Independent replication of mitochondrial genes supports the transcriptional program in developing fiber cells of cotton (Gossypium hirsutum L.).
The mitochondrial genomes of flowering plants exist both as a "master circle" chromosome and as numerous subgenomic sublimons that are generated by intramolecular recombination. Differential stability or replication of these sublimons allows individual mitochondrial gene copy numbers to vary independently between different cell types and developmental stages. Our objective was to determine the relationship between mitochondrial gene copy number and transcript abundance in the elongating fiber cells of Upland cotton (Gossypium hirsutum L.). We compared RNA and DNA from cotton fiber cells at five developmental time points from early elongation through secondary cell wall thickening from the Ligon-lintless 2 (Li2) short fiber mutant and its wild type near isogenic line (NIL) DP5690. Mitochondrial gene copy number decreased from 3 to 8-DPA in the developing cotton fiber cells while transcript levels remained low. As secondary cell wall biosynthesis began in developing fibers, the expression levels and copy numbers of mitochondrial genes involved in energy production and respiration were up-regulated in wild type cotton DP5690. However, the short fiber mutant Li2, failed to increase expression of these genes, which include three subunits of ATP synthase, atp1, atp8 and atp9 and two cytochrome genes cox1 and cob. At the same time, Li2 failed to increase the copy numbers of these highly expressed genes. Surprisingly, we found that when mitochondrial genes were highly transcribed, they also had very high copy numbers. This observation suggests that in developing cotton fibers, increased mitochondrial sublimon replication may support increases in gene transcription.
Cotton Fiber Bioscience Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA. Electronic address: Gregory.thyssen@ars.usda.gov.
Gregory N
GN
Thyssen
Cotton Fiber Bioscience Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA; College of Agronomy, State Key Laboratory of Crop Biology, Shandong Agricultural University, Tai'an, Shandong 271018, China. Electronic address: Xianliang.song@ars.usda.gov.
Xianliang
X
Song
Cotton Fiber Bioscience Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA. Electronic address: Marina.naoumkina@ars.usda.gov.
Marina
M
Naoumkina
Cotton Fiber Bioscience Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA. Electronic address: Heejin.kim@ars.usda.gov.
Hee-Jin
HJ
Kim
Cotton Fiber Bioscience Research Unit, USDA-ARS-SRRC, 1100 Robert E. Lee Blvd, New Orleans, LA 70124, USA. Electronic address: david.fang@ars.usda.gov.
David D
DD
Fang
D032561:Cotton Fiber; D004272:DNA, Mitochondrial / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics; D018628:Gene Dosage; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D050259:Genes, Mitochondrial / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics; D003368:Gossypium / Q000166:cytology / Q000235:genetics* / Q000254:growth & development; D024101:Mitochondrial Proteins / Q000235:genetics; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics; D009154:Mutation; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics; D012313:RNA / Q000235:genetics; D000077278:RNA, Mitochondrial; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014158:Transcription, Genetic / Q000235:genetics*
D004272:DNA, Mitochondrial; D018744:DNA, Plant; D024101:Mitochondrial Proteins; D010940:Plant Proteins; D021122:Protein Subunits; D000077278:RNA, Mitochondrial; D018749:RNA, Plant; D012313:RNA; D003576:Electron Transport Complex IV; D025261:Mitochondrial Proton-Translocating ATPases
Cotton fiber cell development; Gossypium; Mitochondrial genome; Mitochondrial replication and transcription; Sublimon stoichiometric shifting