Abstract
Polyamines can alleviate the inhibitory effects of salinity on plant growth by regulating photosynthetic efficiency. However, little information is available to explain the specific mechanisms underlying the contribution of polyamines to salt tolerance of the photosynthetic apparatus. Here, we investigated the role of putrescine (Put) on the photosynthetic apparatus of cucumber seedlings under salt stress. We found that NaCl stress resulted in severe ion toxicity and oxidative stress in cucumber chloroplasts. In addition, salinity caused a significant increase in the saturated fatty acid contents of thylakoid membranes. Put altered unsaturated fatty acid content, thereby alleviating the disintegration of thylakoid grana lamellae and reducing the number of plastoglobuli in thylakoid membranes. BN-PAGE revealed Put up-regulated the expression of ATP synthase, CP47, D1, Qb, and psbA proteins and down-regulated CP24, D2, and LHCII type III in NaCl-stressed thylakoid membranes. qRT-PCR analysis of gene expression was used to compare transcript and protein accumulation among 10 candidate proteins. For five of these proteins, induced transcript accumulation was consistent with the pattern of induced protein accumulation. Our results suggest that Put regulates protein expression at transcriptional and translational levels by increasing endogenous polyamines levels in thylakoid membranes, which may stabilise photosynthetic apparatus under salt stress.
Highlights
Some extent, alleviate salinity-induced decreases in photosynthetic efficiency of higher plants, but this effect strongly depends on both PA concentrations or types, and stress levels[8,9]
We found that there was a marked increase of H2O2 production in NaCl-stressed chloroplasts of stomatal cells compared with the controls
All the results suggest that Put alleviates salt stress-induced thylakoid membrane lipid peroxidation by enhancing unsaturated fatty acid content
Summary
Some extent, alleviate salinity-induced decreases in photosynthetic efficiency of higher plants, but this effect strongly depends on both PA concentrations or types, and stress levels[8,9]. The protective action of Spd in PSII can be explained by the involvement of PAs in the modulation of transcription and translation of these proteins Because of their polycationic nature at physiological pH, PAs are able to interact with negatively charged macromolecules such as proteins, nucleic acids, and chromatin, thereby stabilizing their structures. The potential roles of PAs in the protection of photosynthetic apparatus responses to abiotic stresses have been well studied, few reports have focussed on the specific mechanism underpinning the action of PAs on thylakoid membrane proteins of the photosynthetic apparatus of higher plants exposed to salt stress. Our previous results indicated that electrostatic interactions of PAs or their conjugation with proteins of PSII may help stabilize protein conformational structure and enhance chloroplast function in salt-stressed cucumber seedlings[1,8]. The results of this study provide insights into the mechanism by which PAs protect the structure and functions of the photosynthetic apparatus from NaCl-induced damage
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