Aquaporin expression and changes in fatty acid levels in apple leaves subjected to partial root-zone irrigation

ABSTRACT Partial root-zone drying (PRD) can induce changes in levels of the membrane fatty acids, transporter channels such as aquaporins (AQPs) and drought stress-responsive transcription factors (TFs) expression. The apple (Malus domestica (Suckow) Borkh. cv. Braeburn) trees were exposed to different PRD treatments for two consecutive years. The plasma-membrane intrinsic proteins (PIP1;1) and tonoplast-intrinsic proteins (TIP1;1) AQPs presented the highest expression in alternate partial root-zone drying (APRD75) and fixed partial root-zone drying (FPRD75) treatments than FPRD50 and control throughout the entire irrigation season, which was 120-140-fold higher in these treatments during some times. The TFs were highly expressed in APRD75 and FPRD75 treatments. The highest unsaturated fatty acid content was observed in APRD75 and FPRD75 treatments, and the lowest saturated fatty acid content was obtained in FPRD50 in both years. In addition to improving the water use efficiency (WUE) and maintaining the yield, APRD75 and FPRD75 treatments had a higher jasmonic acid (JA) content than the control. These results implied that changes in levels of the membrane fatty acids, AQPs, JA and TFs induced by APRD75 and FPRD75 treatments may be one of the possible ways for apple trees to adapt to the changing environmental conditions caused by PRD.