Pyk10, a seedling and root specific gene and promoter from Arabidopsis thaliana.

Pyk10 is a root and hypocotyl specific myrosinase from Arabidopsis thaliana. Northern analysis revealed the root specific expression of pyk10. In order to study the pyk10 promoter and the genomic structure of the gene, a genomic clone was isolated and sequenced. The clone contained the complete pyk10 gene and a promoter region of 3569 bp. The gene spans 2963 bp and consists of 12 exons and 11 introns, a structure that reflects the common gene organization of myrosinases. Within the promoter sequence, different development specific, organ specific, elicitor and plant hormone responsive regulatory elements could be identified, which also occur in other promoters. To determine the pattern of expression, four different 5'-promoter deletion fragments were linked to a ss-glucuronidase (gus) reporter gene and transformed into A. thaliana. The results demonstrated that the pyk10 promoter mediates a developmental gene activity with a strong emphasis in the root. Cis-acting sequences regulating root specific expression were identified to reside in the two promoter fragments B and C.

Isolation of a gene from Arabidopsis thaliana related to nematode feeding structures.

Using a promoter tagging approach, a gene upregulated in nematode feeding structures (NFS) of Heterodera schachtii was identified in Arabidopsis thaliana plants. Sequence analysis of the transgenic line bearing gus reporter gene and the wild-type plant revealed that the T-DNA had been inserted into the promoter of the gene, however, with transcription start points at different sites for the gus reporter gene and for the endogenous gene. This tagged gene, designated pyk20, encodes a transcript of 2.6 kb. Southern blot analysis revealed a single gene copy for pyk20 in the Arabidopsis C-24 genome. Other cruciferous plants were shown to possess pyk20 or homologous genes. The predicted amino acid sequence of the PYK20 protein contains 695 residues with a molecular mass of 78 kDa and includes a glutamine-rich domain in the C-terminal region. IAA and kinetin treatment increased the level of the pyk20 transcript in the plant, whereas ABA treatment and temperature stress reduced the pyk20 transcript level. In-situ hybridisation and Northern blot analysis revealed that the gene is expressed in NFS. Based on homologies of the glutamine-rich domain, the biological role of the pyk20 gene product as a transcription factor is assumed.