Phytic acid (PA) is the primary storage compound of phosphorus in seeds accounting for up to 80% of the total seed phosphorus and contributing as much as 1

Understanding peroxidase function in plants is complicated by the lack of substrate specificity, the high number of genes, their diversity in structure and our limited knowledge of peroxidase gene transcription and translation. In the present study we sequenced expressed sequence tags (ESTs) encoding novel heme‐containing class III peroxidases from Arabidopsis thaliana and annotated 73 full‐length genes identified in the genome. In total, transcripts of 58 of these genes have now been observed. The expression of individual peroxidase genes was assessed in organ‐specific EST libraries and compared to the expression of 33 peroxidase genes which we analyzed in whole plants 3, 6, 15, 35 and 59 days after sowing. Expression was assessed in root, rosette leaf, stem, cauline leaf, flower bud and cell culture tissues using the gene‐specific and highly sensitive reverse transcriptase‐polymerase chain reaction (RT‐PCR).We predicted that 71 genes could yield stable proteins folded similarly to horseradish peroxidase (HRP). The putative mature peroxidases derived from these genes showed 28–94% amino acid sequence identity and were all targeted to the endoplasmic reticulum by N‐terminal signal peptides. In 20 peroxidases these signal peptides were followed by various N‐terminal extensions of unknown function which are not present in HRP. Ten peroxidases showed a C‐terminal extension indicating vacuolar targeting. We found that the majority of peroxidase genes were expressed in root. In total, class III peroxidases accounted for an impressive 2.2% of root ESTs. Rather few peroxidases showed organ specificity. Most importantly, genes expressed constitutively in all organs and genes with a preference for root represented structurally diverse peroxidases (< 70% sequence identity). Furthermore, genes appearing in tandem showed distinct expression profiles. The alignment of 73 Arabidopsis peroxidase sequences provides an easy access to the identification of orthologous peroxidases in other plant species and will provide a common platform for combining knowledge of peroxidase structure and function relationships obtained in various species.

The satellite sequence studied was primarily composed of GAA repeats organized in long tracts of heterochromatic DNA. Fluorescent in situ hybridization (FISH) with the GAA satellite (GAA banding) to the chromosomes of barley, wheat, rye, and other Triticeae species produced banding patterns similar to those obtained by N-banding. The GAA-banding patterns of barley are described in detail and those of 12 other Triticeae species are described briefly. In situ hybridization with the GAA-satellite sequence permits identification of all the chromosomes of barley. It is a valuable alternative to other banding techniques, especially in connection with physical gene mapping by FISH. The application of the GAA-satellite sequence for the characterization of genomes in phylogenetic studies of genera containing the sequence is discussed. Key words : Hordeum vulgare, Triticeae, GAA-satellite sequence, chromosome identification, genome differentiation.

Signaling through fibroblast growth factor receptors (FGFRs) is essential for many cellular processes including proliferation and migration as well as differentiation events such as angiogenesis, osteogenesis, and chondrogenesis. Recently, genetic screens in Drosophila and gene expression screens in zebrafish have resulted in the identification of several feedback inhibitors of FGF signaling. One of these, Sef (similarexpression to fgf genes), encodes a transmembrane protein that belongs to the FGF synexpression group. Here we show that like zebrafish Sef (zSef), mouse Sef (mSef) interacts with FGFR1 and that the cytoplasmic domain of mSef mediates this interaction. Overexpression of mSef in NIH3T3 cells results in a decrease in FGF-induced cell proliferation associated with a decrease in Tyr phosphorylation of FGFR1 and FRS2. As a consequence, there is a reduction in the phosphorylation of Raf-1 at Ser³³⁸, MEK1/2 at Ser²¹⁷ and Ser²²¹, and ERK1/2 at Thr²⁰² and Tyr²⁰⁴. Furthermore, mSef inhibits ERK activation mediated by a constitutively activated FGFR1 but not by a constitutively active Ras and decreases FGF but not PDGF-mediated activation of Akt. These results indicate that Sef exerts its inhibitory effects at the level of FGFR and upstream of Ras providing an additional level of negative regulation of FGF signaling.