INCORPORATION OF SEQUENCE LISTING

A computer readable form of a sequence listing is filed with this application by electronic submission and is incorporated into this application by reference in its entirety. The sequence listing is contained in the file named Sequence_Listing_P34317US03.txt, which is 61,118 bytes in size (measured in operating system MS Windows) and created on Mar. 20, 2019.

FIELD OF THE INVENTION

The present invention relates to compositions and methods for modulating floral development and vegetative growth by genetic modification of crop plants to increase yield.

BACKGROUND

The transition from vegetative growth to flowering is a crucial process during plant development that is necessary for the production of grain yield in crop plants. There are four major pathways controlling flowering time in land plants that respond to environmental or developmental cues, including photoperiodism (i.e., day length), vernalization (i.e., response to winter cold), and plant hormones (e.g., gibberellins or GA), in addition to the autonomous (environmentally independent) pathways. Except for the GA and autonomous pathways, regulation of flowering in plants generally involves two central regulators of flowering time, CONSTANS (CO) and FLOWERING LOCUS C (FLC). The FLC gene is a floral repressor that regulates flowering in response to vernalization, whereas the CO gene is a floral activator that responds to photoperiod conditions. Under inductive photoperiodic conditions, CO activity in source leaves increases expression of FLOWERING LOCUS T (FT), which translocates to the meristem to trigger expression of downstream floral activating genes, including LEAFY (LFY), APETALA1 (AP1) and SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1). Other genes, such as FLOWERING LOCUS C (FLC) and TERMINAL FLOWER 1 (TFL1), act to inhibit the expression or activity of these genes.

Except for day length neutral plants, most flowering plants respond to daily photoperiodic cycles and are classified as either short day (SD) or long day (LD) plants based on the photoperiod conditions required to induce flowering. The photoperiod refers to the relative length or duration of light and dark periods within a 24-hour cycle. In general, long day plants tend to flower when the day length exceeds a photoperiod threshold (e.g., as the days are getting longer in the spring), whereas short day plants tend to flower when the day length falls below a photoperiod threshold (e.g., as the days are getting shorter after the summer solstice). In other words, SD plants flower as the days are getting shorter, while LD plants flower as the days are getting longer. Soybean is an example of a short day (SD) plant in which flowering is induced when plants are exposed to shorter daylight conditions.

Plant growers are always looking for new methods to manipulate the yield of a plant, especially to enhance the seed yield of agronomically important crops. Thus, there is a continuing need in the art for improved compositions and methods for increasing yields of various crop plants. It is presently proposed that improved crop yields may be achieved by enhancing agronomic traits related to flowering and reproductive development.

SUMMARY

According to a first aspect of the present invention, a recombinant DNA construct is provided comprising a polynucleotide sequence encoding a florigenic FT protein operably linked to a vegetative stage promoter. The florigenic FT protein encoded by the polynucleotide sequence may comprise an amino acid sequence having at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or least 99% identity to a sequence selected from the group consisting of SEQ ID NOs: 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20, or a functional fragment thereof. The polynucleotide sequence may also be at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, or least 99% identity to a sequence selected from the group consisting of SEQ ID NOs: 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19. The vegetative stage promoter may further be a meristem-preferred or meristem-specific promoter. DNA molecules and vectors comprising such a recombinant DNA construct are further provided.

According to a second aspect of the present invention, transgenic plants, plant cells, plant tissues and plant parts are further provided comprising an insertion of the recombinant DNA construct of the present invention into the genome of such plants, cells, tissues, and plant parts. A transgenic plant of the present invention may be homozygous or hemizygous for an insertion of the recombinant DNA construct. A transgenic plant may be a short day plant and/or a dicotyledonous plant. Depending on the plant species, transgenic plants of the present invention may produce more bolls, siliques, fruits, nuts, or pods per node of the transgenic plant, relative to a control or wild type plant not having the recombinant DNA construct. Transgenic plants of the present invention may also produce more flowers and/or floral racemes per node relative to a control or wild type plant not having the recombinant DNA construct.

According to a third aspect of the present invention, methods for producing a transgenic plant having improved yield-related traits or phenotypes are provided comprising (a) transforming at least one cell of an explant with a recombinant DNA construct comprising a polynucleotide sequence encoding a florigenic FT protein operably linked to a vegetative stage promoter; and (b) regenerating or developing the transgenic plant from the transformed explant. Such methods may further comprise (c) selecting a transgenic plant having one or more of the following traits or phenotypes: earlier flowering, longer reproductive or flowering duration, increased number of flowers per node, increased number of floral racemes per node, increased number of pods, bolls, siliques, fruits, or nuts per node, and increased number of seeds per node, as compared to a control plant not having the recombinant DNA construct.

According a fourth aspect of the present invention, methods are provided for planting a transgenic crop plant of the present invention at a normal or higher density in the field. According to some embodiments, methods are provided comprising: planting a transgenic crop plant at a higher density in the field, wherein the transgenic crop plant is transformed with a recombinant DNA construct comprising a polynucleotide sequence encoding a florigenic FT protein operably linked to a vegetative stage promoter. According to some of these embodiments, the vegetative stage promoter may be a meristem-preferred or meristem-specific promoter. For soybean, a higher density of about 150,000 to 250,000 seeds of the transgenic soybean plant may be planted per acre. For cotton, a higher density of about 48,000 to 60,000 seeds of the transgenic cotton plant may be planted per acre. For canola, a higher density of about 450,000 to 680,000 seeds of the transgenic canola plant may be planted per acre.

