OsHAK1, a High-Affinity Potassium Transporter, Positively Regulates Responses to Drought Stress in Rice
Monday, 2017/11/06 | 07:54:24
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Chen G, Liu C, Gao Z, Zhang Y, Jiang H, Zhu L, Ren D, Yu L, Xu G, Qian Q. Frontier in Plant Science; 01 November 2017, Article 8:1885. ABSTRACTDrought is one of the environmental factors that severely restrict plant distribution and crop production. Recently, we reported that the high-affinity potassium transporter OsHAK1 plays important roles in K acquisition and translocation in rice over low and high K concentration ranges, however, knowledge on the regulatory roles of OsHAK1 in osmotic/drought stress is limited. Here, transcript levels of OsHAK1 were found transiently elevated by water deficit in roots and shoots, consistent with the enhanced GUS activity in transgenic plants under stress. Under drought conditions, OsHAK1 knockout mutants (KO) presented lower tolerance to the stress and displayed stunted growth at both the vegetative and reproductive stages. Phenotypic analysis of OsHAK1 overexpression seedlings (Ox) demonstrated that they present better tolerance to drought stress than wild-type (WT). Compared to WT seedlings, OsHAK1 overexpressors had lower level of lipid peroxidation, higher activities of antioxidant enzymes (POX and CAT) and higher proline accumulation. Furthermore, qPCR analysis revealed that OsHAK1 act as a positive regulator of the expression of stress-responsive genes as well as of two well-known rice channel genes (OsTPKb and OsAKT1) involved in K homeostasis and stress responses in transgenic plants under dehydration. Most important, OsHAK1-Ox plants displayed enhanced drought tolerance at the reproductive stage, resulting in 35% more grain yield than WT under drought conditions, and without exhibiting significant differences under normal growth conditions. Consequently, OsHAK1 can be considered to be used in molecular breeding for improvement of drought tolerance in rice.
See: https://www.frontiersin.org/articles/10.3389/fpls.2017.01885/full
Figure 10: Overexpression of OsHAK1 improves drought resistance at reproductive stage. Rice plants were grown in pots and were fully irrigated by watering every day until the drought treatment. Drought stress was applied at the booting stage. Limited water supply (40% field capacity) was maintained throughout the experiment until completion of the life cycle and full watering was applied to controls, then agronomic traits were assayed. (A) Effective tiller number per plant. (B) Seed-setting rate. (C) 1000-seed grain weight. (D) Grain yield per plant. Data represent mean ± SE of five replicates. Significant differences between WT and OsHAK1-Ox lines are indicated with asterisks (P < 0.05, one-way ANOVA); ns, non-significant differences at that level of significance. |
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