Gene Expression and Leaflet Growth: Is There a Molecular Basis for the Absence of a Base-to-Tip Growth Gradient?
Compared to other dicotyledons, soybeans lack a base-to-tip growth gradient in their leaflets. The reason for this anomaly is unknown. This project sought to uncover some of the differences in cellular makeup and gene expression of leaf tissues during the growth phase that may lead to a lack of a growth gradient. Dicotyledons development begins at the tip and ends at the base. This pattern results from cells at the tip ceasing cell division and maturing before those in the base. In the case of the soybean, it is hypothesized that cell division is still occurring in the tip of the leaf. Over the course of the research period, the first trifoliate of 18 soybean plants (Glycine max) were sampled from plants grown in growth chambers with twelve hours of light at 27ºC and twelve hours of darkness at 17ºC. Daily measurements were made on all three leaflets and harvests of the lateral leaflets began on the first day of unfolding and every other day afterwards until the full leaf size was reached. One leaflet was used for RNA extractions and microarrys while the other was used for fluorescence microscopy. Those samples viewed via microscopy showed results in agreement with the hypothesis. In the spongy mesophyll and the palisade mesophyll layers of the tip tissues, cellular division was still occurring. Differences in cell size between the base and tip were small as the cells were similar in size. The microarray analysis the next step to determine genetic expressions of the leaf tissues.
School:
University of Illinois at Urbana-Champaign
Department:
Molecular and Cellular Biology
Research Advisor:
Lisa Ainsworth
Department of Research Advisor:
Department of Plant Biology
Year of Publication:
2006