Identification and characterization of the strawberry KT/HAK/KUP transporter gene family in response to K+ deficiency.

The potassium (K⁺) transporter/high-affinity K⁺/K⁺uptake transporters (KT/HAK/KUP), which contribute to K⁺ uptake, transport and allocation, take an indispensible part in ion homeostasis, as well as in plant adaptation to disadvantageous environmental stresses. However, molecular mechanisms in terms of K⁺ nutrition in fruit crops are still largely unknown. In this work, we isolated 15 KT/HAK/KUP transporter genes in strawberry (designated as FveKUP1 to FveKUP15), and checked their expression under both normal and K⁺ deficient conditions. Quantitative real-time PCR analyses indicated that most FveKUPs were largely expressed in flowers, with a responsive expression to K⁺ deficiency. Among these FveKUPs, FveKUP8 was the most abundantly expressed gene in all tested tissues, and its expression was significantly reduced by K⁺ deficiency. Further functional complementation experiment in bacterial mutant indicated that FveKUP8 can utilize external K⁺ under neutral proton environment, and might be a dominant K⁺ transporter during the flowering of strawberry plants. Our findings suggest that FveKUP8 is involved in K⁺ homeostasis in strawberry, and could be used as a potential gene for the molecular breeding of high K⁺ efficiency plants. [ABSTRACT FROM AUTHOR]