부산대학교 도서관

Rhizosphere acidification is essential for iron (Fe) uptake into plant roots. Plasma membrane (PM) H + -ATPases play key roles in rhizosphere acidification. However, it is not fully understood how PM H + -ATPase activity is regulated to enhance root Fe uptake under Fe-deficient conditions. Here, we present evidence that cytochrome b 5 reductase 1 (CBR1) increases the levels of unsaturated fatty acids, which stimulate PM H + -ATPase activity and thus lead to rhizosphere acidification. CBR1 -overexpressing ( CBR1 -OX) Arabidopsis thaliana plants had higher levels of unsaturated fatty acids (18:2 and 18:3), higher PM H + -ATPase activity, and lower rhizosphere pH than wild-type plants. By contrast, cbr1 loss-of-function mutant plants showed lower levels of unsaturated fatty acids and lower PM H + -ATPase activity but higher rhizosphere pH. Reduced PM H + -ATPase activity in cbr1 could be restored in vitro by addition of unsaturated fatty acids. Transcript levels of CBR1 , fatty acids desaturase 2 ( FAD2 ), and fatty acids desaturase 3 ( FAD3 ) were increased under Fe-deficient conditions. We propose that CBR1 has a crucial role in increasing the levels of unsaturated fatty acids, which activate the PM H + -ATPase and thus reduce rhizosphere pH. This reaction cascade ultimately promotes root Fe uptake. [ABSTRACT FROM AUTHOR]