Biomedical subjects

B Scheres

Publications and source records attributed to B Scheres.

22 records · Page 2Linked to original sources

PubMed1993

Cellular organisation of the Arabidopsis thaliana root.

The anatomy of the developing root of Arabidopsis is described using conventional histological techniques, scanning and transmission electron microscopy. The root meristem is derived from cells of the hypophysis and adjacent cells of the embryo proper. The postembryonic organization of the root is apparent in the mature embryo and is maintained in the growing primary root after germination. Cell number and location is relatively invariant in the primary root, with 8 cortical and endodermal cell files but more variable numbers of pericycle and epidermal cells. The organisation of cells in lateral roots is similar to that of the primary root but with more variability in the numbers of cell files in each layer. [3H]thymidine labeling of actively growing roots indicates that a quiescent centre of four central cells (derived from the hypophysis) is located between the root cap columella and the stele. This plate of four cells is surrounded by three groups of cells in, proximal, distal and lateral positions. The labeling patterns of these cells suggest that they are the initials for the files of cells that comprise the root. They give rise to four sets of cell files: the stele, the cortex and endodermis, the epidermis and lateral root-cap and the columella. A model of meristem activity is proposed based on these data. This description of Arabidopsis root structure underpins future work on the developmental genetics of root morphogenesis.

Arabidopsis↗

PubMed1990

The ENOD12 gene product is involved in the infection process during the pea-Rhizobium interaction.

The pea cDNA clone pPsENOD12 represents a gene involved in the infection process during Pisum sativum L.-Rhizobium leguminosarum bv. viciae symbiosis. The ENOD12 protein is composed of pentapeptides containing two hydroxyprolines. The expression of the ENOD12 gene is induced in cells through which the infection thread is migrating, but also in cells that do not yet contain an infection thread. Soluble compounds from Rhizobium are involved in eliciting ENOD12 gene expression. Rhizobium common and host-specific nodulation genes are essential for the production of these compounds. Two ENOD12 genes are expressed in nodules and in stem tissue of uninoculated plants. The gene represented by the cloned ENOD12 mRNA is also expressed in flowers, but a different transcription start may be used.

Amino Acid Sequence↗

PubMed1990

The early nodulin transcript ENOD2 is located in the nodule parenchyma (inner cortex) of pea and soybean root nodules.

A pea cDNA clone homologous to the soybean early nodulin clone pGmENOD2 that most probably encodes a cell wall protein was isolated. The derived amino acid sequence of the pea ENOD2 protein shows that it contains the same repeating pentapeptides, ProProHisGluLys and ProProGluTyrGln, as the soybean ENOD2 protein. By in situ hybridization the expression of the ENOD2 gene was shown to occur only in the inner cortex of the indeterminate pea nodule. The transcription of the pea ENOD2 gene starts when the inner cortical cells develop from the nodule meristem. In the determinate soybean nodule the ENOD2 gene is expressed in the inner cortex as well as in cells surrounding the vascular bundle that connects the nodule with the root central cylinder. The term 'nodule inner cortex' is misleading, as there is no direct homology with the root inner cortex. Therefore, we propose to consider this tissue as nodule parenchyma. A possible role of ENOD2 in a major function of the nodule parenchyma, namely creating an oxygen barrier for the central tissue with the Rhizobium containing cells, is discussed.

Amino Acid Sequence↗

PubMed1990

Sequential induction of nodulin gene expression in the developing pea nodule.

A set of cDNA clones have been characterized that represent early nodulin mRNAs from pea root nodules. By RNA transfer blot analyses, the different early nodulin mRNAs were found to vary in time course of appearance during the development of the indeterminate pea root nodule. In situ hybridization studies demonstrated that the transcripts were located in different zones, representing subsequent steps in development of the central tissue of the root nodule. ENOD12 transcripts were present in every cell of the invasion zone, whereas ENOD5, ENOD3, and ENOD14 transcripts were restricted to the infected cells in successive but partially overlapping zones of the central tissue. We conclude that the corresponding nodulin genes are expressed at subsequent developmental stages. The amino acid sequence derived from the nucleotide sequences of the cDNAs, in combination with the localization data, showed that ENOD5 is an arabinogalactan-like protein involved in the infection process, whereas ENOD3 and ENOD14 have a cysteine cluster suggesting that these are metal-binding proteins. Furthermore, we showed that there is a clear difference in the way Rhizobium induced the infection-related early nodulin genes ENOD5 and ENOD12. A factor acting over a long distance induced the ENOD12 gene, whereas a factor acting over a short distance activated the ENOD5 gene.

Amino Acid Sequence↗