and , Partner Genes of a Transcription Repressor, Coordinate Plant Development and Drought Tolerance in Spelt and Bread Wheat.

Down-regulator associated protein, DrAp1, acts as a negative cofactor (NC2α) in a transcription repressor complex together with another subunit, down-regulator Dr1 (NC2β). In binding to promotors and regulating the initiation of transcription of various genes, plays a key role in plant transition to flowering and ultimately in seed production. and genes were identified, and their expression and genetic polymorphism were studied using bioinformatics, qPCR analyses, a 40K Single nucleotide polymorphism (SNP) microarray, and Amplifluor-like SNP genotyping in cultivars of bread wheat ( L.) and breeding lines developed from a cross between spelt ( L.) and bread wheat. was highly expressed under non-stressed conditions, and at flowering, expression was negatively correlated with yield capacity. showed a consistently low level of mRNA production. Drought caused changes in the expression of both and genes in opposite directions, effectively increasing expression in lower yielding cultivars. The microarray 40K SNP assay and Amplifluor-like SNP marker, revealed clear scores and allele discriminations for and and genes. Alleles of two particular homeologs, and , co-segregated with grain yield in nine selected breeding lines. This indicated an important regulatory role for both and genes in plant growth, ontogenesis, and drought tolerance in bread and spelt wheat.