Drought is one of the environmental factors that severely restrict plant
distribution and crop production. Previous studies have reported that the
high-affinity potassium transporter OsHAK1 plays important roles in
potassium acquisition and translocation in rice. However, knowledge on the
regulatory roles of OsHAK1 in drought stress is limited. The team of Guang
Chen from China National Rice Research Institute now aims to elucidate its
role in drought stress regulation.

The transcript levels of OsHAK1 were found to be elevated by water deficit
in roots and shoots. Under drought conditions, the OsHAK1 knockout mutants
(KO) exhibited lower drought tolerance and displayed stunted growth. The
OsHAK1 overexpression seedlings (Ox) showed better tolerance to drought
stress than wild types. Further analysis revealed that OsHAK1 acts 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
potassium homeostasis and stress responses in the transgenic plants under
dehydration.

Most importantly, OsHAK1-Ox plants displayed enhanced drought tolerance at
the reproductive stage, resulting in 35% more grain yield than wild types
under drought conditions. This study shows that OsHAK1 can be considered in
molecular breeding for improvement of drought tolerance in rice.

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