Increased expression of Fe-chelatase leads to increased metabolic flux into heme and confers protection against photodynamically induced oxidative stress

Abstract

Fe-chelatase (FeCh, EC 4.99.1.1) inserts Fe(2+) into protoporphyrin IX (Proto IX) to form heme, which influences the flux through the tetrapyrrole biosynthetic pathway as well as fundamental cellular processes. In transgenic rice (Oryza sativa), the ectopic expression of Bradyrhizobium japonicum FeCh protein in cytosol results in a substantial increase of FeCh activity compared to wild-type (WT) rice and an increasing level of heme. Interestingly, the transgenic rice plants showed resistance to oxidative stress caused not only by the peroxidizing herbicide acifluorfen (AF) as indicated by a reduced formation of leaf necrosis, a lower conductivity, lower malondialdehyde and H2O2 contents as well as sustained Fv/Fm compared to WT plants, but also by norflurazon, paraquat, salt, and polyethylene glycol. Moreover, the transgenic plants responded to AF treatment with markedly increasing FeCh activity. The accompanying increases in heme content and heme oxygenase activity demonstrate that increased heme metabolism attenuates effects of oxidative stress caused by accumulating porphyrins. These findings suggest that increases in heme levels and porphyrin scavenging capacity support a detoxification mechanism serving against porphyrin-induced oxidative stress. This study also implicates heme as possibly being a positive signal in plant stress responses.

Effects of Light-Emitting Diode Irradiation on Growth Characteristics and Regulation of Porphyrin Biosynthesis in Rice Seedlings

“…The principal HO reaction product, biliverdin - IXα, prevents oxidative cell damage as part of the antioxidant machinery in animal cells [28]. Its role in protection against oxidative stress in plant systems is also suggested by other reports [29,30,31]. In addition, HO2 shows strong binding of the heme precursor Proto IX in vitro, implicating a possible function of HO2 in the regulation of tetrapyrrole metabolism [32].…”

“…Leaf tissue (0.1 g) from rice seedlings after 10 days of light exposures or darkness were macerated with liquid N 2 and extracted in 1.5 mL of extraction buffer (methanol:acetone:0.1 N NaOH, 9:10:1, v / v / v ) [31]. The homogenate was centrifuged at 10,000× g for 10 min and the supernatant was taken for HPLC analysis.…”

Influence of exogenous 5-aminolevulinic acid on chlorophyll synthesis and related gene expression in oilseed rape de-etiolated cotyledons under water-deficit stress

“…5B,C). The enhanced expression of FC leads to increased metabolic flux into heme and the heme biosynthesis is transiently up regulated during stress (Kim et al 2014). We assumed that PEG treatment might enhance heme biosynthesis, while the increase in heme has a feedback inhibition in GluTR activity.…”

Perturbed porphyrin biosynthesis contributes to differential herbicidal symptoms in photodynamically stressed rice (Oryza sativa) treated with 5-aminolevulinic acid and oxyfluorfen

“…Porphyrin biosynthesis and degradation are carefully adjusted to the cellular requirements, reflecting the different needs under varying stress conditions [20][21][22][23]. Water stress controls metabolites of the porphyrin biosynthetic pathway through their scavenging to cope with excited-state dynamics of porphyrins in the cell, consequently attenuating the photodynamic stress imposed by drought [24].…”