Recombinant DNA constructs and methods for controlling gene expression
The present invention provides molecular constructs and methods for use thereof, including constructs including heterologous miRNA recognition sites, constructs for gene suppression including a gene suppression element embedded within an intron flanked on one or on both sides by non-protein-coding sequence, constructs containing engineered miRNA or miRNA precursors, and constructs for suppression of production of mature microRNA in a cell. Also provided are transgenic plant cells, plants, and seeds containing such constructs, and methods for their use. The invention further provides transgenic plant cells, plants, and seeds containing recombinant DNA for the ligand-controlled expression of a target sequence, which may be endogenous or exogenous. Also disclosed are novel miRNAs and miRNA precursors from crop plants including maize and soy.
1. A recombinant DNA construct comprising a promoter functional in a plant cell and operably linked to DNA that transcribes to RNA comprising:
(a) at least one exogenous miRNA recognition site recognizable by a mature miRNA, wherein said mature miRNA is encoded by a DNA sequence selected from SEQ ID NOs:36, 40, 41, or 42 and is expressed in a specific cell of a plant, and
(b) target RNA to be suppressed in said specific cell,
wherein said target RNA is to be expressed in cells of said plant other than said specific cell.
2. The recombinant DNA construct of claim 1 , wherein said at least one exogenous miRNA recognition site is located within at least one of:
(a) the 5′ untranslated region of said target RNA;
(b) the 3′ untranslated region of said target RNA; and
(c) said target RNA.
3. The recombinant DNA construct of claim 1 , wherein said target RNA comprises at least one of:
(a) non-coding RNA;
(b) a suppression element; and
(c) a gene expression element.
4. A transgenic plant comprising the recombinant DNA construct of claim 1 .
5. A method for suppressing expression of a target RNA in a specific cell of a plant, comprising transcribing in said plant the recombinant DNA construct of claim 1 , wherein said mature miRNA guides cleavage of target RNA in said specific cell, whereby expression of said target RNA is suppressed in said specific cell relative to its expression in cells lacking expression of said mature miRNA.
6. The method of claim 5 , wherein said recombinant DNA construct further comprises a gene expression element for expressing at least one gene of interest, and wherein said expression of said target RNA is suppressed with concurrent expression of said at least one gene of interest in said specific cell.
7. The method of claim 5 , wherein said plant is a crop plant.
8. The method of claim 5 , wherein said target RNA comprises a gene suppression element embedded in an intron flanked on one or on both sides by non-protein-coding DNA.
9. A transgenic plant cell having in its genome a recombinant DNA construct selected from the recombinant DNA construct of claim 1 .
10. The transgenic plant cell of claim 9 , wherein said transgenic plant cell is in at least one plant tissue selected from the group consisting of leaf, root, stem, stalk, wood, seed, fruit, and flower.
11. A method of providing at least one altered plant tissue, comprising transcribing said recombinant DNA construct in at least one tissue of said transgenic plant of claim 4 , whereby an altered trait in said at least one tissue results, relative to tissue wherein said recombinant DNA construct is not transcribed, said altered trait being selected from:
(i) improved abiotic stress tolerance;
(ii) improved biotic stress tolerance;
(iii) improved resistance to a pest or pathogen of said plant;
(iv) modified primary metabolite composition;
(v) modified secondary metabolite composition;
(vi) modified trace element, carotenoid, or vitamin composition;
(vii) improved yield;
(viii) improved ability to use nitrogen or other nutrients;
(ix) modified agronomic characteristics;
(x) modified growth or reproductive characteristics; and
(xi) improved harvest, storage, or processing quality.
12. The method of claim 11 , wherein said transgenic plant is a crop plant.
13. The transgenic plant of claim 4 , wherein said transgenic plant has at least one altered trait, relative to a plant lacking said recombinant DNA construct, selected from the group of traits consisting of:
(a) improved abiotic stress tolerance;
(b) improved biotic stress tolerance;
(c) improved resistance to a pest or pathogen of said plant;
(d) modified primary metabolite composition;
(e) modified secondary metabolite composition;
(f) modified trace element, carotenoid, or vitamin composition;
(g) improved yield;
(h) improved ability to use nitrogen or other nutrients;
(i) modified agronomic characteristics;
(j) modified growth or reproductive characteristics; and
(k) improved harvest, storage, or processing quality.
14. A seed of the transgenic plant of claim 13 , wherein said seed has modified primary metabolite, trace element, carotenoid, vitamin, or secondary metabolite composition, or improved storage or processing quality, and wherein said seed comprises said recombinant DNA construct.
15. The transgenic plant of claim 13 , wherein said transgenic plant is a crop plant.
16. A transgenic seed having in its genome the recombinant DNA construct of claim 1 .
17. A transgenic plant grown from the seed of claim 16 .