Specific Incorporation of Polyunsaturated Fatty Acids into the sn-2 Position of Phosphatidylglycerol Accelerates Photodamage to Photosystem II under Strong Light.

Haruhiko Jimbo,Takashi Hirashima,Koki Yuasa,Hajime Wada,Kensuke Takagi,Sumie Keta,Makiko Aichi

doi:10.3390/ijms221910432

Abstract

Free fatty acids (FFAs) are generated by the reaction of lipases with membrane lipids. Generated polyunsaturated fatty acids (PUFAs) containing more than two double bonds have toxic effects in photosynthetic organisms. In the present study, we examined the effect of exogenous FFAs in the growth medium on the activity of photosystem II (PSII) under strong light in the cyanobacterium Synechocystis sp. PCC 6803 (Synechocystis). PUFAs but not monounsaturated fatty acids accelerated the rate of photodamage to PSII by inactivating electron transfer at the oxygen-evolving complex. Moreover, supplemented PUFAs were specifically incorporated into the sn-2 position of phosphatidylglycerol (PG), which usually contains C16 fatty acids at the sn-2 position in Synechocystis cells. The disruption of the gene for an acyl-ACP synthetase reduced the effect of PUFAs on the photoinhibition of PSII. Thus, the specific incorporation of PUFAs into PG molecules requires acyl-ACP synthetase and leads to an unstable PSII, thereby accelerating photodamage to PSII. Our results are a breakthrough into elucidating the molecular mechanism of the toxicity of PUFAs to photosynthetic organisms.

Highlights

Fatty acids (FAs) are essential components consisting of membrane lipids in living cells
To further investigate the effect of unsaturated FAs on photosynthesis, we examined the effect of several unsaturated Free fatty acids (FFAs) containing double bonds of different numbers, at different positions and with different configurations on the photoinhibition of photosystem II (PSII) (Figure 1a)
Photodamage to PSII was observed in the presence of lincomycin, an inhibitor of protein synthesis that is required for the repair of PSII (Figure 1b)

Summary

Introduction

Fatty acids (FAs) are essential components consisting of membrane lipids in living cells. FFAs have a broad diversity in terms of the chain length, number, and position of double bonds with cis/trans configuration Such a wide spectrum has different effects on photosynthetic activities, as reported in Synechocystis sp. A polyunsaturated FA (PUFA), α-linolenic acid (18:3∆9,12,15 ), increased the sensitivity of photosystem II (PSII) to lightinduced damage to photosynthesis (photoinhibition), which had toxic effects on cellular growth [1,2]. It inhibited photosynthetic activity, and the inhibition was mediated by its incorporation into membrane lipids via the action of the acyl-acyl carrier protein

Methods

Results

Conclusion