Rice, one of the world's most important food plants, has important syntenic relationships with the other cereal species and is a model plant for the grasses. Here we present a map-based, finished quality sequence that covers 95% of the 389 Mb genome, including virtually all of the euchromatin and two complete centromeres. A total of 37,544 nontransposable-element-related protein-coding genes were identified, of which 71% had a putative homologue in Arabidopsis. In a reciprocal analysis, 90% of the Arabidopsis proteins had a putative homologue in the predicted rice proteome. Twenty-nine per cent of the 37,544 predicted genes appear in clustered gene families. The number and classes of transposable elements found in the rice genome are consistent with the expansion of syntenic regions in the maize and sorghum genomes. We find evidence for widespread and recurrent gene transfer from the organelles to the nuclear chromosomes. The map-based sequence has proven useful for the identification of genes underlying agronomic traits. The additional single-nucleotide polymorphisms and simple sequence repeats identified in our study should accelerate improvements in rice production.

viruses were injected to follicles on both wings for later studies. Chickens were raised in cages and observed on a daily basis over a two-month period. The regenerated feathers were plucked and examined with a dissection or scanning electron micrograph microscope for abnormalities compared with normal primary remiges. Histology and in situ hybridizationParaffin sections (5 mm) were stained with haematoxylin and eosin or prepared for in situ hybridization following routine procedures 26 . Cryostat sections (10 mm) were stained with X-gal. TUNEL staining was performed using a kit (Roche). Nonradioactive wholemount or section in situ hybridization or section in situ hybridization was performed according to the protocol described 22,26 . After hybridization, sections were incubated with an antidigoxigenin Fab conjugated to alkaline phosphatase (Boehringer Mannheim). Colour was detected by incubating with a Boehringer Mannheim purple substrate (Roche).

Mitogen-activated protein kinase (MAPK) cascades consist of members of three families of protein kinases: the MAPK family, the MAPK kinase family, and the MAPK kinase kinase (MAPKKK) family. Some of these cascades have been shown to play central roles in the transmission of signals that control various cellular processes including cell proliferation. Protein kinase NPK1 is a structural and functional tobacco homologue of MAPKKK, but its physiological function is yet unknown. In the present study, we have investigated sites of expression of the NPK1 gene in a tobacco plant and developmental and physiological controls of this expression. After germination, expression of NPK1 was first detected in tips of a radicle and cotyledons, then in shoot and root apical meristems, surrounding tissues of the apical meristems, primordia of lateral roots, and young developing organs. No expression was, however, observed in mature organs. Incubation of discs from mature leaves of tobacco with both auxin and cytokinin induced NPK1 expression before the division of cells. It was also induced at early stages of the development of primordia of lateral roots and adventitious roots. Thus, NPK1 expression appears to be tightly correlated with cell division or division competence. Even when an inhibitor of DNA synthesis was added during the germination or the induction of lateral roots by auxin, NPK1 expression was detected. These results showed that the NPK1 expression precedes DNA replication. We propose that NPK1 participates in a process involving the division of plant cells.

As they respond to numerous extracellular and intracellular stimuli, plants develop various morphological features and the capacity for a large variety of physiological processes during their growth. If we are to understand the molecular basis of such developments, we must elucidate the way in which signals generated by such stimuli can be transduced into plant cells and transmitted by cellular components to induce the appropriate terminal events. In yeast and animal systems, signal pathways that are known collectively as MAPK (mitogen-activated protein kinase) cascades have been shown to play a central role in the transmission of various signals. The components of these pathways include the MAPK family, the activator kinases of the MAPK family (the MAPKK family) and the activator kinases of the MAPKK family (the MAPKKK family). The members of each respective family are structurally conserved and signals are transmitted by similar phosphotransfer reactions at corresponding steps that are mediated by a specific member of each family in turn. Both cDNAs and genes that encode putative homologues of these components have recently been isolated from plant sources. Some of them have been shown to be related not only structurally but also functionally to members of the MAPK cascades of other organisms. These findings suggest that plants have signal pathways that are analogues to the MAPK cascades in yeast and animal cells but it remains to be proven that plant homologues do in fact constitute kinase cascades.(ABSTRACT TRUNCATED AT 250 WORDS)

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