Wheat plant height locus RHT25 encodes a PLATZ transcription factor that interacts with DELLA (RHT1)

Abstract

Plant height is an important agronomic trait with a significant impact on grain yield, as demonstrated by the positive effect of the REDUCED HEIGHT (RHT) dwarfing alleles (Rht1b) on lodging and harvest index in the "Green Revolution" wheat varieties. However, these gibberellic acid (GA) insensitive alleles also reduce coleoptile length, biomass production, and yield potential in some environments, triggering the search for alternative GA-sensitive dwarfing genes. Here we report the identification, validation and characterization of the gene underlying the GA-sensitive dwarfing locus RHT25 in wheat. This gene, designated as PLATZ-A1 (TraesCS6A02G156600), is expressed mainly in the elongating stem and developing spike and encodes a plant-specific AT-rich sequence- and zinc-binding protein (PLATZ). Natural and induced loss-of-function mutations in PLATZ-A1 reduce plant height and its over-expression increases it, demonstrating that PLATZ-A1 is the causative gene of RHT25. PLATZ-A1 interacts physically and genetically with RHT1 (DELLA), and both genes have stronger effects on plant height in the presence of the wildtype than in the presence of the mutant allele of the other gene. These results suggest that PLATZ1 can modulate the effect of DELLA on wheat plant height. We identified four natural truncation mutations and one promoter insertion in PLATZ-A1 that are more frequent in modern varieties than in landraces, suggesting positive selection during wheat breeding. These mutations can be used to fine-tune wheat plant height and, in combination with other GA-sensitive dwarfing genes, to replace the GA-insensitive Rht1b alleles to search for grain yield improvements beyond those of the Green Revolution varieties. Significance StatementWe have identified and characterized a previously unknown gene controlling plant height in wheat and named it PLATZ1. Mutations in PLATZ1 reduce plant height while its overexpression results in taller plants. PLATZ1 is expressed mainly in elongating stems and developing spikes and interacts physically and genetically with the "Green Revolution" dwarfing gene REDUCED HEIGHT 1 (RHT1). We discovered five natural mutants in the A genome copy of PLATZ1 in common wheat that have been favored during breeding, suggesting an overall positive effect on wheat performance. These mutations can be used to fine-tune wheat plant height and, eventually, to replace the RHT1 dwarfing alleles that impose limitations on planting depth and grain yield potential in some environments.