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Cytokinin-induced mRNAs in cultured soybean cells
D N Crowell1, A T Kadlecek, M C John
1Department of Biochemistry, University of Wisconsin-Madison 53706.
Abstract:
We have isolated 20 cDNA clones for which the corresponding mRNAs accumulate 2- to 20-fold within 4 hr of cytokinin addition to cytokinin-starved soybean suspension cultures. These changes in mRNA levels precede the greening and cell growth induced by cytokinin in this system. Treatment with cycloheximide before cytokinin addition enhances the accumulation of these messages. In addition, the abundance of these mRNAs is influenced by auxin. We demonstrate that the mRNAs corresponding to the cDNAs in this collection display a variety of patterns of accumulation in the tissues of an intact plant. We also show that different cytokinins induce similar increases in message levels. However, analogs of cytokinin that are much less active in bioassays induce lower levels of message accumulation. Sequence analyses indicate that two of the cDNAs correspond to ribosomal protein genes. The remaining cDNAs are likely to represent previously undiscovered genes that function early in the initiation of plant cell growth and/or chloroplast development.
Insights
Cytokinin rapidly increases specific mRNA levels in soybean cells, preceding growth and greening. These findings reveal new genes involved in early plant cell development and chloroplast formation.
Area of Science:
- Plant Molecular Biology
- Biochemistry
- Cell Biology
Background:
- Cytokinins are key plant hormones regulating growth and development.
- Understanding cytokinin's molecular mechanisms is crucial for agricultural applications.
Purpose of the Study:
- To identify and characterize early cytokinin-responsive genes in soybean.
- To investigate the role of these genes in plant cell growth and chloroplast development.
Main Methods:
- Isolation and analysis of 20 cDNA clones from cytokinin-treated soybean suspension cultures.
- Northern blot analysis to examine mRNA accumulation patterns.
- Sequence analysis of identified cDNA clones.
Main Results:
- Cytokinin addition induced a 2- to 20-fold increase in specific mRNA levels within 4 hours.
- These mRNA changes preceded observable greening and cell growth.
- Auxin influenced the abundance of these mRNAs, and cycloheximide enhanced their accumulation.
- Identified cDNAs represent ribosomal proteins and potentially novel genes involved in early plant cell growth and chloroplast development.
Conclusions:
- Cytokinin rapidly and specifically alters gene expression in soybean suspension cultures.
- The identified genes are likely involved in the early stages of cytokinin-mediated plant cell growth and chloroplast development.