Location: Plant, Soil and Nutrition ResearchTitle: Identification of a novel pathway involving a GATA transcription factor in yeast and possibly plant Zn uptake and homeostasis Author
Submitted to: Journal of Integrative Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/3/2014
Publication Date: 3/3/2014
Publication URL: http://www.ncbi.nlm.nih.gov/pubmed/24433538
Citation: Milner, M., Pence, N., Liu, J., Kochian, L.V. 2014. Identification of a novel pathway involving a GATA transcription factor in yeast and possibly plant Zn uptake and homeostasis. Journal of Integrative Plant Biology. 56(3):271-280. DOI: 10.1111/jipb.12169. Interpretive Summary: Zinc (Zn) is an essential plant micronutrient that often limits crop production as the soils on over thirty percent of the world’s arable lands are Zn deficient. Also, it is estimated that 2 billion people worldwide suffer from Zn deficiency. Therefore, research on understanding how plants acquire and accumulate this sparingly available micronutrient can provide the necessary information to improve both plant and human Zn nutrition. In this manuscript, we present and research on a unique plant species, Noccaea caerulescens, that accumulates Zn to very high levels in its leaves (100x the leaf Zn concentrations in normal plants) as well as its seed. We are using this plant as a model system to study how plants can very efficiently and effectively acquire Zn. Using a technique where we introduce Noccea genes into a yeast mutant defective in regulating its Zn transporters, preventing the yeast mutant from growing on low Zn, we identified two related plant genes called E2F genes that restored the mutant’s ability to grow on low Z. These two E2F genes encode plant transcription factors that regulate the expression of other genes. More detailed research showed that the E2F genes turn on the expression of a genes encoding a second class of transcription factors called GATAs. Thus we have identified a novel role for GATA genes in turning on the expression of yeast (and possibly plant) Zn transporter genes. These findings are helping us better understand how plants regulate at the molecular level the network of proteins involved in Zn uptake from the soil, and Zn accumulation in the portions of the plant consumed by humans. Thus these findings have implications for dealing with both plant and human Zn deficiency.
Technical Abstract: To gain a better understanding of the regulation of Zn homeostasis in plants and the degree of conservation of Zn homeostasis between plants and yeast, a cDNA library from the Zn/Cd hyperaccumulating plant species, Nocceae caerulescens, was screened for its ability to restore growth under Zn limiting conditions in the yeast mutant where the ZAP1 gene has been deleted. ZAP1 is a transcription factor that activates the Zn dependent transcription of genes involved in Zn uptake, including ZRT1, the yeast high affinity Zn transporter. From this screen two members of the E2F family of transcription factors were found to activate ZRT1 expression in a Zn independent manner. The activation of ZRT1 by the plant E2F proteins involves E2F-mediated activation of a yeast GATA transcription factor which in turn activates ZRT1 expression. A ZRT1 promoter region necessary for activation by E2F and GATA proteins is upstream of two zinc responsive elements previously shown to bind ZAP1 in ZRT1. This activation may not involve direct binding of E2F to the ZRT1 promoter. The expression of E2F genes in yeast does not replace function of ZAP1; instead it appears to activate a novel GATA regulatory pathway involved in Zn uptake and homeostasis that is not Zn responsive.