Licentiate thesis, 2012
Changes in global gene expression and auxin dynamics during embryo development in conifersVestman, Daniel
AbstractConifers are of great economical importance, but our knowledge about how the development of conifers is regulated is limited. The over-all aim of this study has been to gain a better understanding of the molecular regulation of embryo development in conifers. This can in turn lead to improved methods in forest tree biotechnology and give insights into the evolution of land-plants. We have used somatic embryos to study early stages during embryo development, with a focus on global changes in gene expression and auxin dynamics. Global changes in gene expression during early embryo development in Norway spruce (Picea abies) were analyzed by using a microarray spotted with 12,536 cDNA clones. This allowed us to pinpoint important molecular events like the establishment of different domains and boundary regions, "nurse cells" having a megagametophyte signaling function and a switch from embryonal to vegetative development. Utilizing the same microarray production used for Norway spruce, we studied comparable stages during Scots pine (Pinus sylvestris) early embryo development, and identified processes such as the initiation of pattern formation. A comparison with the Norway spruce microarray revealed a possible delay in the onset of programmed cell death and polar auxin transport. These are differences that could account for problems with recalcitrance in Scots pine. Two auxin responsive reporter constructs were used to monitor the dynamics of auxin during embryo development in Norway spruce. We could show that auxin is first synthesized and accumulated in the suspensor of early embryos, and that the site of synthesis is shifted to the embryonal mass in late embryos while polar auxin transport relocates the auxin in a basal direction. In maturing embryos, auxin is synthesized in the basal part and distributed throughout the embryo by polar transport. Taken together, this study has revealed important processes during embryo development in Norway spruce and Scots pine and also shown how auxin is dynamically distributed during embryo development in Norway spruce.
KeywordsConifer; Early embryogeny; Late embryogeny; Microarray; Norway spruce; Scots pine; Somatic embryogenesis; Polar auxin transport; GH3
Publisher: Institutionen för växtbiologi och skogsgenetik, Sveriges lantbruksuniversitet
Swedish University of Agricultural Sciences, Department of Plant Biology
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