1a. Objectives (from AD-416):
To improve soybean composition, further understanding of the function of cotyledon specific genes is needed. Early soybean seedling establishment is dependent on genes and processes that mobilize the nutrients stored in the cotyledons. This project aims to define the set of genes that are expressed in cotyledon post-germination development, and determine the timing of their expression. 1. Characterize patterns of gene expression in soybean cotyledons during various stages of cotyledon development and senesence. 2. Compare expression patterns of genes in late vegetative stage leaves and cotyledons to identify cotyledon-specific patterns of gene expression during senescence.
1b. Approach (from AD-416):
We have used whole transcriptome RNA sequencing to identify genes that change in expression in coyledons during cotyledon development and are specifically expressed in soybean cotyledons. This year we will commence bioinformatic approaches to assign putative functions to these genes, and to compare the patterns of expression in leaves and cotyledons.
3. Progress Report:
Cotyledons (also called the “seed leaves”) are the important storage organ of the soybean seedling. After germination, oils and proteins that were stored within the seed are broken down and mobilized to provide energy for the growing plant. Once these reserves are exhausted, the cotyledons undergo a programmed cell death. (A similar process occurs in leaves at the end of the growing season.) Soybean cotyledons are an excellent model for this process because they are large relative to other plant species. This project aims to identify the genes and the sequence of gene expression involved in the process of protein and oil breakdown and mobilization, and programmed cell death in the cotyledons. This year, cotyledons were collected and gene expression was measured. The two main goals were to establish the stages of development and to identify the genes expressed during these stages. It was found that cotyledon development could be divided into three stages: an early stage where the cotyledons become photosynthetic, an early breakdown stage where the storage proteins and oils are remobilized and a late breakdown stage where all of the structures in the leaf (including cell walls and DNA) are broken down. Data on the individual genes is still under analysis, however results indicate that some groups of genes (for example, genes involved in transporting breakdown products between cells) are regulated together during the final two stages of cotyledon development.