CsSAD1-silenced in tea leaves impaired drought tolerance by decreasing plasma membrane H ⁺-ATPase activity

Abstract

Drought stress is a negative regulatory factor that leads to reduced yield and quality. Unsaturated fatty acids controlled by SAD (stearic acid desaturase) play a key role in mediating membrane fluidity to cope with drought stress; however, the response of CsSAD1 to drought stress is poorly understood. In this study, CsSAD1-silenced leaves displayed weakened drought tolerance, accompanied by lower Fv/Fm and higher MDA levels. However, CsSAD1-overexpressing Arabidopsis exhibited an elevated tolerance to drought stress in pot experiments. Furthermore, CsSAD1-silenced leaves displayed reduced plasma membrane H⁺-ATPase activity, which promoted membrane potential depolarization and led to a massive K⁺ loss under PEG stress. In contrast, CsSAD1-overexpressing Arabidopsis showed higher plasma membrane H⁺-ATPase activity and alleviated membrane potential depolarization, which in turn mitigated K⁺ loss under drought stress. Moreover, an exogenous supply of Na₃VO₄ (P-type ATPases inhibitor) further indicated that the difference in K⁺ efflux in the transgenic plants was dependent on the plasma membrane H⁺-ATPase. Therefore, silencing CsSAD1 in tea leaves inhibited plasma membrane H⁺-ATPase activity, which was the primary factor contributing to the maintenance of K⁺ homeostasis and, consequently, drought tolerance in tea plants.

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