On the relationship between two indices (“Bulk density” and “dry-matter content”) of dry-matter accumulation in plant organs

“Bulk density” and “dry-matter content” are useful indices of dry-matter accumulation in plant organs. A theoretical equation describing the relationship between these two indices was put forward. To examine the reliability of this equation, the seasonal changes of these two indices were investigated in the leaves and stems of different ages ofAucuba japonica. In each organ both indices varied seasonally almost parallel to each other, but the seasonal changes of dry-matter content were less obvious than those of bulk density. The observed bulk density was always larger than that calculated from the observed dry-matter content by the theoretical equation. A drying experiment showed that this discrepancy was caused by the decrement of the volume of the plant material by water loss during the period from the weight measurement to the volume measurement. When the water loss was negligible, the equation described well the relationships between the two indices of the experimental materials. It was also shown that this equation was useful for the estimation of the amount of air space in plant materials.     

Isolation of Expressed Sequences Encoded by the Human Xq Terminal Portion Using Microclone Probes Generated by Laser Microdissection

The genes that cause a variety of neurologic and neuromuscular disorders have been mapped to the distal region of Xq. In an effort to isolate genes from this area, a regional genomic library of the distal 30% of Xq was constructed from a single metaphase spread by means of laser microdissection and single unique primer-polymerase chain reaction. Using pooled probes of 1000 clones from the genomic library, human brain cDNA libraries were screened for expressed sequences encoded by this region. From the 250,000 cDNA clones screened so far, 10 nonoverlapping sequences that mapped back to the target portion were isolated. The complete nucleotide sequences of these cDNA clones have been determined. Analysis of the sequences indicates that none has significant similarity to previously characterized primate genes. One sequence mapping to Xq27.3-qter contained an open reading frame of 281 amino acids and was expressed in every tissue tested. This gene, as well as others isolated in this manner, may prove to be a candidate gene for heritable disorders mapping to this region.     

Molecular Properties and Extracellular Processing of the Lipase of Staphylococcus warneri M

Staphylococcus warneri M exhibited extracellular lipase activity. By zymogram analysis of extracellular proteins, multiple bands were detected and the profiles changed depending on the bacterial growth phase. N-terminal amino acid sequences of three bands (N1-N3) were determined. From the genome library of S. warneri M whole DNA, the gene-directing lipase activity (named gehC(WM)) was cloned and characterized. The gehC(WM )gene encoded a protein (GehC(WM)), whose calculated molecular mass was 83.4 kDa, and the sequence was similar to the other staphylococcal lipases. Though two lipases have been known from S. warneri 863, GehC(WM) differs from both of them, indicating that this enzyme is the third extracellular lipase of the S. warneri strain. The N-terminal sequences of the N1-N3 polypeptides completely coincided with the deduced amino acid sequences in GehC(WM). GehC(WM) was predicted to be a prepro-protein. In vitro processing and protein sequencing suggested that pro-GehC(WM) is possibly processed by extracellular glutamyl endopeptidase, PROM. Inductively coupled plasma-atomic emission spectrometer analysis showed that purified his-tagged mature GehC(WM) possessed zinc ion. A gehC(WM) knockout mutant was constructed by insertion of an erythromycin resistance gene into the gehC(WM). Zymogram and immunoblot analyses of the gehC(WM )mutant indicated that GehC(WM) was a major extracellular lipase of S. warneri M.     

The membrane peroxin PEX3 induces peroxisome-ubiquitination-linked pexophagy

Peroxisomes are degraded by a selective type of autophagy known as pexophagy. Several different types of pexophagy have been reported in mammalian cells. However, the mechanisms underlying how peroxisomes are recognized by autophagy-related machinery remain elusive. PEX3 is a peroxisomal membrane protein (PMP) that functions in the import of PMPs into the peroxisomal membrane and has been shown to interact with pexophagic receptor proteins during pexophagy in yeast. Thus, PEX3 is important not only for peroxisome biogenesis, but also for peroxisome degradation. However, whether PEX3 is involved in the degradation of peroxisomes in mammalian cells is unclear. Here, we report that high levels of PEX3 expression induce pexophagy. In PEX3-loaded cells, peroxisomes are ubiquitinated, clustered, and degraded in lysosomes. Peroxisome targeting of PEX3 is essential for the initial step of this degradation pathway. The degradation of peroxisomes is inhibited by treatment with autophagy inhibitors or siRNA against NBR1, which encodes an autophagic receptor protein. These results indicate that ubiquitin- and NBR1-mediated pexophagy is induced by increased expression of PEX3 in mammalian cells. In addition, another autophagic receptor protein, SQSTM1/p62, is required only for the clustering of peroxisomes. Expression of a PEX3 mutant with substitution of all lysine and cysteine residues by arginine and alanine, respectively, also induces peroxisome ubiquitination and degradation, hence suggesting that ubiquitination of PEX3 is dispensable for pexophagy and an endogenous, unidentified peroxisomal protein is ubiquitinated on the peroxisomal membrane.     

Growth and reproduction of asexual konjak plants (Amorphophalus konjac K. koch)

To examine the differences of the growth and reproduction of different-aged plants, 0-, 1-, and 2-year plants ofAmorphophalus konjac were investigated. RGR and daily net production per unit productive part, relative net-production rate (α′), of the 0-year plant were largest, although NAR was highest in the 2-year plant. This was due to the large LAR of the 0-year plant, owing to its large SLA. With increase in age, LAR decreased and NAR increased. Thus, it appeared that the age of plant exerts two opposite effects on dry-matter production. Since these effects cancel each other out, differences in RGR and α′ between the two older plants were not significant. We estimated that plant size appears to be primarily responsible for these effects. The 0-year plant showed the least distribution ratio of net production into reproductive (storage) organs, and the highest productivity of the reproductive part. The ratio of the production of corm to total reproductive-part production, the D-reproduction index, was independent of age, and critical size in vegetative propagation could not be detected.