Anatomic and transcriptomic characterization of the canola (Brassica napus) funiculus during seed development.
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Canola (Brassica napus) is a $19.3 billion industry for the Canadian economy annually, largely because of the demand for the oil derived from the seeds of this crop plant. Seed development and accumulation of important nutrients requires coordinated interactions between all seed regions, including the funiculus. The funiculus is a structure of the seed that serves as the only connection between the filial seed and the parent plant, yet its development and underlying transcriptional programs have not been explored. Using light and transmission electron microscopy, I completed an anatomical study of the funiculus over the course of development, from the mature ovule to the post-mature green seed stage. My results show that all three plant tissue systems of the funiculus undergo profound changes at the histological and ultrastructural level. To understand the programs that orchestrate these changes in the globular stage funiculus, I used laser microdissection coupled with RNA-sequencing. This produced a high-resolution dataset of the mRNAs present in each of the three tissue systems of the funiculus. Various clustering analyses and gene ontology term enrichment analysis identified several important biological processes associated with each tissue system. My data show that cell wall growth occurs in the epidermis, photosynthesis occurs in the cortex, and tissue proliferation and differentiation occurs in the vasculature. The importance of these processes in supporting overall seed growth and development is discussed, which can have profound implications in the genetic modification of the canola seed through manipulating the transcriptional activity of the funiculus.