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12. Viruses in Plants — Fascinating but Treacherous©.

Author

Johansen, I. Elisabeth

Abstract

The article discusses a report on plant viruses, presented at the 15th annual conference of the International Plant Propagators' Society's (IPPS) Scandinavian regional chapter, which was held in Odense, Denmark September 14 to 15, 2006. It describes the impact of plant viruses on human life, characteristics of plant viruses, transmission and control.

Published
2006

13. Recessive Resistance in Pisum sativumand Potyvirus Pathotype Resolved in a Gene-for-Cistron Correspondence between Host and Virus

Author

Johansen, I. Elisabeth, Lund, Ole Søgaard, Hjulsager, Charlotte K., and Laursen, Jesper

Abstract

ABSTRACTPea seed-borne mosaic potyvirus (PSbMV) isolates are divided into pathotypes P-1, P-2, and P-4 according to their infection profile on a panel of Pisum sativumlines. P. sativumPI 269818 is resistant to P-1 and P-2 isolates and is susceptible to P-4 isolates. Resistance to P-1 is inherited as a single recessive gene, denoted sbm-1,and the pathogenicity determinant has previously been mapped to the virus-coded protein VPg. In the cultivar Bonneville, a second recessive gene, sbm-2,confers specific resistance to P-2. By exchanging cistrons between a P-2 and a P-4 isolate, the P3-6k1 cistron was identified as the PSbMV host-specific pathogenicity determinant on Bonneville. Exchange of P3-6k1 did not affect infection on PI 269818, and infection of Bonneville was not altered by substitution of the VPg cistron, indicating that P3-6k1 and VPg are independent determinants of pathotype-specific infectivity. On PI 269818 the pathogenicity determinant of both P-1 and P-2 mapped to the N terminus of VPg. This suggests that VPg from the P-1 and P-2 isolates are functionally similar on this host and that resistance to P-1 and P-2 in PI 269818 may operate by the same mechanism. Identification of VPg–sbm-1and P3-6k1–sbm-2as independent pairs of genetic interactors between PSbMV and P. sativumprovides a simple explanation of the three known pathotypes of PSbMV. Furthermore, analysis of ß-glucuronidase-tagged P-2 virus indicated that sbm-2resistance affected an early step in infection, implying that the P3-6k1 region plays a critical role in potyvirus replication or cell-to-cell movement.

Published
2001
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14. Insertion of Introns: A Strategy to Facilitate Assembly of Infectious Full Length Clones

Author

I. Elisabeth Johansen, Ole Søgaard Lund, Foster, Gary D, Johansen, I Elisabeth, Hong, Yiguo, and Nagy, Peter D

Subjects
Genetics, Infectious clone, Intron, Potyvirus, RNA, Biology, medicine.disease_cause, Virus, Stop codon, SOEing, chemistry.chemical_compound, chemistry, Transcription (biology), Protein biosynthesis, medicine, Escherichia coli, DNA
Abstract

Some DNA fragments are difficult to clone in Escherichia coli by standard methods. It has been speculated that unintended transcription and translation result in expression of proteins that are toxic to the bacteria. This problem is frequently observed during assembly of infectious full-length virus clones. If the clone is constructed for transcription in vivo, interrupting the virus sequence with an intron can solve the toxicity problem. The AU-rich introns generally contain many stop codons, which interrupt translation in E. coli, while the intron sequence is precisely eliminated from the virus sequence in the plant nucleus. The resulting RNA, which enters the cytoplasm, is identical to the virus sequence and can initiate infection Some DNA fragments are difficult to clone in Escherichia coli by standard methods. It has been speculated that unintended transcription and translation result in expression of proteins that are toxic to the bacteria. This problem is frequently observed during assembly of infectious full-length virus clones. If the clone is constructed for transcription in vivo, interrupting the virus sequence with an intron can solve the toxicity problem. The AU-rich introns generally contain many stop codons, which interrupt translation in E. coli, while the intron sequence is precisely eliminated from the virus sequence in the plant nucleus. The resulting RNA, which enters the cytoplasm, is identical to the virus sequence and can initiate infection

Published
2008

15. Penium margaritaceum as a model organism for cell wall analysis of expanding plant cells.

Author

Rydahl MG, Fangel JU, Mikkelsen MD, Johansen IE, Andreas A, Harholt J, Ulvskov P, Jørgensen B, Domozych DS, and Willats WG

Subjects
Cell Culture Techniques, Cell Wall ultrastructure, Chlorophyta anatomy & histology, Chlorophyta growth & development, Chlorophyta metabolism, Microscopy, Electron, Transmission, Plant Cells metabolism, Protoplasts, Cell Wall metabolism, Chlorophyta cytology, Models, Biological, Plant Cells ultrastructure
Abstract

The growth of a plant cell encompasses a complex set of subcellular components interacting in a highly coordinated fashion. Ultimately, these activities create specific cell wall structural domains that regulate the prime force of expansion, internally generated turgor pressure. The precise organization of the polymeric networks of the cell wall around the protoplast also contributes to the direction of growth, the shape of the cell, and the proper positioning of the cell in a tissue. In essence, plant cell expansion represents the foundation of development. Most studies of plant cell expansion have focused primarily upon late divergent multicellular land plants and specialized cell types (e.g., pollen tubes, root hairs). Here, we describe a unicellular green alga, Penium margaritaceum (Penium), which can serve as a valuable model organism for understanding cell expansion and the underlying mechanics of the cell wall in a single plant cell.

Published
2015
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