Postdoctoral Associate Cornell University Ithaca, New York
Body of Abstract: Secondary growth is the developmental process by which plants grow thicker. This highly conserved process provides mechanical support for ever-elongating shoots, and a regenerative source of vascular tissues to feed the ever-expanding crown of shoots. Typically, secondary growth generates a core secondary xylem (wood) surrounded by a sheath of secondary phloem (inner bark), and this pattern is achieved through a delicate balance between cell initiation, proliferation, differentiation, and programed cell death – all governed by a single stem-cell region called the vascular cambium. This is a conserved modality shared by thousands of seed plants, and it is also controlled by a shared suite of conserved genes. However, this typical modality has been disrupted in at least 17 different lineages of gymnosperms and angiosperms, where the stem perpetually generates additional vascular cambia––this is called “successive cambia”. In this study, we investigate the evolution and development of successive cambia, with a particular focus in Fabaceae. By comparing Phaseolus vulgaris (regular secondary growth) to Wisteria floribunda (successive cambia), we combine anatomy with comparative transcriptomes to elucidate the developmental and molecular mechanisms underlying successive cambia formation. Moreover, we explore the molecular evolution of conserved genes related to vascular development (WOX4, CLE41, PXY, ER) to test for signatures of selection, gene duplication and pseudogenization in lineages with and without successive cambia.