Multicellular living organisms and unmodified parts thereof and – Plant – seedling – plant seed – or plant part – per se – Higher plant – seedling – plant seed – or plant part
Reexamination Certificate
1999-01-15
2001-07-17
Nelson, Amy J. (Department: 1638)
Multicellular living organisms and unmodified parts thereof and
Plant, seedling, plant seed, or plant part, per se
Higher plant, seedling, plant seed, or plant part
C800S283000, C800S286000
Reexamination Certificate
active
06262346
ABSTRACT:
BACKGROUND OF THE INVENTION
This application relates to DNAs, isolated from banana (
Musa
), DNA constructs containing the banana DNA, plant cells containing the constructs and plants derived therefrom. In particular it involves the use of antisense or sense RNA technology to control gene expression in plants.
Many physiological and developmental processes are controlled by ethylene in higher plants, including banana (Genus:
Musa
). These processes include fruit ripening where ethylene may be involved in both the initiation and rate of continuation of many of the changes involved in fruit ripening. However the exact role of ethylene has hitherto not been fully understood. We have now isolated a DNA involved in the generation of ethylene in bananas. In this invention, we provide such DNA, and methods of using it. One such use is a method for controlling the rate of production of ethylene in ripening bananas. In this way the rate of many of the ethylene-related changes associated with fruit ripening on a plant can be modified to obtain desired ripening characteristics.
The modification of plant gene expression has been achieved by several methods. The molecular biologist can choose from a range of known methods to decrease or increase gene expression or to alter the spatial or temporal expression of a particular gene. For example, the expression of either specific antisense RNA or partial (truncated) sense RNA has been utilised to reduce the expression of various target genes in plants (as reviewed by Bird and Ray, 1991, Biotechnology and Genetic Engineering Reviews 9:207-227). These techniques involve the incorporation into the genome of the plant of a synthetic gene designed to express either antisense or sense RNA. They have been successfully used to down-regulate the expression of a range of individual genes involved in the development and ripening of tomato fruit (Gray et al, 1992, Plant Molecular Biology, 19:69-87). Methods to increase the expression of a target gene have also been developed. For example, additional genes designed to express RNA containing the complete coding region of the target gene may be incorporated into the genome of the plant to “over-express” the gene product. Various other methods to modify gene expression are known; for example, the use of alternative regulatory sequences.
An object of the present invention is to provide new materials for use in the genetic control of ethylene biosynthesis in fruit, and hence ethylene-induced processes involved in fruit ripening, particularly banana fruit.
BRIEF SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a method of modifying ethylene biosynthesis in a plant comprising inserting into the genome of the said plant a DNA sequence which modifies the activity of at least one of ACS or EFE.
Preferably, the said ACS has the sequence SEQ-ID-NO-1 and the said EFE has the sequence SEQ-ID-NO-2.
In particular, the method may be used to modify fruit ripening characteristics, especially in bananas.
The levels of ethylene biosynthesis may be either reduced or increased during development and ripening depending on the ripening characteristics desired for the modified fruit. “Antisense” or “partial sense” or other techniques may be used to reduce the expression of either ACS or EFE in developing and ripening fruit. The levels of ACS or EFE may also be increased; for example, by incorporation of additional ACS or EFE genes. The additional genes may be designed to give either the same or different spatial and temporal patterns of expression in the fruit.
The present invention provides clones of genes which express enzymes involved in ethylene biosynthesis: 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and ethylene-forming enzyme (EFE). ACS and EFE are involved in ethylene production, and hence in the ripening of bananas. cDNA clones representing these genes have been cloned and characterised.
According to the present invention we provide cDNA clones representing at least part of genes derived from banana that encode either ACS or EFE. Example of such clones are clone pACS6 (ACS) and clone pACOS7 (EFE). We further provide DNA constructs comprising a DNA sequence homologous to some or all of genes derived from banana that encode either ACS or EFE, preceded by a transcriptional initiation region operative in plants, so that the construct can generate RNA in plant cells.
DETAILED DESCRIPTION OF THE INVENTION
cDNA clones encoding a ACS and EFE have been obtained from a banana fruit pulp cDNA library. The clones are hereinafter called pACS6 (ACS) and pACOS7 (EFE). The full nucleotide sequence of the ACS cDNA (clone pACS6) is given as SEQ ID NO 1 and that of the EFE cDNA (clone pACOS7)is given as SEQ ID NO 2.
An alternative source of the DNA sequence is a suitable gene encoding either ACS or EFE. This gene may differ from the corresponding cDNA in that introns may be present. The introns are not transcribed into mRNA (or, if so transcribed, are subsequently cut out). Oligonucleotide probes or the cDNA clone may be used to isolate the actual ACS or EFE gene(s) by screening banana genomic DNA libraries. Such genomic clones may include control sequences operating in the plant genome. Thus it is also possible to isolate promoter sequences which may be used to drive expression of the enzymes or any other protein. These promoters may be particularly responsive to certain developmental events (such as ripening) and environment conditions. Banana ACS or EFE gene promoters may be used to drive expression of any target gene.
ACS or EFE DNA sequence may be isolated from banana cDNA or genomic DNA libraries using oligonucleotide probes based on the pACS6 or pACOS7 sequences. A banana ACS DNA sequence is any sequence from banana which cross-hybridises with SEQ ID NO 1, preferably having at least 60% homology with SEQ ID NO 1. A banana ACS DNA sequence may encode a protein which is homologous to the predicted gene product encoded by SEQ ID NO 1. A banana EFE DNA sequence is any sequence from banana which cross-hybridises with SEQ ID NO 2, preferably having at least 60% homology with SEQ ID NO 2. A banana EFE DNA sequence may encode a protein which is homologous to the predicted gene product encoded by SEQ ID NO 2.
A further way of obtaining ACS and EFE DNA sequence is to synthesise it ab initio from the appropriate bases, for example using the appropriate cDNA sequence as a guide.
Some or all of the ACS or EFE sequences may be incorporated into DNA constructs suitable for plant transformation. These DNA constructs may then be used to modify ACS or EFE gene expression in plants. “Antisense” or “partial sense” or other techniques may be used to reduce ACS or EFE gene expression in plant tissue (down-regulation). The levels of expression may also be increased (up-regulation); for example, by incorporation of additional ACS or EFE genes. The additional genes may be designed to give either the same or different spatial and temporal patterns of expression in the plant.
According to a further aspect of the invention there is provided a DNA construct comprising some or all of a ACS or EFE DNA sequence under the control of a transcriptional initiation region operative in plants, so that the construct can generate RNA in plant cells.
The fruit ripening characteristics and related characteristics of plant parts may be modified by transformation with a DNA construct according to the invention. The invention also provides plant cells containing such constructs; plants derived therefrom having modified ACS or EFE gene expression; and seeds of such plants.
A DNA construct according to the invention may be an “antisense” construct generating “antisense” RNA or a “sense” construct (encoding at least part of the functional enzyme) generating “sense” RNA. “Antisense RNA” is an RNA sequence which is complementary to a sequence of bases in the corresponding mRNA: complementary in the sense that each base (or the majority of bases) in the antisense sequence (read in the 3′ to 5′ sense) is capable of
Bird Colin Roger
Fletcher Jonathon David
Hohenschutz Liza D.
Nelson Amy J.
Zeneca Limited
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