Proteomic Analysis of Roots Response to Potassium Deficiency and the Effect of TaHAK1-4A on K+ Uptake in Wheat

Abstract

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.

Positive Regulatory Roles of Manihot esculenta HAK5 under K+ Deficiency or High Salt Stress

“…Under 10 µM KCl condition, MeHAK5 transgenic plants had better growth performance compared to WT plants, with higher biomass and shoot K + content and longer primary root lengths ( Figure 5 ), supporting the conclusion that HAK5 mainly functions in the range of 10–50 µM K + concentration [ 55 ]. These results are consistent with those in transgenic Arabidopsis plants overexpressing Ta HAK1-4A [ 62 ]. Thus, Me HAK5 functions in relation to high-affinity K + uptake under low potassium conditions.…”

“…HbHAK1 expressed in the yeast mutant CY162 exhibited a strong K + uptake capacity under extreme K + deficiency [ 41 ]. Furthermore, both wheat Ta HAK1-4A and Casuarina equisetifolia Ceq HAK6 have recently been shown to participate in high-affinity K + uptake under K + -deficient conditions [ 49 , 62 ]. In this study, MeHAK5 was expressed in the yeast mutant CY162.…”

The miR166d/TaCPK7-D Signaling Module Is a Critical Mediator of Wheat (Triticum aestivum L.) Tolerance to K+ Deficiency

“…K + channels and transporters are critical for the uptake of K + in wheat. For example, TaAKT1 contributes to the constitutive and inducible K + uptake by wheat roots [43], while TaHAK1-4A is important for the uptake of K + by LK-stressed wheat roots [44]. Another recent study indicated that TaHAK5 promotes wheat root elongation and K + uptake [45].…”