G6PDH activity highlights the operation of the cyclic electron flow around PSI in Physcomitrella patens during salt stress.

Shan Gao,Zhenbing Zheng,Guangce Wang,Li Huan

doi:10.1038/srep21245

Abstract

Photosynthetic performances and glucose-6-phosphate dehydrogenase (G6PDH) activity in Physcomitrella patens changed greatly during salt stress and recovery. In P. patens, the cyclic electron flow around photosystem (PS) I was much more tolerant to high salt stress than PSII. After high salt stress, the PSII activity recovered much more slowly than that of PSI, which was rapidly restored to pretreatment levels even as PSII was almost inactivate. This result suggested that after salt stress the recovery of the cyclic electron flow around PSI was independent of PSII activity. In addition, G6PDH activity and NADPH content increased under high salt stress. When G6PDH activity was inhibited by glucosamine (Glucm, a G6PDH inhibitor), the cyclic electron flow around PSI and the NADPH content decreased significantly. Additionally, after recovery in liquid medium containing Glucm, the PSI activity was much lower than in liquid medium without Glucm. These results suggested the PSI activity was affected significantly by G6PDH activity and the NADPH content. Based on the above results, we propose that G6PDH in P. patens has a close relationship with the photosynthetic process, possibly providing NADPH for the operation of the cyclic electron flow around PSI during salt stress and promoting the restoration of PSI.

Highlights

Cells and is required for plant protection against oxidative damage because many environmental conditions induce oxidative stress
After 30 min of recovery in liquid medium, even though the PSII activity was not restored, the PSI activity was rapidly restored, and after 120 min of recovery, it was almost restored to the pretreatment level
The results suggested that the PSI in the gametophores of P. patens demonstrated a higher degree of tolerance to high salt stress than PSII and after treatments with high salt solution, the recovery of PSI activity was independent of the recovery of PSII activity

Summary

Introduction

Cells and is required for plant protection against oxidative damage because many environmental conditions induce oxidative stress. NADPH can donate electrons to the photosynthetic electron flow[12,24] This raises the question of whether the OPPP provides NADPH for the operation of the cyclic electron flow around PSI during recovery. The aim of this work was to study the responses of the photosynthetic electron flow and G6PDH in P. patens to high salt stress and the physiological link between the two processes. Particular attention was paid to the restoration of PSI and PSII during recovery and the responses of G6PDH activity and NADPH content to salt stress. The data obtained demonstrate that G6PDH has a close relationship with the photosynthetic process and might provide NADPH for the operation of the photosynthetic electron flow and the promotion of PSI restoration

Objectives

Methods

Results