Project Number: 5335-21000-028-04
Project Type: Reimbursable

Start Date: Sep 01, 2008
End Date: Jun 30, 2011

Objective:
The maize leaf offers a unique opportunity to study how cells respond to their position and differentiate accordingly. The recessive milkweed pod1 (mwp1) mutation was identified by patches of adaxial cell identity on the abaxial surface of the sheath. We cloned the gene and showed that it encodes a member of KANADI (KAN) gene family, previously identified in Arabidopsis for a role in abaxial/adaxial polarity. Class III HD-ZIPIII transcription factors, which are targeted by microRNA mir166, are also known to function in abaxial/adaxial polarity. We propose to determine the mechanisms by which mwp1 regulates leaf cell identity.

Approach:
We will carry out RT-PCR and in situ hybridization to examine the expression of polarity genes in the mwp1 mutant. We will also examine the expression of mwp1 in the available single and double mutants that affect polarity. We will ask whether mwp1 affects the chromatin of polarity genes by comparing methylation in patches that are adaxialized with adjacent tissue. Using mosaic analysis, we will determine in which layer MWP1 acts. These experiments should place mwp1 in a regulatory network that guides cell differentiation. We have identified a second mutation, mwp2, with a similar phenotype and will analyze the expression of polarity markers in this mutant background. We will fine-map the mutation to see if there is an obvious candidate gene. Our results indicate that the KAN family comprises at least 10 genes in the maize genome. We will characterize their transcripts and determine their expression patterns. Ideally we will find KAN genes that function in different tissues. We will also carry out yeast two-hybrid screens to identify interacting proteins. From phylogeny, expression and interaction data, we will select the most interesting genes and obtain mutant alleles using a reverse genetics approach. Documents Reimbursable with NRI. Log 35347.