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Three MADS-box genes were identified from a cDNA library derived from young flowers of Eucalyptus grandis W. Hill ex Maiden. The three egm genes are single-copy genes and are expressed almost exclusively in flowers. The egm1 and egm3 genes shared strongest homology with other plant MADS-box genes, which mediate between the floral meristem and the organ-identity genes. The egm3 gene was also expressed strongly in the receptacle or floral tube, which surrounds the carpels in the eucalypt flower and bears the sepals, petals, and numerous stamens. There appeared to be a group of genes in eucalypts with strong homology with the 3 region of the egm1 gene. The egm2 gene was expressed in eucalypt petals and stamens and was most homologous to MADSbox genes, which belong to the globosa group of genes, which regulate organogenesis of the second and third floral whorls. The possible role of these three genes in eucalypt floral development is discussed.

Two cDNA clones encoding endo-␤-1,4-glucanases (EGases) were isolated from a radiata pine (Pinus radiata) cDNA library prepared from immature female strobili. The cDNAs PrCel1 (P ᠪ inus r ᠪadiata cellulase 1 ᠪ ) and PrCel2 encode proteins 509 and 515 amino acids in length, respectively, including putative signal peptides. Both proteins contain domains conserved in plant and bacterial EGases. The proteins PRCEL1 and PRCEL2 showed strong similarity to each other (76% amino acid identity), and higher similarity to TPP18 (73 and 67%, respectively), an EGase cloned from tomato (Lycopersicon esculentum) pistils, than to any other reported EGases. Northern-blot analyses indicated that both genes displayed a similar pattern of expression. The only significant difference was in the level of expression. In situ hybridizations were used to demonstrate that, within differentiating pine reproductive structures, PrCel1 expression was greatest in microsporangia in pollen strobili and near the developing ovule in the seed strobili. Expression was also found in vegetative tissues, especially in regions experiencing cell elongation, such as the elongating region of root tips. Both proteins have an ability to degrade carboxymethylcellulose in vitro. Genomic-blot analysis indicated the presence of a family of EGase genes in the radiata pine genome, and that PrCel1 and PrCel2 are transcribed from distinct one-copy genes.

To evaluate developmental and physiological signals that may influence expression of the dihydropyridine-sensitive "slow"Ca2" channel, we analyzed dihydropyridine receptor (DHPR) mRNA abundance in mouse skeletal muscle. Using synthetic oligonucleotide probes corresponding to the rabbit skeletal muscle DHPR, a 6.5 kb DHPR transcript was identified in postnatal skeletal muscle and differentiated C2 or BC3H1 myocytes, but not cardiac muscle or brain. DHPR gene expression was reversibly suppressed by 0.4 nM transforming growth factor j%-1 or by transfection with a mutant c-H-ras allele, nominal inhibitors of myogenesis that block the appearance of slow channels and DHPR. In contrast, both BC3HI and C2 myocytes containing the activated ras vector expressed the gene encoding the nicotinic acetylcholine receptor subunit, demonstrating that not all muscle-specific genes are extinguished by ras. Denervation stimulated DHPR gene expression less than 0.6-fold, despite 8-fold upregulation of 5-subunit mRNA and reciprocal effects on the skeletal and cardiac aactin genes. Thus, DHPR gene induction is prevented by inhibitors of other muscle-specific genes, whereas, at most, relatively small changes in DHPR mRNA abundance occur during adaptation to denervation. (J. Clin. Invest. 1990. 85:781-789.) calcium channels * differentiation * MyoDI -oncogenes * skeletal muscle transforming growth factor ,8-1