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

Abstract

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 ...

An in vitro RNA editing system from cauliflower mitochondria: Editing site recognition parameters can vary in different plant species

“…These results thus suggest that the cis-elements have evolved between the two plant species, and it thus can be assumed that also the respective trans-elements have changed and presently differ between the pea and the cauliflower. Nevertheless, the basic mode of editing site specification has of necessity been conserved in evolution between these two flowering plants, since both definitely require this C-to-U alteration for a functional mitochondrial ATPase (Hernould et al 1993;Zabaleta et al 1996).…”

RNA editing in plant mitochondria, cytoplasmic male sterility and plant breeding

“…As detailed above male sterility was obtained by engineering plants able to synthesize an unedited mitochondrial protein in the cytosolic ribosomes which was further addressed to the mitochondria. Our approach to restore fertility was based on the antisense strategy (Zabaleta et al, 1996). The working hypthesis was that crossing the male-sterile plants produced as described above with plants expressing the same mRNA but in the antisense orientation should lead to the formation of a dsRNA.…”

“…Our approach to restore fertility was based on the antisense strategy (Zabaleta et al, 1996). The working hypthesis was that crossing the male-sterile plants produced as described above with plants expressing the same mRNA but in the antisense orientation should lead to the formation of a dsRNA.…”

A comparative study of ATPase subunit 9 (Atp9) gene between cytoplasmic male sterile line and its maintainer line in soybeans

“…Pollen abortion was induced after transforming an incompletely edited atp9 gene in tobacco; however, normal fertility remained the same after transforming a completely edited atp9 gene in tobacco (Hernould et al, 1993). Further study showed that the fertility of tobacco could be restored by inhibiting expression of the incompletely edited atp9 gene (Zabaleta et al, 1996). In addition, CMS was obtained by transforming unedited atp9 gene into tobacco (Araya et al, 1998).…”