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The Maize Zmsmu2 Gene Encodes a Putative RNA-Splicing Factor That Affects Protein Synthesis and RNA Processing during Endosperm Development^1,[W],[OA]

Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721 (T.C., C.S.K., H.N.N., B.A.L.); and Pioneer Hi-Bred International, a DuPont Company, Johnston, Iowa 50131–1004 (R.B.M.)

We characterized two maize (Zea mays) mutants, zmsmu2-1 and zmsmu2-3, that result from insertion of a Mutator (Mu) transposable element in the first exon of a gene homologous to the nematode gene, smu-2, which is involved in RNA splicing. In addition to having a starchy endosperm with reduced levels of zein storage proteins, homozygous zmsmu2-1 mutants manifest a number of phenotypes, including defective meristem development. The zmsmu2 mutants have poor seedling viability and surviving plants are sterile. The gene encoding ZmSMU2 is expressed in the endosperm, embryo, and shoot apex, which explains the pleiotropic nature of the mutation. We found that proper expression of Zmsmu2 is required for efficient ribosomal RNA processing, ribosome biogenesis, and protein synthesis in developing endosperm. Based on the pleiotropic nature of the mutations and the known function of animal Zmsmu2 homologs, we propose a possible role for ZmSMU2 in the development of maize endosperm, as well as a mechanism by which misregulation of zmsmu2 causes the mutant phenotypes.

² Present address: 425–G Henry Mall, Department of Genetics, University of Wisconsin, Madison, WI 53706.

³ Present address: Department of Plant Biotechnology and Agricultural Plant Stress Research Center, Chonnam National University, Kwangju 500–757, Korea.

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: Brian A. Larkins (larkins{at}ag.arizona.edu).

^[W] The online version of this article contains Web-only data.

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

www.plantphysiol.org/cgi/doi/10.1104/pp.107.096214

^* Corresponding author; e-mail larkins{at}ag.arizona.edu; fax 520–621–3692.

Received January 24, 2007; accepted March 6, 2007; published March 23, 2007.