Biochemical differentiation in the tobacco flower probed with monoclonal antibodies

GENETIC ANALYSIS OF OVULE DEVELOPMENT

Ovules are the direct precursors of seeds and thus play central roles in sexual plant reproduction and human nutrition. Extensive classical studies have elucidated the evolutionary trends and developmental processes responsible for the current wide variety of ovule morphologies. Recently, ovules have been perceived as an attractive system for the study of genetic regulation of plant development. More than a dozen regulatory genes have now been identified through isolation of ovule mutants. Characterization of these mutants shows that some aspects of ovule development follow independent pathways, while other processes are interdependent. Some of these mutants have ovules resembling those of putative ancestors of angiosperms and may help in understanding plant evolution. Clones of several of the regulatory genes have been used to determine expression patterns and putative biochemical functions of the gene products. Newly constructed models of genetic regulation of ovule development provide a framework for interpretation of future discoveries.

The use of antibodies to study the architecture and developmental regulation of plant cell walls

This review covers the generation and use of antibodies to defined components of plant and algal cell walls and how these have contributed to our understanding of the spatial and developmental regulation of cell walls. Particular emphasis is placed upon the generation and characterization of monoclonal antibodies to matrix polysaccharides, extensins, and arabinogalactan-proteins of higher plants, and algal polysaccharides and glycoproteins. Immunolocalization studies are discussed in relation to the identification of molecular domains within cell walls, cell adhesion, cell differentiation, and the establishment of plant interactions with other organisms.

Analysis of a cDNA encoding arginine decarboxylase from oat reveals similarity to the Escherichia coli arginine decarboxylase and evidence of protein processing

Arginine decarboxylase is the first enzyme in one of the two pathways of putrescine synthesis in plants. We purified arginine decarboxylase from oat leaves, obtained N-terminal amino acid sequence, and then used this information to isolate a cDNA encoding oat arginine decarboxylase. Comparison of the derived amino acid sequence with that of the arginine decarboxylase gene from Escherichia coli reveals several regions of sequence similarity which may play a role in enzyme function. The open reading frame (ORF) in the oat cDNA encodes a 66 kDa protein, but the arginine decarboxylase polypeptide that we purified has an apparent molecular weight of 24 kDa and is encoded in the carboxyl-terminal region of the ORF. A portion of the cDNA encoding this region was expressed in E. coli, and a polyclonal antibody was developed against the expressed polypeptide. The antibody detects 34 kDa and 24 kDa polypeptides on Western blots of oat leaf samples. Maturation of arginine decarboxylase in oats appears to include processing of a precursor protein.

Alternative pathways of tobacco placental development: time of commitment and analysis of a mutant

Previous work from our lab identified mutants, Mgr3 and Mgr9, of tobacco (Nicotiana tabacum) that produced unusual elongated green outgrowths from placentae in vivo. Similarly appearing stigmatoid growths were described developing from some in vitro cultures of excised placentae of tobacco (Hicks and McHughen, 1974, 1977). Here we report a developmental analysis and comparison of the unusual stigmatoid outgrowths seen in in vitro cultures of wild-type and mutant placentae, as well as the green outgrowths seen in vivo in the mutants. The growths produced by wild-type and mutant placental cultures in vitro, and the growths produced by the mutants in vivo, are identified as abnormal stigmas and styles. Wild-type in vitro placental cultures also produce outgrowths identified as homologs of whole carpels. Carpel fusion is not required for differentiation of stigma, style, transmitting tract, vascular traces, ovary, and ovules in these structures. The type and extent of stigmatoid growth production depends upon the age of the explant at excision and culture initiation. Before ovule primordium initiation, few growths are seen in culture; for a short window of time afterward, the primordia are competent to give rise to stigmatoid and carpelloid growths when cultured. After commitment to ovule development occurs, the primordia produce only ovules when cultured. The behavior of the mutant placental cultures is dimorphic. Explants from early stages behave similarly to wild-type when cultured, but differences between wild-type and the mutant behaviors in culture arise at the time when the stigmatoid growths begin to appear in vivo in the mutants. These results imply that ovule primordia pass through stages of distinct sequential restrictions of fate, first to growth as gynoecia, and then second to growth as ovules. The mutant strains described here perturb the commitment to differentiation as ovules.