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

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 overexpression increases plant height, demonstrating that PLATZ-A1 is the causative gene of RHT25. PLATZ-A1 and RHT1 show a significant genetic interaction on plant height, and their encoded proteins interact with each other in yeast and wheat protoplasts. 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 and search for grain yield improvements beyond those of the Green Revolution varieties.

A genome-wide association study unveils key chromosome regions involved in determining sodium accumulation in wheat under conditions of low potassium supply.

Improving nutrient use efficiency is an important objective in modern breeding programs. In this work, we examined potassium utilization efficiency (KUtE) and traits potentially related to it in a formerly genotyped, geographically diverse population of bread wheat (Triticum aestivum) under low potassium supply conditions. Our results unveil the existence of a large variation within the population for the traits examined. A genome-wide association study, based on a single-locus model, identified 15 markers associated with some of those traits. No marker-trait association was found using that tool for KUtE, but the use of a multi-locus approach suggested that additional marker-trait associations may be present, including whole-plant KUtE. Besides, the existence of a significant correlation between KUtE and sodium accumulation in shoots suggests the possibility of pyramiding traits associated with sodium homeostasis to improve this efficiency. In this regard, two discrete regions mapped on the long arm of chromosome 1B (1BLA and 1BLB) were associated with variation in sodium accumulation as detected with the single and multi-locus models used. Further exploration of the potential function of the genes placed in these regions, and their expression patterns, suggested likely candidates for this trait. Among the candidates placed in 1BLA region, we found TraesCS1B02G370500, TraesCS1B02G370600, and TraesCS1B02G370900, coding for putative Calcineurin B like proteins. Region 1BLB contain TraesCS1B02G388900 coding for a kinase and other genes including TraesCS1B02G389700, TraesCS1B02G389800 and TraesCS1B02G389900 coding for Ethylene-responsive transcription factors. The information here provided can be useful in breeding programs aimed to manipulate sodium accumulation through marker-assisted selection.

Barley plants carrying the altered function Sln1d allele display modified responses to low phosphorus supply: implications for phosphorus utilisation efficiency.

The module GA-GID1-DELLA (Gibberellin-Gibberellin Receptor-DELLA proteins) provides a point for the integration of signals potentially relevant in determining nutrient utilisation and acquisition efficiencies. In this study, we explored the role of components of this module during the acclimation of barley plants (Hordeum vulgare L.) to different phosphorus (P) supplies by using two related genotypes, harbouring either the WT or the Sln1d alleles of the DELLA-coding gene Sln1. Dwarf Sln1d plants exhibited reduced shoot P utilisation efficiency (PUtE) and better performance at low levels of P supply. The superior PUtE displayed by WT plants disappeared when corrected by internal P concentration, indicating that multiple analyses are necessary to fully understand the meaning of PUtE estimates. Over a wide range of external supplies of P, Sln1d plants displayed enhanced P concentration, which was associated with low relative growth rate, high biomass partitioning to roots and high P-uptake-rate, thus suggesting that the effect of the Sln1d allele on P dynamics is not simply a consequence of slow growth habit. An enhanced P concentration was also found in a mutant with defective GAs-synthesis. Our results suggest that components of the GA-GID1-DELLAs module contribute to set the acclimation response of barley plants to low P supply through both P-dynamics dependent and P-dynamics independent mechanisms.