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Indian Journal of Experimental Biology (IJEB) >
IJEB Vol.49 [2011] >
IJEB Vol.49(12) [December 2011] >
| Title: | Differential response of tomato and tobacco to Agrobacterium mediated transformation with cytokinin independent -1 (CKI-1) gene as influenced by cytokinin levels |
| Authors: | Mythili, J B
Saiprasad, G V S
Naveena, C
Rajeev, P R
Upreti, K K |
| Keywords: | Agrobacterium mediated transformation
CKI-1 expression
CKI-1 gene
Cytokinin levels
Selectable marker |
| Issue Date: | Dec-2011 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | Cytokinin independent-1 (CKI-1) gene was identified through its ability to confer cytokinin
independent growth in Arabidopsis
which has led to this gene being advocated as a selectable marker in plant
transformation. Keeping this in view, CKI-1
gene was assessed as a selectable marker by transformation of tobacco (Nicotiana tabacum) and tomato (Lycopersicon esculentum L.).
Overexpression of CKI-1 gene through Agrobacterium mediated transformation in
tobacco and tomato conferred cytokinin independent shoot regeneration (in media
devoid of cytokinin/plant growth regulators) in tobacco, but not in tomato
wherein this ability (cytokinin independence) was conferred to T1 explants of CKI-1 transgenic tomato plant (T0)
regenerated on cytokinin medium. Analysis of cytokinin levels revealed that
cytokinin independent growth upon transformation with CKI-1 gene in tobacco (T0) and tomato (T1) was achieved through
maintaining/regulating higher endogenous cytokinin levels and CKI-1 gene
expression. Levels of CKI-1
transcripts assayed through quantitative RT-PCR suggested that there seemed to
be a threshold level of endogenous cytokinin level, regulated due to external
or internal supply via CKI-1 gene
upto which CKI-1 gene expression
correlated with endogenous cytokinin content and beyond that, either the gene
expression was not induced or it remains same. With the incorporation of CKI-1 gene, it appeared that this
threshold level of endogenous cytokinin might be reduced in crops like tomato
to support shoot regeneration at lower concentration of cytokinin, but could
not be made independent of external supply of cytokinin as in tobacco
suggesting that use of CKI-1 gene as
an effective alternate selection marker could not be universally applicable
across the species. The results of the present study revealed that CKI-1 gene in addition to enhancing
cytokinin levels, was also involved in contributing to the sensitivity to
cytokinin and thus served as a positive regulator of cytokinin signal
transduction. |
| Page(s): | 909-918 |
| CC License: |  CC Attribution-Noncommercial-No Derivative Works 2.5 India |
| ISSN: | 0975-1009 (Online); 0019-5189 (Print) |
| Source: | IJEB Vol.49(12) [December 2011]
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