Potassium (K⁺) is essential for plant growth and stress responses. A deficiency in soil K⁺ contents can result in decreased wheat quality and productivity. Thus, clarifying the molecular mechanism underlying wheat responses to low-K⁺ (LK) stress is critical. In this study, a tandem mass tag (TMT)-based quantitative proteomic analysis was performed to investigate the differentially abundant proteins (DAPs) in roots of the LK-tolerant wheat cultivar “KN9204” at the seedling stage after exposure to LK stress. A total of 104 DAPs were identified in the LK-treated roots. The DAPs related to carbohydrate and energy metabolism, transport, stress responses and defense, and post-translational modifications under LK conditions were highlighted. We identified a high-affinity potassium transporter (TaHAK1-4A) that was significantly up-regulated after the LK treatment. Additionally, TaHAK1-4A was mainly expressed in roots, and the encoded protein was localized in the plasma membrane. The complementation assay in yeast suggested that TaHAK1-4A mediates K⁺ uptake under extreme LK conditions. The overexpression of TaHAK1-4A increased the fresh weight and root length of Arabidopsis under LK conditions and improved the growth of Arabidopsis athak5 mutant seedlings, which grow poorly under LK conditions. Moreover, silencing of TaHAK1-4A in wheat roots treated with LK stress decreased the root length, dry weight, K⁺ concentration, and K⁺ influx. Accordingly, TaHAK1-4A is important for the uptake of K⁺ by roots exposed to LK stress. Our results reveal the protein metabolic changes in wheat induced by LK stress. Furthermore, we identified a candidate gene potentially relevant for developing wheat lines with increased K⁺ use efficiency.

It is well established that potassium (K⁺) is an essential nutrient for wheat (Triticum aestivum L.) growth and development. Several microRNAs (miRNAs), including miR166, are reportedly vital roles related to plant growth and stress responses. In this study, a K⁺ starvation-responsive miRNA (miR166d) was identified, which showed increased expression in the roots of wheat seedlings exposed to low-K⁺ stress. The overexpression of miR166d considerably increased the tolerance of transgenic Arabidopsis plants to K⁺ deprivation treatment. Furthermore, disrupting miR166d expression via virus-induced gene silencing (VIGS) adversely affected wheat adaptation to low-K⁺ stress. Additionally, miR166d directly targeted the calcium-dependent protein kinase 7-D gene (TaCPK7-D) in wheat. The TaCPK7-D gene expression was decreased in wheat seedling roots following K⁺ starvation treatment. Silencing TaCPK7-D in wheat increased K⁺ uptake under K⁺ starvation. Moreover, we observed that the miR166d/TaCPK7-D module could affect wheat tolerance to K⁺ starvation stress by regulating TaAKT1 and TaHAK1 expression. Taken together, our results indicate that miR166d is vital for K⁺ uptake and K⁺ starvation tolerance of wheat via regulation of TaCPK7-D.

Spike length is a critical trait influencing the yield potential of wheat (Triticum aestivum L.). However, there has been limited research on spike-length-related genes in wheat. Moreover, the scarcity of stable markers for spike-related traits has restricted marker-assisted selection-based breeding. In this study, a novel long-spike mutant material (LS1) was generated from wheat variety ‘Aikang 58’ (AK58) using ethyl methanesulfonate. We established an F₂ segregating population by crossing AK58 with LS1. Morphological analyses of this population indicated that spike length is a dominant quantitative trait regulated by multiple genes. Bulked segregant analysis (BSA) technology was used to preliminarily identify nine candidate regions associated with spike length traits. These regions were mainly in a 7.22 Mb interval (673.84–713.26 Mb) on chromosome 5A and in a 2.34 Mb interval (714.83–717.69 Mb) on chromosome 7B. Twelve candidate genes were identified within these regions. Furthermore, two kompetitive allele specific polymerase chain reaction (KASP) markers (KASP-LS1-681460621 and KASP-LS1-692013966) associated with spike length traits were developed. Both KASP markers effectively genotyped parental lines and the F₂ population. Our study results provide a theoretical foundation for the genetic improvement of spike-length-related traits in wheat.