Poster: Signaling, cell-to-cell

Abs # 447: Tie-dyed1 promotes the sink to source transition in leaves

Presenter:	Braun, David M., dmb44@psu.edu
Authors	Braun, David M. (A)   Ma, Yi  (A)   Inada, Noriko  (B)   Song, Rentao  (C)   Messing, Jo  (C)   Freeling, Michael  (B)
Affiliations:	(A): Pennsylvania State University (B): Univerisity of California-Berkeley (C): Waksman Institute, Rutgers University

We are interested in the signals and genetic programs coordinating leaf cell differentiation and development. We hypothesized that by characterizing mutants with leaf sectors of different identities we might identify genes involved in signal transduction pathways coordinating development among neighboring regions of a leaf. Clonal analyses of maize leaf development reveal that clonal (mother to daughter cell) lineages are arranged longitudinally along the long axis of the leaf. To identify genes coordinating regional leaf identity we screened for mutants with sectors that extend laterally to cells beyond the clonal lineages. A mutant, tie-dyed1 (tdy1), was identified with yellow and green pigmented leaf sectors that violate clonal lineage relationships. We determined that tdy1 sectoring requires high light, is restricted to a narrow developmental time and results in the yellow tissue hyperaccumulating sugars and starch. We hypothesize that Tdy1 integrates developmental, environmental and metabolic signals to promote the switch from a young, carbon importing tissue (sink) to a mature, carbon exporting tissue (source). To characterize tdy1 at the molecular level we isolated additional alleles via a directed Mutator transposon tag. A tightly linked Mu1 element was cloned and used to identify a Bacterial Artificial Chromosome (BAC) containing the flanking sequence. We found that the Mu1 insertion caused an adjacent ~180 kb deletion including the tdy1 locus. A BAC covering this region was sequenced and candidate genes identified. We are currently testing these candidate genes to determine which corresponds to tdy1.