DOI:10.1093/pcp/pcaa080

Zhou Li, Jieru Hou, Yan Zhang, Weihang Zeng, Bizhen Cheng, Muhammad Jawad Hassan, Youzhi Zhang, Qi Pu, Yan Peng

Abstract：

Spermine (Spm) regulates water balance involved in water channel proteins, aquaporins (AQPs), in plants. An increase in endogenous Spm content via exogenous Spm application significantly improved cell membrane stability, photosynthesis, osmotic adjustment (OA) and water use efficiency (WUE) contributing to enhanced tolerance to water stress in white clover. Spm upregulatedTrTIP2-1,TrTIP2-2andTrPIP2-7expressions and also increased the abundance of TIP2 and PIP2-7 proteins in white clover under water stress. Spm quickly activated intracellular Ca²⁺signaling and Spm-inducedTrTIP2-2andTrPIP2-7expressions could be blocked by Ca²⁺channel blockers and the inhibitor of Ca²⁺-dependent protein kinase in leaves of white clover.TrSAMSin relation to Spm biosynthesis was first cloned from white clover and theTrSAMSwas located in the nucleus. Transgenic Arabidopsis overexpressing theTrSAMShad significantly higher endogenous Spm content and improved cell membrane stability, photosynthesis, OA, WUE and transcript levels ofAtSIP1-1, AtSIP1-2, AtTIP2-1, AtTIP2-2, AtPIP1-2, AtPIP2-1andAtNIP2-1than wild type in response to water stress. Current findings indicate that Spm regulates water balance via an enhancement in OA, WUE and water transport related to Ca²⁺-dependent AQP expression in plants under water stress.