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CELL BIOLOGY AND SIGNAL TRANSDUCTION

ROOT UV-B SENSITIVE2 Acts with ROOT UV-B SENSITIVE1 in a Root Ultraviolet B-Sensing Pathway^1,[C],[OA]

Department of Biology, San Francisco State University, San Francisco, California 94132

Ultraviolet B light (UV-B; 280–320 nm) perception and signaling are well-known phenomena in plants, although no specific UV-B photoreceptors have yet been identified. We previously reported on the root UV-B sensitive1 (rus1) mutants in Arabidopsis (Arabidopsis thaliana), which display a block to development under very-low-fluence-rate UV-B (<0.1 µmol m^–2 s^–1) after the seedling emerges from the seed. Here, we report the analysis and cloning of the rus2-1 mutation in Arabidopsis. The phenotype of rus2-1 mutant seedlings is virtually indistinguishable from the phenotype of rus1 seedlings. A map-based approach was used to clone RUS2. RUS2 encodes a domain of unknown function (DUF647)-containing protein that is homologous to the RUS1 protein. rus1-2 rus2-1 double mutant seedlings have the same phenotype as both rus1 and rus2 single mutants, suggesting that the two genes work in the same pathway. RUS2-Green Fluorescent Protein shows a similar expression pattern as that of RUS1-Green Fluorescent Protein, and RUS1 and RUS2 proteins interact physically in yeast. This protein-protein interaction depends on the DUF647 domain, and site-directed mutagenesis identified specific residues in DUF647 that are required for both protein-protein interaction and physiological function. Six RUS genes are found in Arabidopsis, rice (Oryza sativa), and moss (Physcomitrella patens), and one RUS member, RUS3, is conserved in plants and animals. Our results demonstrate that RUS2 works with RUS1 in a root UV-B-sensing pathway that plays a vital role in Arabidopsis early seedling morphogenesis and development.

² These authors contributed equally to the article.

³ Present address: Genentech, Inc., 1 DNA Way, South San Francisco, CA 94080.

⁴ Present address: Laboratory of Molecular Plant Physiology, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Zheng-Hui He (zhe{at}sfsu.edu).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.109.139253

^* Corresponding author; e-mail zhe{at}sfsu.edu.

Received March 30, 2009; accepted June 6, 2009; published June 10, 2009.

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