Role of the host cell cycle in the Agrobacterium-mediated genetic transformation of Petunia: evidence of an S-phase control mechanism for T-DNA transfer
Chimeric β-glucuronidase (GUS) gene expression in an efficient Agrobacterium-mediated transformation system utilising mesophyll cells of Petunia hybrida synchronized with cell cycle phase-specific inhibitors (mimosine and colchicine) was used to show the absolute requirement of S-phase for transfer...
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Published in | Planta Vol. 201; no. 2; pp. 160 - 172 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Berlin
Springer-Verlag
1997
Springer |
Subjects | |
Online Access | Get full text |
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Summary: | Chimeric β-glucuronidase (GUS) gene expression in an efficient Agrobacterium-mediated transformation system utilising mesophyll cells of Petunia hybrida synchronized with cell cycle phase-specific inhibitors (mimosine and colchicine) was used to show the absolute requirement of S-phase for transfer and/or integration of the transferred DNA (T-DNA). Flow-cytometric analysis of nuclear DNA content and immunohistological detection of bromodeoxyuridine (BrdUrd) incorporation showed that, prior to phytohormone treatment, most (98%) mesophyll cells were at G0—G1-phase (quiescent phase) and no cell division was occurring. After 48 h and 72 h of phytohormone treatment, there was a rapid increase in S—G2—M-phase populations (> 75%) and a concomitant decrease (down to 24%) in G0—G1-phase cells. Assays of GUS showed that maximum transformation (> 95% of explants) also occurred after this period. Our data showed that mimosine and colchicine blocked the mesophyll cells at late G1-phase and M-phase, respectively. No transformation (= GUS expression) was observed in phytohormone-treated cells inhibited in late G1 by mimosine. However, after removal of mimosine, 82% of the explants were transformed, indicating the non-toxic and reversible effect of the inhibitor. On the other hand, a relatively high transformation frequency (65% of explants) was observed after blocking the cell cycle at M-phase with colchicine. However, only transient, but no stable, gene expression (= kanamycin-resistant callus formation) was observed in colchicine-treated M-phase-arrested cells. Similarly, endoreduplication of nuclear DNA, which occurred during the 48 h of phytohormone treatment in some mesophyll cells and cells located along the minor veins in the leaf explants, resulted in transient GUS expression only. These observations indicate a direct correlation between endoreduplication and transient GUS gene expression. Obviously, for stable GUS gene expression, cell division and proliferation are required, indicating that both DNA duplication (S-phase) and cell division (M-phase) are strongly related to stable transformation. We propose that the present system should facilitate further dissection of the process of T-DNA integration in the host genome and therefore should aid in developing new strategies for transformation of recalcitrant plants. |
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Bibliography: | F60 97G5188 ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 0032-0935 1432-2048 |
DOI: | 10.1007/BF01007700 |