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Cacti are asexually propagated by offsets and cuttings or sexually via seeds (Johnson and Emino, 1979a). However, many species are slow-growing and do not produce offsets. Seeds are sometimes difficult to obtain (Mauseth, 1977) and seedlings are susceptible to damping-off (Mauseth, 1979). As onefourth of all cacti native to the United States are rare or in danger of extinction (Benson, 1977), in vitro propagation of cacti is an attractive alternative for multiplication and maintenance of valuable germplasm.

Daucus carota L., callus was cultured on various levels of the folate analogs, methotrexate (4-amino-10-methylfolic acid, amethopterin) and aminopter in (4-aminofolic acid). Callus growth was inhibited as analog concentrations were increased from 0.01 μM to 10 μM. Methotrexate concentrations in excess of 10 μM were lethal. In contrast, concentrations of aminopterin in the range of 10 to 100 μM resulted in renewed growth and somatic embryogenesis leading to plant regeneration. This plant regeneration occurred even in the presence of 5.0 mg/l 2,4-D or NAA (concentrations up to fifty times higher than that required to maintain callus growth). These observations reveal that aminopterin at high concentrations, but not methotrexate, triggers somatic embryogenesis in the presence of auxin. All tested levels of aminopterin permitted regeneration in the absence of auxin.

Arcelin is a novel seed protein first found in several accessions of the wild Mexican bean, Phaseolus vulgaris L. var aborigeneus (8). It is closely related to bean lectin, both at the amino acid and nucleotide levels (5). There are five allelic variants of arcelin (4, 6). The Arc 1 (Table I, Fig. 1) protein migrates as two bands on polyacrylamide gels with Mr of 35,000 to 38,000. These two bands are glycosylation variants, because a single band is seen following chemical deglycosylation (7). The presence of arcelin correlates with reduced expression of phaseolin (9), the major seed storage protein in beans. In these seeds, arcelin accounts for about 10% of the total seed protein. Arcelin has been found to have insecticidal properties on bruchid beetles (bean weevils), a prominent bean pest (5). Naturally occurring seeds containing arcelin and artificial seeds containing purified arcelin were resistant to attack by the Mexican bean weevil Zabrotes subfasciatus. Reproduction of the bruchid beetle Callosobruchus maculatus was reduced in the presence of black bean phytohemagglutinin, another plant lectin (2). Two arcelin cDNA sequences have been reported, for Arc 1 (5) and for Arc 2 (3). The sequence reported here is a genomic clone of Arc 1. It is identical with the cDNA for Arc 1 with the exception of a single nucleotide in the 3'-untranslated region.