The purification, characterization and ligand-binding kinetics of hemoglobins from root nodules of the non-leguminous Casuarina glauca — Frankia symbiosis

A new hemoglobin gene from soybean: a role for hemoglobin in all plants.

“…More recently, hemoglobin and hemoglobin genes have been discovered in the nonlegume genera Parasponia, Trema, Casuarina, Hordeum, Triticum, and Zea (2)(3)(4)(5)(6)(7)(8). The finding of hemoglobin genes in non-nodulating plants (Trema, Hordeum, Triticum, and Zea) and in phylogenetically diverse plant genera, including monocots, reinforces the proposal that hemoglobin may be present in all plants (9).…”

“…Degenerate primers were designed to conserved regions of plant nonsymbiotic hemoglobins (see Fig. 1) as follows: Hbexonlf (hemoglobin exon 1 forward primer), 5 '-CGGAATTCGA(A/G)GA(A/G)(C/G)A(A/G)GA(A/ G)GCI(T/C)TIGT; Hbexon2f (exon2 forward primer), 5'-CGGAATTCATITT(T/C)GA(A/G)ATIGCICC; Hbexon2r (exon 2 reverse primer), 5'-CGGGATCCGC(A/G)TGIII(T/ C)TTIA(A/G)(T/C)TTIGG(A/G)TT; Hbexon4r2 (exon 4 reverse primer), 5'-CGGGATCCGC(T/C)TC(T/C)TTIAT-IGT(T/C)TC.…”

Hemoglobin in Frankia , a Nitrogen-Fixing Actinomycete

“…These actinorhizal root nodules are modified lateral roots and contain various amounts of hemoglobin ranging from very low concentrations in Purshia to high concentrations in Casuarina and Myrica (18,24). In Casuarina, the hemoglobin (or at least most of it) is produced by the plant (6,12), but the source in other actinorhizal nodules is not known. In nodules from Alnus, which contain intermediate concentrations of hemoglobin, much of the hemoglobin is associated with nodule fractions that contain Frankia (20).…”

Nodules and oxygen

“…In actinorhizal nodules, an O 2 diffusion barrier surrounding the entire infected tissue as found in legume nodules, would cut off the central vascular system from O 2 supply. Nevertheless, one actinorhizal symbiosis exists where oxygen protection mechanisms resemble those found in legumes: in nodules of Casuarina glauca, a class II hemoglobin is present in high concentrations in infected cells (Fleming et al 1987;Jacobsen-Lyon et al 1995), and Frankia does not form vesicles (Berg and McDowell 1988). O 2 -microelectrode analysis has shown that the infected cells of C. glauca nodules are in a low O 2 environment (Tjepkema 1979), presumably due to the fact that their cell walls, and the walls of adjacent uninfected cells, are impregnated with a very hydrophobic lignin (Berg and McDowell 1987).…”