A genetic and physical map of the region containing PLASTOCHRON1, a heterochronic gene, in rice ( Oryza sativa L.).

The rice heterochronic gene plastochron1, pla1, shows shorter plastochron and ectopic expression of the vegetative program during the rice reproductive phase resulting in aberrant panicle formation. A genetic and physical map was constructed to isolate the causal gene for the pla1 syndrome. Small-scale mapping was carried out to determine the approximate map position of the pla1 locus, and then a high-resolution genetic map was made for pla1-1, one of the pla1 alleles, using an F(2) population comprising 578 pla1-1 homozygous plants. In a high-resolution genetic map, the pla1-1 locus was found to map between RFLP markers C961 and R1738A on chromosome 10, within a 3.6-cM genetic distance. A physical map encompassing the pla1-1 locus was constructed by overlapping Bacterial Artificial Chromosome (BAC) clones through chromosome walking. PCR-based RFLP markers from BAC-end clones were developed and mapped relative to the pla1 locus. Physical map construction using BAC clones indicated that a BAC clone, B44A10 (167-kb), contained the pla1 locus within 74-kb corresponding to a 0.52-cM genetic distance. Gene prediction of 74-kb region carrying the pla1 locus suggested several candidate genes for the pla1 gene. Identification of a candidate gene for pla1 will be made by sequence analysis of allele variation and cDNA screening.

Shoot organization genes regulate shoot apical meristem organization and the pattern of leaf primordium initiation in rice.

The mechanism regulating the pattern of leaf initiation was analyzed by using shoot organization (sho) mutants derived from three loci (SHO1, SHO2, and SHO3). In the early vegetative phase, sho mutants show an increased rate of leaf production with random phyllotaxy. The resulting leaves are malformed, threadlike, or short and narrow. Their shoot apical meristems are relatively low and wide, that is, flat shaped, although their shape and size are highly variable among plants of the same genotype. Statistical analysis reveals that the shape of the shoot meristem rather than its size is closely correlated with the variations of plastochron and phyllotaxy. Rapid and random leaf production in sho mutants is correlated with the frequent and disorganized cell divisions in the shoot meristem and with a reduction of expression domain of a rice homeobox gene, OSH1. These changes in the organization and behavior of the shoot apical meristems suggest that sho mutants have fewer indeterminate cells and more determinate cells than wild type, with many cells acting as leaf founder cells. Thus, the SHO genes have an important role in maintaining the proper organization of the shoot apical meristem, which is essential for the normal initiation pattern of leaf primordia.

A highly sensitive colorimetric determination of serum copper using alpha, beta, gamma, delta-tetrakis(4-N-trimethylaminophenyl)porphine.

A colorimetric method is presented for the accurate determination of serum copper in 0.1 ml sized samples, using alpha, beta, gamma, delta-tetrakis(4-N-trimethylaminophenyl)porphine. This new reagent has high sensitivity (epsilon 433nm = 5.1 X 10(5) l.mol--1.cm--1), it is water-soluble and has long-term stability at the pH range of 4--9 at room temperature. Metal ions and organic compounds even at levels greater than normally found in serum do not affect the determination. The coefficient of variation of this method is less than 3%. In addition, a good correlation was obtained between this method and the Landers and Zak method (r = 0.98).