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Two globulin storage proteins have been identified in spores of the ostrich fern, Matteuccia struthiopteris (L.) Todaro. The two proteins comprise a significant amount of the total spore protein, are predominantly salt-soluble, and can be extracted by other solvents to a limited extent. The large 113 Svedberg unit (S) globulin is composed of five polypeptides with molecular weights of 21,000, 22,000, 24,000, 28,000 and 30,000. Each polypeptide has several isoelectric point (pI) variants between pH 5 and 7. The small 2.2S storage protein has a pI > 10.5 and is composed of at least two major polypeptides of 6,000 and 14,000 Mr. Some pertinent information concerning storage proteins in the spores of bacteria and algae is available. Bacteria contain storage proteins that accumulate in large quantities during spore development (26). In Anabaena cylindrica, a cyanobacterium, a storage polypeptide has been identified that is sequestered during spore formation and stationary phase cultures (27,28). In both cases, the function of the storage proteins is similar to that of seeds, providing a readily accessible source of nitrogen upon the resumption of growth.Lower vascular plants also have been shown to contain storage proteins. Reports have described storage protein decline in fern spores during imbibition and germination (22,24). However, since no fern spore storage proteins have been isolated and characterized, the developmental role of these proteins remains unclear.Gymnosperms, a group that contains many higher vascular plants of ancient lineage, contain seed storage proteins within haploid megagametophyte tissue. While investigators have identified storage proteins in various pine species (13, 18), only in the cycad, Macrozamia communis, has gymnosperm storage protein been isolated and partially characterized (1).Clearly more work is required with primitive plant groups in order to determine whether the formation of ancestral storage protein genes occurred before higher vascular plants arose. This paper describes research concerned with the identification, partial characterization, and localization of the principal storage proteins in the spores of the ostrich fern, Matteuccia struthiopteris. The qualitative and quantitative data presented here indicate that fern spores have protein bodies containing globulin storage proteins that are biochemically similar to certain angiosperm seed storage proteins. MATERIALS AND METHODSPlant Material. Mature fertile leaves of Matteuccia struthiopteris (L.) Todaro were collected from several locations in Hanover, NH, in late autumn and spores were released by repeatedly soaking the leaves in water and then drying them at room temperature. Spores were separated from associated organic debris using an Allen Bradley sonic sifter and stored in dark bottles at 4°C. For germination time course studies, 200 mg spores were placed in 100 ml of distilled H20 in a 1-L Erlenmeyer flask and maintained on a 12 h light-dark cycle at 25°C in a growth chamber. Illumination (250 ft-c = 40 AE...

Southern blot analysis has revealed the existence in maize of perhaps 12 members of the nuclear cab multigene family encoding the chlorophyll a- and b-binding proteins of the photosystem II light-harvesting complex. Hybridization with 3' probes derived from unsequenced cDNA clones showed that six members of this family differ from one another with respect to expression in mesophyll and/or bundle sheath cells and regulation by light. An additional member of this family, designated cab-m7, that encodes a 28 kDa primary translation product has now been identified. It has been cloned from a maize genomic library and sequenced to begin to define the bases for differences in the expression of these genes. This cab gene is shown to be strongly preferentially expressed in the mesophyll (vs. bundle sheath) cells of maize. Furthermore, the gene is photo-responsive; although small amounts of cab-m7 mRNA are present in etiolated leaves, the mRNA pool is 8-fold larger after six hours of illumination. DNA sequences upstream of the cab-m7 gene resemble those found in the 5'-flanking regions of some other plant genes.

Onoclea sensibilis was found to contain globulin storage proteins of 2.0S and 11.3S. These globulins, comparable in size and subunit composition to the spore storage proteins characterized in Matteuccia struthiopteris (Templeman, DeMaggio, and Stetler, 1987), declined during imbibition and the initial stages of spore germination. Osmunda cinnamomea, a fern that is only distantly related to Matteuccia, also contained globulin proteins, but these had S values of 5.5 and 11.3. SDS-PAGE analysis revealed extensive differences in banding patterns of the 11.3S protein between Onoclea and Osmunda. This work indicates that while globulin proteins are important storage materials in a variety of ferns they exhibit considerable molecular heterogeneity. The observed heterogeneity in the globulin proteins may be a useful tool to explore evolutionary relationships in the ferns.

The ostrich fern, Matteuccia struthiopteris L., contains two globulin spore storage proteins of 2.2 S and 11.3 S, with physical characteristics similar to those of seed storage proteins of Brassica napus (rapeseed) and Raphanus sativus (radish). By the use of a cloned cDNA that encodes the 1.7 S B. napus storage protein (napin), gene sequences that hybridized with napin were detected in fern nuclear DNA, and a 900-nucleotide homologous mRNA was detected in developing spores. In vitro translation of this fern mRNA produced a 22-kD polypeptide comparable in size to the 21-kD precursor polypeptide identified in Brassica. No hybridizations were observed between the Brassica 12 S clone and either fern DNA or developing spore mRNA.