β-Amino-butyric acid protects Arabidopsis against low potassium stress

Potassium (K+) is an essential element for plant growth and development. Under low-K+ stress, Arabidopsis (Arabidopsis thaliana) plants show K+-deficient symptoms, typically leaf chlorosis and subsequent inhibition of plant growth and development. The non-protein amino acid beta-amino-butyric acid (BABA) has been shown to have roles in protecting Arabidopsis against various pathogens as well as drought, high salinity, and cadmium stresses; However, little is known about the role of BABA in protecting Arabidopsis against low-K+ stress. Here, we showed that BABA protects Arabidopsis against low-K+ stress by increasing K+ uptake under low-K+ condition. Leaf chlorosis of plants subjected to low-K+ stress was abolished by BABA pretreatment, as indicated by a lower reduction in chlorophyll content in BABA-treated plants than water-treated plants. Low-K+ stress-induced decreases in both lateral root length and the numbers of lateral roots were improved by BABA pretreatment. In addition, under low-K+ stress, a significantly higher K+ concentration was detected in BABA-pretreated plants than in water-treated plants, and the transcript levels of AtHAK5 and LKS1 genes involved in K+ uptake in BABA-treated plants were higher than those of water-treated plants. Taken together, our results suggest that BABA plays a role in enhancing low-K+ stress tolerance by increasing K+ uptake, at least in part, via modulation of AtHAK5 and LKS1 under low-K+ condition.