HD-Zip Class III Transcription factors control root growth and vascular patterning
2012 (English)Conference paper, Poster (Other academic)
Plants take up water and mineral nutrients through their roots, and this is then distributed throughout the plant via the vascular tissues. Hence, root growth and vascular patterning and differentiation are likely intimately connected to optimize water and nutrient uptake. Mutants defective in the developmental control regulators encoded by Class III homeodomain leucine zipper (HD-ZIP III) genes display alterations both in root growth rates and in vascular patterning. In the wild-type root, the water conducting strands are invariantly patterned such that protoxylem, with spiral or annular secondary walls, occupies peripheral positions in the vascular stele, and metaxylem, characterized by reticulate or pitted secondary walls, are found in central positions. This pattern is altered by mutations in the HD-ZIP III genes: the phb-7d gain-of-function mutant has metaxylem also in protoxylem position, while the athb8 cna phb phv quadruple loss-of-function mutant develops protoxylem in both central and peripheral positions. We have recently shown that the miR165/166 targeting the HD-ZIP III genes moves from the surrounding endodermal cell layer to control the levels of the HD-ZIP III factors in the stele, and that xylem cell fate is dependent on HD-ZIP III levels; high levels specify metaxylem and low levels specify protoxylem (Carlsbecker et al. Nature, 465(7296):316-21, 2010). Similarly, the levels of HD-ZIP III factors appear to determine both root growth rate and meristem size. While phb-7d has a short root and small root apical meristem, the athb8 cna phb phv quadruple mutant has a long root and large apical meristem. To determine what genes are under the control of the HD-ZIP III transcription factors in the root meristem, we have conducted analyses of transcriptome changes upon either inducing a gain-of-function allele of PHB or inducing miR165 to reduce HD-ZIP III levels. Our analyses suggest that the HD-ZIP III transcription factors act upstream of secondary cell wall and programmed cell death control genes, consistent with the observed xylem phenotypes, but are also upstream of a genetic pathway controlling meristem size and growth rate. Hence, the HD-ZIP III transcription factors may act to integrate root growth control and vascular patterning.
Place, publisher, year, edition, pages
Biochemistry and Molecular Biology
Research subject Biology with specialization in Physiological Botany
IdentifiersURN: urn:nbn:se:uu:diva-213024OAI: oai:DiVA.org:uu-213024DiVA: diva2:680255
Plant Development and Environmental interactions. 3rd EMBO Conference on Plant Molecular Biology. Matera, May 27-30, 2012