Characterization of Target Site of Aluminum Phytotoxicity in Photosynthetic Electron Transport by Fluorescence Techniques in Tobacco Leaves

Abstract

Aluminum (Al) toxicity limits crop yield in acidic soil through affecting diverse metabolic processes, especially photosynthesis. The aim of this work was to examine the effect of Al on photosynthetic electron transport in vivo as determined by chlorophyll fluorescence and delayed fluorescence of tobacco leaves. Results showed that Al treatment inhibited the photosynthetic rate and electron transfer, and decreased photosystem (PS) II photochemical activity in a time- and concentration-dependent manner, which could not be obviously alleviated by the addition of the reactive oxygen species (ROS) scavenger ascorbic acid (AsA). These results suggested that photosynthetic electron transfer chain components, especially PSII, might be directly damaged by Al instead of in an ROS-dependent manner. Furthermore, the fluorescence imaging and biochemical analysis exhibited that Al, after entering the cells, could accumulate in the chloroplasts, which paralleled the decreased content of Fe in the chloroplast. The changes in the chlorophyll fluorescence decay curve, the delayed fluorescence decay curve and the chlorophyll fluorescence parameters indicated that Al, through interacting with or replacing the non-heme iron between Q(A) and Q(B), caused the inhibition of electron transfer between Q(A) and Q(B), resulting in PSII photochemical damage and inhibition of the photosynthetic rate. In summary, our results characterized the target site of Al phytotoxicity in photosynthetic electron transport, providing new insight into the mechanism of Al phytotoxicity-induced chloroplast dysfunction and photosynthetic damage.

Characterization of the structural changes and photochemical activity of photosystem I under Al3+ effect

“…Under its trivalent cationic form, Al 3+ acts as a highly toxic non-essential element for plants growth causing a number of adverse effects on physiological and biochemical processes, especially the inhibition of photosynthetic activity. At this level, it was shown that Al 3+ inhibits photosynthetic electron transport in photosystem II (PSII), affects the PSII RC, destabilizes the oxygen evolution complex (OEC), impairs light harvesting complex (LHCII) antenna of PSII and induces a conformational changes of the secondary structure polypeptides of PSII [31][32][33][34][35][36][37][38].…”

Reactive oxygen species promote chloroplast dysfunction and salicylic acid accumulation in fumonisin B1‐induced cell death

“…Our early studies showed that protoplasts exhibited an increase of ROS levels in a light-dependent manner after UV-C irradiation [9]. Recently, some studies demonstrated that various stimuli, such as aluminum toxicity, methyl jasmonate treatment and pathogen attack, can cause chloroplast dysfunction and photosynthetic damage as well as chloroplastic ROS production [10][11][12]. Studies showing the function of ROS in signal transduction networks during plant PCD process have started to emerge [13][14][15].…”

Transcriptional up-regulation of genes involved in photosynthesis of the Zn/Cd hyperaccumulator Sedum alfredii in response to zinc and cadmium

“…The cryo-fractured specimens were dried using freeze-drier, coated with carbon and prepared for observation by SEM. A portable version of an Imaging-PAM Chlorophyll Fluorometer (PAM-MINI, Walz, Effeltrich, Germany) connected to a computer with data acquisition software (ImagingWin v2.0 m, Walz) was used to determine the chlorophyll fluorescence parameters (Li et al, 2012a). Leaves were adapted in darkness for at least 15 min for precise determination of minimal and maximal fluorescence levels in the dark (F o and F m , respectively).…”