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Abstract
We report the characterization of a member of the auxin-induced
IAA gene family from zinnia, designated
zIAA8, which is expressed by mesophyll cells differentiating as tracheary elements
in vitro. Transcription of
zIAA8 is upregulated within 3 h after cell isolation in inductive medium, indicating that cells perceive and respond to growth factor stimulus early in culture. Transcript levels of
zIAA8 remain high through 72 h of culture in medium containing auxin and cytokinin or auxin alone, but low in medium containing only cytokinin or control medium lacking growth factors, demonstrating auxin-specific induction and consistent with lack of desensitization to prolonged auxin stimulation.
In situ localization shows
zIAA8 is localized to primary vasculature, root tips, and nascent leaves in zinnia seedlings. The observation that
zIAA8 is expressed during vascular development
in planta supports the hypothesis that expression early in culture reflects early events during normal vascular differentiation. The promoter of
Arabidopsis IAA8 drives expression of the GUS reporter in a pattern in
Arabidopsis similar to that for
zIAA8 in zinnia, suggesting conservation of cis regulatory elements between the species and confirming the results from
in situ localization. The vascular expression pattern of the
IAA8 promoter in leaves mirrors the developmentally regulated auxin gradient in expanding leaf blades. The expression patterns of
zIAA8 and
IAA8 yield new insight into vascular development
in vitro and
in planta, and provide much needed markers for early vascular differentiation.
Citation
Groover, Andrew T.; Pattishall, Amy; Jones, Alan M. 2003. IAA8 expression during vascular cell differentiation. Plant Molecular Biology, Vol. 51: 427-435
