Cytochrome b5 Reductase Encoded byCBR1Is Essential for a Functional Male Gametophyte inArabidopsis   

Abstract

In all eukaryotes, NADH:cytochrome b5 reductase provides electrons, via cytochrome b5, for a range of biochemical reactions in cellular metabolism, including for fatty acid desaturation in the endoplasmic reticulum. Studies in mammals, yeast, and in vitro plant systems have shown that cytochrome b5 can, at least in some circumstances, also accept electrons from NADPH:cytochrome P450 reductase, potentially allowing for redundancy in reductase function. Here, we report characterization of three T-DNA insertional mutants of the gene encoding cytochrome b5 reductase in Arabidopsis thaliana, CBR1. The progeny of plants heterozygous for the cbr1-2 allele segregated 6% homozygous mutants, while cbr1-3 and cbr1-4 heterozygotes segregated 1:1 heterozygous:wild type, indicating a gametophyte defect. Homozygous cbr1-2 seeds were deformed and required Suc for successful germination and seedling establishment. Vegetative growth of cbr1-2 plants was relatively normal, and they produced abundant flowers, but very few seeds. The pollen produced in cbr1-2 anthers was viable, but when germinated on cbr1-2 or wild-type stigmas, most of the resulting pollen tubes did not extend into the transmitting tract, resulting in a very low frequency of fertilization. These results indicate that cytochrome b5 reductase is not essential during vegetative growth but is required for correct pollen function and seed maturation.

MicroRNAs modulate adaption to multiple abiotic stresses in Chlamydomonas reinhardtii

“…We selected NCR2 as the representative target gene of Cre-miR910 to determine the function of Cre-miR910 since degradome sequencing date revealed that NCR2 is Cre-miR910 target. NCR (or ATR in Arabidopsis ) is a membrane-bound flavoprotein and transfers reducing equivalents from NADPH to diverse P450 monooxygenases that participate in a broad range of reactions in plants, including biosynthesis of secondary metabolites, fatty acids, lipids, defense-related chemicals, and plant hormones505152. In Arabidopsis , the expression of NCR ( ATR2 ) was induced by wounding, high visible light, fungal elicitors, and UV light51.…”

Cytochrome b5 Reductase 1 Triggers Serial Reactions that Lead to Iron Uptake in Plants

“…Cytochrome b5 reductase (CBR) mediates electron transfer from NADH to cytochrome b5. Arabidopsis contains two CBR isoforms, CBR1 and CBR2, which localize to the ER membrane and mitochondrial inner membrane, respectively (Heazlewood et al, 2004;Kumar et al, 2006;Wayne et al, 2013). CBR1 has a key role in fatty acid desaturation in the ER membrane by transferring electrons from NADH to the heme group of cytochrome b5.…”

“…Cytochrome b5 then transfers the electrons to fatty acids desaturase 2 (FAD2) and fatty acids desaturase 3 (FAD3), which introduce double bonds into fatty acids. It has been reported that the cbr1-2 mutant plants have reduced levels of unsaturated fatty acids (particularly 18:3) in seeds (Kumar et al, 2006;Wayne et al, 2013), and that CBR1 has a crucial role in the normal functioning of male gametophytes (Wayne et al, 2013). Thus, CBR1 is a key factor in energy transfer to cellular processes that require energy.…”

Mutation of the Inducible ARABIDOPSIS THALIANA CYTOCHROME P450 REDUCTASE2 Alters Lignin Composition and Improves Saccharification

“…In addition, Arabidopsis has two genes coding for CYTOCHROME B5 REDUCTASE (CBR) proteins. CBR1 is located at the membrane of the endoplasmic reticulum but is mainly involved in electron transport for the biosynthesis of polyunsaturated fatty acids, whereas CBR2 is in the mitochondrial membrane, and there is no evidence yet that it could take part in the endoplasmic reticulum electron transport system (Wayne et al, 2013).…”