Download Dissecting the transcriptional regulation underlying

Dissecting the transcriptional regulation underlying kranz anatomy in C4 grasses
Carla Coelho1, Simara Price2, John Gierer1, Henry Priest1, Sarit Weissmann1, Javier GilHumanes3, Joyce van Eck4, Dan Voytas3, Kim Gallagher2, Todd Mockler1, Thomas Brutnell1
1
Donald Danforth Plant Science Center, Saint Louis, MO 63132, USA
Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
3
Department of Genetics, Cell Biology, and Development, and Center for Genome Engineering, University of
Minnesota, Minneapolis, MN 55455, USA.
4
Boyce Thompson Institute for Plant Science, Ithaca, New York 14853, USA.
2
C4 grasses, such as maize and sugarcane, are the most photosynthetically efficient crops in the
world. This productivity is a consequence of both biochemical and anatomical adaptations, and
although the biochemistry is well established, the regulatory networks underlying kranz anatomy
are largely unknown. It has been suggested that a regulatory network involving the
transcriptional regulation of SCARECROW/SHORT-ROOT (SCR/SHR) and the
INDETERMINATE DOMAIN (IDD) transcription factors acts to determine cell identity in the
leaves of C4 species (Slewinski, 2013). To explore the potential function of IDD members in
bundle sheath/mesophyll (BS/M) cell specification, we performed a phylogenetic analysis to
determine orthology of IDD protein sequences derived from maize, Setaria, rice, sorghum and
Arabidopsis. We then analyzed leaf gradient and cell-specific transcriptomic datasets to identify
members that are co-expressed in the leaves of maize, Setaria, sorghum and rice. Four members
of the IDDs are co-expressed in the leaf gradient and are enriched to the mesophyll cells. To
functionally dissect the roles of these IDD gene family members, Y1H and Y2H assays were
performed to define an interaction network of SHR/SCR and IDD members. Loss of function
analyses of these candidates are being evaluated using available Ac/Ds and Mutator populations
and by RNAi and CRISPR/Cas9 in Setaria viridis. We propose a model in which various IDD
family members can act as activators or repressors of BS/M differentiation, depending on
interactions with complex members; and we also present, for the first time, that the
CRISPR/Cas9 system allows efficient gene editing in Setaria viridis.