A nuclear restorer-of-fertility mutation disrupts accumulation of mitochondrial ATP synthase subunit alpha in developing pollen of S male-sterile maize.
Mitochondrial biogenesis and function depend upon the interaction of mitochondrial and nuclear genomes. Forward genetic analysis of mitochondrial function presents a challenge in organisms that are obligated to respire. In the S-cytoplasmic male sterility (CMS-S) system of maize, expression of mitochondrial open reading frames (orf355-orf77) conditions collapse of developing haploid pollen. Nuclear restorer-of-fertility mutations that circumvent pollen collapse are often homozygous lethal. These spontaneous mutations potentially result from disruption of nuclear genes required for mitochondrial gene expression, in contrast to homozygous-viable restorer-of-fertility alleles that function to block or compensate for the expression of mitochondrial CMS genes. Consistent with this hypothesis, the homozygous-lethal restoring allele historically designated RfIII was shown to be recessive in diploid pollen produced by tetraploid CMS-S plants. Accordingly, the symbol for this allele has been changed to restorer-of-fertility lethal 1 (rfl1). In haploid rfl1 pollen, orf355-orf77 transcripts and mitochondrial transcripts encoding the alpha-subunit of the ATP synthase (ATPA) were decreased in abundance. Haploid rfl1 pollen failed to accumulate wild-type levels of ATPA protein, indicating that functional requirements for mitochondrial protein accumulation are relaxed in maize pollen. The CMS-S system and rfl mutations therefore allow for the selection of nuclear mutations disrupting mitochondrial biogenesis in a multicellular eukaryote.
Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611-0690, USA.
Lanying
L
Wen
Kimberly L
KL
Ruesch
Victor M
VM
Ortega
Terry L
TL
Kamps
Susan
S
Gabay-Laughnan
Christine D
CD
Chase
D000483:Alleles; D007246:Infertility / Q000235:genetics* / Q000378:metabolism; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism*; D011058:Pollen / Q000235:genetics* / Q000378:metabolism; D012150:Polymorphism, Restriction Fragment Length; D011506:Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism
D011506:Proteins; D012313:RNA; D025261:Mitochondrial Proton-Translocating ATPases