Genetics and Genomics PhD Candidate University of Florida
Using an in vivo chemical genomics approach, Arabidopsis thaliana plants were transformed with random DNA sequences to produce synthetic peptides and then were screened for phenotypes to identify new molecules that modulate plant growth and development. Seedlings expressing the PEP6-32 peptide exhibited longer hypocotyls and diminished cotyledon expansion when grown under red light. Other red-light-mediated seedling processes such as induction of Lhcb (cab) transcripts or loss of directional growth remained unaffected. Long-term responses, such as repression of flowering time, do not show defects in red light response. A synthesized peptide applied exogenously induced the long-hypocotyl phenotype under red light in non-transformed seedlings. The results indicate that the PEP6-32 peptide causes discrete cell expansion defects during early seedling development in red light, mimicking weak phyB alleles. Structure/function analysis was accomplished by randomizing each codon to produce single amino acid substitutions and testing red light response. Variations enhanced the elongated hypocotyl phenotype by as much as 20% or eliminated it to near wild type levels. Additional analysis will characterize whether the substitutions affect other red-light-mediated traits. Co-immunoprecipitation and affinity chromatography experiments will attempt to identify interacting partners and inform the peptide’s mechanism of action. The findings demonstrate that new chemistries that control discrete facets of plant growth and development may be identified in populations of plants expressing random DNA sequences giving rise to purely synthetic peptides.
Coauthors: Raquel Carvalho – University of Florida;Maureen Clancy – University of Florida;Zhilong Bao – University of Florida;Kevin Folta – University of Florida