No abstract

Bovine chondromodulin‐I (ChM‐I) purified from fetal cartilage stimulated the matrix synthesis of chondrocytes, and inhibited the growth of vascular endothelial cells in vitro. The human counterpart of this bovine growth regulating factor has not been identified. We report here the cloning of human ChM‐I precursor cDNA and its functional expression in Chinese hamster ovary (CHO) cells. We first identified a genomic DNA fragment which encoded the N‐terminus of the ChM‐I precursor, and then isolated human ChM‐I cDNA from chondrosarcoma tissue by PCR. The deduced amino acid sequence revealed that mature human ChM‐I consists of 120 amino acids. In total, 16 amino acid residues were substituted in the human sequence, compared to the bovine counterpart. Almost of all the substitutions were found in the N‐terminal hydrophilic domain. In the C‐terminal hydrophobic domain (from Phe42 to Val120), the amino acid sequence was identical except for Tyr90, indicating a functional significance of the domain. Northern blotting and in situ hybridization indicated a specific expression of ChM‐I mRNA in cartilage. We also successfully determined the cartilage‐specific localization of ChM‐I protein, using a specific antibody against recombinant human ChM‐I. Multiple transfection of the precursor cDNA into CHO cells enabled us to isolate the mature form of human ChM‐I from the culture supernatant. Purified recombinant human ChM‐I stimulated proteoglycan synthesis in cultured chondrocytes. In contrast, it inhibited the tube morphogenesis of cultured vascular endothelial cells in vitro and angiogenesis in chick chorioallantoic membrane in vivo.

Cartilage is an avascular tissue, and exhibits antiangiogenic properties. Cartilage extracts have been shown to contain an inhibitor for DNA synthesis in vascular endothelial cells in vitro. Here we purified the inhibitory activity in the 10-50 kDa fraction of guanidine extracts from fetal bovine epiphyseal cartilage, and found that the inhibitor was identical with chondromodulin-I (ChM-I). Purified ChM-I inhibited tube morphogenesis of cultured vascular endothelial cells, as well as DNA synthesis. These results indicate that cartilage-specific glycoprotein ChM-I may participate in the maintenance of avascularity and anti-angiogenic properties of cartilage.

When plants interact with certain pathogens, they protect themselves by generating various defense responses. These defense responses are induced by molecules called elicitors. Since long ago, composts fermented by animal feces have been used as a fertilizer in plant cultivation, and recently, have been known to provide suppression of plant disease. Therefore, we hypothesized that the compounds from animal feces may function as elicitors of plant defense responses. As a result of examination of our hypothesis, an elicitor of rice defense responses was isolated from human feces, and its structure was identified as cholic acid (CA), a primary bile acid in animals. Treatment of rice (Oryza sativa) leaves with CA induced the accumulation of antimicrobial compounds (phytoalexins), hypersensitive cell death, pathogenesis-related (PR) protein synthesis, and increased resistance to subsequent infection by virulent pathogens. CA induced these defense responses more rapidly than did fungal cerebroside, a sphingolipid elicitor isolated from the rice pathogenic fungus Magnaporthe grisea. Furthermore, fungal cerebroside induced both types of rice phytoalexins, phytocassanes and momilactones, whereas CA mainly induced phytocassanes, but not momilactones. In the structure-activity relationship analysis, the hydroxyl groups at C-7 and C-12, and the carboxyl group at C-24 of CA contributed to the elicitor activity. These results indicate that CA is specifically recognized by rice and is a different type of elicitor from fungal cerebroside. This report demonstrated that bile acid induced defense responses in plants.

The hormonal change in fruit development of Citrus unshiu was investigated. A remarkable change in the content of auxin and ABA was observed, suggesting that the hormonal balance may affect the physiological abscission of the fruits. The occurrence of IAA, IAM, IAA-Me and ABA in the young fruits was confirmed, while citrus auxin could not be detected.