A study of gene expression during first leaf formation in Spathoglottis plicata
Authors:Stacey Darling-Novak, Lila Luna
Mentor:Stacey Darling-Novak, Professor of Biology, University of La Verne
First leaf formation is critical step in germination and seedling establishment that is mediated by physiological and genetic events. The majority of research conducted on leaf formation has focused on the role of hormones, but expressional studies are necessary to gain a complete understanding of this process. Members of the Orchid family are ideal for such studies because the seeds remain as a mass of undifferentiated cells until leaf initiation occurs. By using this simplified developmental model, the present study aims to identify first leaf genes by conducting cDNA-AFLP analysis on three developmental time points of Spathoglottis plicata. Total RNA was extracted from young seedlings at the protocorm (7 DAC) and leaf initiation (9 DAC) stages of development. The third RNA population was collected from 1 year old seedling leaves. For each sample total mRNA was used to generate cDNA amplified fragment length polymorphisms (AFLPs) with 8 primer sets. Thus far, 35 differentially expressed gene fragments have been identified, 8 of which have been sequenced and analyzed using NCBI BLAST database. The results indicated that a GT-2-like transcription factor was isolated suggesting that phytochrome signaling may play a role in leaf initiation. In addition, an ascorbate peroxidase gene fragment was isolated. While previous studies have shown that leaf expansion is dependent on peroxidase production, the results from this study imply that peroxidases are also necessary early in leaf development.