Multicellular living organisms and unmodified parts thereof and – Method of using a plant or plant part in a breeding process... – Method of breeding using gametophyte control
Reexamination Certificate
1995-11-07
2001-01-09
Benzion, Gary (Department: 1638)
Multicellular living organisms and unmodified parts thereof and
Method of using a plant or plant part in a breeding process...
Method of breeding using gametophyte control
C800S271000, C800S268000, C800S320100, C800S303000, C536S024100, C536S023500, C536S023600, C536S023700
Reexamination Certificate
active
06172279
ABSTRACT:
This invention relates to a method for the production of hybrid plants. More particularly, the invention relates to the molecular control of fertility in crop plants.
Agriculture uses many crop plants for the production of food for human consumption, for commercial processes yielding products for human consumption, for animal feedstuff production, for the development of industrial products and other purposes. The process invariably involves the planting by the farmer of seed which has been purchased from a seed producer. The product produced by the crop be it the whole plant, the seed or fruit of the plant, is harvested and is then used for the various food applications mentioned above. In addition to purchasing seed from a seed company, the farmer also may plant back some seed saved from a previous year's crop. This, however, is only economically useful for crops which are used as inbreds or outcrossed seed. It is not economically advantageous for hybrid crops, which are planted to realise the increase productivity achieved by heterosis. The major crops planted in the major agricultural regions are planted as hybrid crops, which guarantee the farmer considerable yield increases.
Production of hybrid seed by specialised seed companies is a costly and complicated process. The process involves the breeding and selection of inbred parental lines, which in suitable combinations give progeny which exhibit maximal adaptation to environmental conditions with realisation of maximal yield. For hybrid seed production inbreds are chosen as either male or female parent in a cross yielding F1 hybrid seed. As most crops are hermaphroditic, the female parent in a cross has to be emasculated in order to avoid self-pollination during seed production. For open pollinating plants like maize a special planting regime is used in order to minimise self-pollinating of the female parent. This involves the separation of those plants to be used as males from the female parents. This allows easy separation of F1 hybrid seed at the end of the season.
Emasculation can be achieved either mechanically as it is used for maize, manually as it is used for tomato, or chemically as it is used for wheat or rice, and genetically using cytoplasmic male sterility (CMS) or genetic incompatibility as it is used for oil seed rape, sugar beet and others. These approaches vary in their complexity of agricultural practices or plant manipulation, but have in common, that they are costly to administer, complex to carry out and relatively inefficient depending on which system is used. This inefficiency arises from the fact that fertile plants need to be sterilised for seed production, which takes place in very large acreages depending on the crop. Therefore, large scale manipulation of females need to be carried out. Treatments also need to yield seed which is viable in the next generation which the farmer plants.
An object of the present invention is to obviate or mitigate the aforesaid disadvantages.
According to the present invention there is provided a plant gene construct which includes a disrupter protein gene capable of disrupting the biogenesis of viable pollen, and a gene control sequence which includes a promoter sequence inducible by external application of an exogenous chemical inducer to a plant containing the construct.
Preferably, the control sequence includes an operator controlling said disrupter protein gene and a repressor gene encoding a repressor protein adapted to bind said disrupter protein gene operator, said repressor protein gene being under control of said chemically inducible promoter.
Preferably also the construct includes a male flower specific operator sequence operatively linked to said disrupter protein gene, for restricting expression of the disrupter protein gene to male flower parts of a plant.
The invention also provides transformed plants and plant parts such as cells, protoplasts and seeds incorporating the construct of the invention.
In a preferred embodiment of the invention there is provided a recombinant DNA construct for insertion into the genome of a plant to impart restorable male sterility thereto, comprising:
(a) a first gene promoter sequence responsive to the presence or absence of an exogenous chemical inducer,
(b) a gene encoding a repressor protein under control of the said first promoter sequence;
(c) an operator sequence responsive to the said repressor protein;
(d) a second gene promoter sequence expressible only in male parts of a plant; and,
(e) a gene encoding a protein inhibitor of a plant characteristic essential to the production of viable pollen;
whereby the presence or absence of the exogenous chemical inducer enables selection of male fertility or sterility.
Further according to the invention there is provided a plant which is restorably male sterile, in which said plant contains, stably incorporated in its genome, the recombinant DNA construct defined above.
It is preferred that the said first promoter promotes expression of the repressor protein in response to stimulation by the exogenous chemical inducer whereby in the absence of the chemical inducer no repressor protein is expressed to interact with the operator thus permitting expression of the gene encoding the inhibitor of male fertility and in the presence of the chemical inducer repressor protein is expressed thereby preventing expression of the gene encoding the inhibitor of male fertility and restoring the plant to the fertile state. Thus the construct of the invention contains several operatively linked sequences (a) above will be referred to for convenience as “the chemical switch”: (b) as “the repressor sequence” (c) as “the operator” (d) as “the MFS control” (i.e male flower specific control) and (e) as the disrupter gene. The essential elements of each of the sequences and their interaction will be described below with reference to the accompanying drawings.
This invention enables the production of inbreds which are rendered male sterile using various molecular techniques and approaches. These plants require a chemical switch system for the reversal of fertility (reversible male sterility; RMS). Both aspects of the system are inherited as Mendelian characters. This will be achieved through the insertion into the plant genome of the molecular elements required for the controlled function of RMS.
The invention can be used for any mono- or di-cotyledonous plant which the breeder or grower wants to produce as F1 hybrid seed and for which suitable transformation techniques are or become available, particularly maize, wheat, sunflower, oil seed rape, tomato and other vegetables, sugar beet and ornamental foliage and flowering plants. It has great advantages in reduction in crop management costs associated with F1 hybrid seed production, ease of purity control of hybrid seed, maintenance of RMS lines and populations, transfer of RMS between lines and populations etc.
In one specific application we shall describe the production of plants, particularly inbred plants, which are rendered sterile using molecular engineering approaches. These plants can be reversed to fertility using a chemical spray which leads to the restoration of fertility using a molecular control cascade. The method presented here consists of a number of individual components which are subject to separate patent applications which disclose wider applications of the components.
1. THE OVERALL PROCESS
FIG. 1
of the drawings is a block diagram of the DNA construct of the invention in the “male sterile” state. In the absence of the exogenous chemical inducer, the chemical switch is inactive and no repressor protein is expressed by the repressor sequence. In the absence of the repressor protein, the operator sequence permits expression of the disrupter protein in male specific tissue, expression being specifically directed to male parts of the plant by the presence of the MFS control sequence. The outcome being that the plant is male sterile, is unable to produce viable pollen and thus unable to self-pollinate. The practical utility
Bridges Ian George
Bright Simon William Jonathan
Greenland Andrew James
Schuch Wolfgang Walter
Benzion Gary
Pillsbury Madison & Sutro LLP
Zeneca Limited
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