Project Summary
The C4 complex of traits, which includes C4-type carbon fixation shared between
leaf bundle sheath (BS) and mesophyll (M) cells, high venation density, high
plasmodesmatal density at the BS/M interface, and development of a highly
photosynthetic and gas-impermeable BS, has evolved independently at least 50
times from C3-type ancestral species, with particular frequency among the
grasses. The objectives of this project are (1) to compare the patterns of
transcripts, proteins, metabolic activities and anatomical features at discrete
stages and in specific cell types in the C3 grass rice and the C4 grasses maize
and sorghum, and (2) from these datasets, to interpret cellular and subcellular
metabolic differentiation, and to develop a model of the regulatory networks
that govern C4 anatomical and physiological traits, to provide a rationale for
enhancing C3 crops with advantageous C4 traits. To achieve these goals, the
team will first calibrate leaf developmental gradients by documenting the
coincident anatomical and physiological features that define each stage with
precision. Second, defined stages from these calibrated source materials will
be subjected to transcript profiling, comparative proteome analysis, metabolite
analysis, and photosynthetic and vascular activity assays. We will develop
novel methods for transcriptome and proteome analysis using laser
microdissection techniques, and for BS and M cells and vascular strands in
particular. These datasets will be linked through the development of new
informatics tools that will enable rigorous comparative transcriptional and
proteome analysis. We will generate a relational database (C3/C4 DB) that will
enable researchers to query our combined datasets to identify genes and
proteins associated with specific developmental phases, cell types and tissue
types associated with C4 traits. The source materials for these public datasets
will be sufficiently calibrated and cross-referenced to permit the addition of
community data on the same cellular gradient framework. This will provide a
foundation for a systems biology approach to understanding C4 biology.
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