducible version of PKL (PKL:GR). Glucocorticoid receptor (GR) is localized in the cytoplasm under non-inducible condition, and the translocation of GR from cytoplasm to nucleus is dependent on hormone application. It has been shown previously by our laboratory that PKL may act before germination to repress expression of certain genes, such as LEC1. With the inducible version of PKL, we found that hormone-dependent activation of PKL protein before germination rescues the pickle root phenotype. In addition, the pleiotropic shoot phenotype of pkl mutant can be rescued with hormone induction in PKL:GR plants. We observed that RNA expression of a plant homeotic gene (PHE1) is correlated with hormone-dependent activation of PKL protein after germination. Our data suggest that PKL protein functions at different developmental stages to regulate gene expression.




Ogas, Purdue University.

Subject Area

Molecular biology|Cellular biology

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