Rf 8-Mediated Turf 13 Transcript Accumulation Coincides with a Pentatricopeptide Repeat Cluster on Maize Chromosome 2 L

Cytoplasmic male sterility (CMS) is a maternally inherited inability to produce functional pollen. In Texas (T)-cytoplasm maize (Zea mays L.), CMS results from the action of the URF13 mitochondrial pore-forming protein encoded by the unique T-urf13 mitochondrial gene. Full or partial restoration of fertility to T-cytoplasm maize is mediated by the Rf2a nuclear gene in combination with one of three other genes: Rf1, Rf8, or Rf*. Rf2a encodes a mitochondrial aldehyde dehydrogenase whereas Rf1, Rf8, and Rf* are associated with the accumulation of distinctive T-urf13 mitochondrial transcripts. Rf8-associated RNA processing activity was mapped to a 4.55-Mbp region on chromosome 2L that contains 10 pentatricopeptide repeat (PPR) encoding genes in the B73 5b.60 genome assembly. Genetic linkage analysis also indicated that Rf* is positioned within this PPR cluster as well as Rf3, which restores USDA (S)-cytoplasm maize. Partially male-fertile plants segregated for the presence or absence of the Rf8-associated T-urf13 1.42and 0.42-kbp transcripts, indicating that the RNA processing event associated with these transcripts is not necessary for anther exsertion. In addition, a statistically signifi cant delay in fl owering was observed between partially male-fertile and mostly male-fertile plants. Taken together, these new results indicate that Rf8-mediated male fertility is under the control of more than one nuclear locus. CYTOPLASMIC MALE STERILITY (CMS) is caused by a maternally inherited inability to produce functional pollen. In maize (Zea mays L.), there are three types of CMS, USDA (S), Charrua (C), and Texas (T) (Beckett, 1971). Male sterility in T-cytoplasm maize (designated cms-T) results from the action of a T-cytoplasm specifi c mitochondrial gene, T-urf13 (Dewey et al., 1987; Wise et al., 1987b). Th is gene encodes 13 kDa monomers, which are assembled as tetrameric pore-forming structures that span the inner mitochondrial membrane (Korth et al., 1991; Rhoads et al., 1994). Th e presence of the 13 kDa URF13 protein also confers sensitivity to long-chain β-polyketol toxins produced by race T of the ascomycete fungus Cochliobolus heterostrophus (asexual stage Bipolaris maydis), the casual agent of southern corn leaf blight (Kono and Daly, 1979; Kono et al., 1980). Published in The Plant Genome 4:283–299. Published 29 Aug. 2011. doi: 10.3835/plantgenome2011.05. 0017 © Crop Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA An open-access publication All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. J. Meyer, D. Pei, and R.P. Wise, Interdepartmental Genetics Program, Iowa State Univ., Ames, IA 50011; and Department of Plant Pathology and Microbiology, Iowa State Univ., Ames, IA 50011; J. Meyer, present address: Regulatory Sciences Product Characterization Center, Monsanto, St. Louis, MO 63167; D. Pei, present address: Dep. of Biostatistics, St. Jude’s Children Research Hospital, Memphis, TN 38105; R.P. Wise, USDA-ARS, Crop and Insect Genetics, Genomics, and Informatics Research Unit, Iowa State Univ., Ames, IA 50011. Received 27 May 2011. *Corresponding author (rpwise@iastate.edu). Abbreviations: AFLP, amplifi ed fragment length polymorphism; ALDH, aldehyde dehydrogenase; BSA-AFLP, bulk segregant analysis amplifi ed fragment length polymorphism; BT, Boro II; CAPS, cleaved amplifi ed polymorphic sequence; CMS, cytoplasmic male sterility; cms-S, S-cytoplasm maize; cms-T, T-cytoplasm maize; CTAB, hexadecyltri-methylammonium bromide, DAPFF, days after planting to the fi rst fl owering; EDTA, ethylenediaminetetraacetic acid; HL, Honglian; mRNA, messenger RNA; N, normal; PCR, polymerase chain reaction; PPR, pentatricopeptide repeat; RAPD, random amplifi ed polymorphic DNA; Rf, restorer of fertility; RFLP, restriction fragment length polymorphism; S, USDA; SDS, sodium dodecyl sulfate; SSPE, saline sodium phosphate EDTA; T, Texas; TPR, tetratricopeptide repeat; UTR, untranslated region.