Cytoplasmic male sterility

We have previously shown that the expression of an unedited atp9 chimeric gene correlated with malesterile phenotype in transgenic tobacco plant. To study the relationship between the expression of chimeric gene and the male-sterile trait, hemizygous and homozygous transgenic tobacco lines expressing the antisense atp9 RNA were constructed. The antisense producing plants were crossed with a homozygous male-sterile line, and the Fl progeny was analyzed. The offspring from crosses between homozygous lines produced only male-fertile plants, suggesting that the expression antisense atp9 RNA abolishes the effect of the unedited chimeric gene. In fact, the plants restored to male fertility showed a dramatic reduction of the unedited atp9 transcript levels, resulting in normal flower development and seed production. These results support our previous observation that the expression of unedited atp9 gene can induce male sterility.The development of strategies to improve crop plants by the production of hybrid varieties is a major goal in plant breeding. Hybrid progeny often have a higher yield, increased resistance to disease, and an enhanced performance in different environments compared with the parental lines (1). Male sterility mutations that guarantee the outcrossing of naturally autogamic plant lines (2) have proven to be useful for the production of hybrid lines with increased crop productivity. However, hybrid production is limited to those species of plants in which male sterility mutations have been detected. Moreover, in certain plants, such as corn, wheat, rice, or tomato, where seeds and fruits are harvested products, a male fertility restorer system is required.Many male sterility mutations interfere with tapetal cell differentiation and/or function, indicating that this tissue is essential for the production of functional pollen grains (3-7).The tapetal cells are the target to produce engineered malesterile plants. In view of this, several authors have reported the production of transgenic male-sterile plants by the expression of degradative enzymes in tapetal cells (8)(9)(10) or by the inhibition of particular enzymes by antisense strategies (11). One interesting, naturally-occurring phenotype is cytoplasmic male sterility. Molecular analysis of cytoplasmic male sterility plants has shown the presence of chimeric genes arising from rearrangement of the mtDNA. The production of proteins encoded by the chimeric genes has been correlated with male-sterile phenotype, and it has been proposed that it affects mitochondrial function (12-14).The different nature of the genes involved in cytoplasmic male sterility plants reported so far suggests that mitochondrial impairment may be the common consequence of the different chimeric gene products. If this is true, then a mitochondrial dysfunction could also be produced by other means and male-sterile plants could be obtained. Recently, we have reported the production of male-sterile tobacco plants by expression of the unedited coding region of mitochondrial ...

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confidence: 99%

Transgenic male-sterile plant induced by an unedited atp9 gene is restored to fertility by inhibiting its expression with antisense RNA.

Zabaleta

Mouras

Hernould

et al. 1996

“…Sources of such a cytoplasmic male sterility (CMS) have been found in many different species of plants (1). In the maize and sorghum cytoplasmic male sterile lines, it has been demonstrated that the genetic information responsible for the CMS trait resides in the mitochondria (2)(3)(4) apparently as episomal DNA (5).…”

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confidence: 99%

Identification and characterization of double-stranded RNA associated with cytoplasmic male sterility in Vicia faba

Grill

Garger

1981

The cytoplasmic male sterility (CMS) trait of at least one line of Viea faba plants is always associated with the presence of high molecular weight double-stranded RNA in the leaf tissue extracts. Subcellular fractions of leaf tissue from CMS and fertile maintainer plants were initially analyzed in an attempt to locate, identify, and characterize the genetic material involved with the sterility trait. This CMS-associated high molecular weight RNA was found only in the cytosol of the "447" male sterile line ofV. faba plants and could not be isolated from the recurrent parent (maintainer), from lines that had been fertility-restored, or from lines that had reverted from the sterile condition. We have been able to move the CMS-associated RNA from donor to fertile host plants through a dodder bridge. These hosts not only contain the RNA but now exhibit a male sterile phenotype, as detected by visual examination of the flower, the pollen, morphological characteristics, and pollen staining ability.Male sterility is most useful for the production of commercial amounts of hybrid seed if the factors responsible for the trait are maternally inherited. Sources of such a cytoplasmic male sterility (CMS) have been found in many different species of plants (1). In the maize and sorghum cytoplasmic male sterile lines, it has been demonstrated that the genetic information responsible for the CMS trait resides in the mitochondria (2-4) apparently as episomal DNA (5). Research on these monocotyledonous plants has led to a transposon-like model for the mitochondrial CMS DNA (6). However, there has been very little research on the causes of CMS in the dicotyledonous plants. There have been suggestions that viruses or virus-like particles (VLPs) are responsible for the sterility in the broad bean plants (Vidafaba L.) and petunias (7-9).An electron microscopic study of "447" male sterile, maintainer, restored, and reverted V.faba lines has shown the presence of cytoplasmic spherical bodies (=70 nm in diameter) in only the male sterile plants (8). In a short report we have indicated that there are particles in the CMS plants that contain a family of double-stranded RNA (dsRNA) molecules (10); we now further characterize these nucleic acids and identify one of them as consistently being associated with the sterility trait.The dsRNA particle appears to have characteristics similar to a virus, leading us to help substantiate a mechanism of sterility which is quite different from that involving the episomal DNA in maize mitochondria. These results and the eventual transfer of the dsRNA agent and the CMS biological trait provide compelling biochemical evidence that cytoplasmic male sterility in the broad bean plant is caused by the presence of at least one dsRNA species. MATERIALS AND METHODSPlant Material. Seeds of V.faba L. were provided by D. A. Bond (Plant Breeding Institute, Cambridge, England) and P. Berthelem (Institut National de la Recherche Agronomique Station for Plant Improvement, LeRheu, France) or were purchased from...

“…Male sterility resulting from a failure to produce viable pollen is widespread among higher plants; in many cases the defect is maternally inherited, and the syndrome is classified as cytoplasmic male sterility (CMS) (10). Mitochondrial malfunction has been suggested as a general cause of CMS in plants (1).…”

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confidence: 99%

Maize mitochondria synthesize organ-specific polypeptides.

Newton¹,

Walbot²

1985

We detected both quantitative and qualitative organ-specific differences in the total protein composition of mitochondria of maize. Labeling ofisolated mitochondria from each organ demonstrated that a few protein differences are due to changes in the polypeptides synthesized by the organelle. The synthesis of developmental stage-specific mitochondrial polypeptides was found in the scutella of developing and germinating kernels. The approximately 13-kDa polypeptide synthesized by mitochondria from seedlings of the Texas (T) male-sterile cytoplasm was shown to be constitutively expressed in all organs of line B37T tested. Methomyl, an insecticide known to inhibit the growth of T sterile plants, was shown to be an effective inhibitor of protein synthesis in mitochondria from T plants.