Developmental and Structural Section
Stewart, Bonnie L , Tomescu, Alexandru MF .
Phylogenetic patterns of endodermis development across vascular plant lineages.
Radial patterning, a fundamental process comprising specification and spatial arrangement of tissues, is responsible for normal functioning of the plant. Specification of a boundary layer between stele and surrounding ground tissues is a universal aspect of radial patterning: boundary layers can be traced throughout the entire sporophyte body in most plant lineages (endodermis in roots and shoots, starch sheath in stems, bundle sheaths of leaf veins), and are key to plant physiology. In Arabidopsis roots, the endodermis is specified by the interaction of two genes, SHORT-ROOT and SCARECROW. Evidence of the same mechanism controlling boundary layer specification in angiosperm shoots and gymnosperm roots raises the question of whether or not that mechanism may be more broadly conserved across vascular plants. Studies addressing mechanisms of boundary layer specification require thorough understanding of the developmental events leading to the formation of that layer. Here we focus on the development of the endodermis which involves asymmetric periclinal division of an initial layer that also produces another derivative layer. Comparisons between stems and roots across several lineages reveal at least four different patterns in the identity of the initial layer and the fate of the 'other layer'. In leptosporangiate fern roots and Equisetum shoots, the initial layer has procambial identity and the 'other layer' differentiates into cortex. In shoots of Selaginella and leptosporangiate ferns, the initial layer has procambial identity and the 'other layer' differentiates into pericycle. In Equisetum roots, the initial layer has ground meristem identity and the 'other layer' differentiates into pericycle. In the roots of Arabidopsis, the inner layer has ground meristem identity and the 'other layer' differentiates into cortex. Comprehensive documentation of patterns of endodermis development and of their distribution across vascular plant lineages will illuminate the evolution of radial patterning and will inform phylogenetic hypotheses.
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1 - Humboldt State University, Department of Biological Sciences, Arcata, CA, 95521, USA
2 - Humboldt State University, Department of Biological Sciences, Arcata, California, 95521, USA
shoot apical meristem
root apical meristem.
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Wasatch B/Cliff Lodge - Level C
Date: Tuesday, July 28th, 2009
Time: 2:15 PM