A Conserved Amino Acid Sequence in Harpin Family Proteins Required for the Binding of Fibrillin 4 and Activation of the Hypersensitive Response in Plants
W. RAHFELDT (1), C. Li (1) (1) Plant Health Care, Inc, U.S.A.

HrpN is a component of the Type III-Secretion system partially responsible for the pathogenicity of Erwinia amylovora, and is sufficient to elicit the Hypersensitive Responsive (HR) in a range of plant species. Using HrpN as bait, Yeast 2 Hybrid screening revealed Fibrillin 4 to be a binding partner, which is a chloroplast protein associated with photosystem II, thylakoids, and plastoglobules. Through systematic truncation of the HrpN protein sequence and identification of common structural elements, a minimal sequence sufficient for HR elicitation was identified, deemed the HR box. In vitro binding assays reveal that any further mutation of the HR box results in the abolition of Fibrillin 4 binding, in tandem with the loss of in planta HR activity. These binding results hold true for a range Fibrillin 4 homologs, such as Fibrillin 1 in Zea mays and Glycine max. Ongoing studies will elucidate the biological role of Fibrillin 4 in plant pathogen interactions.

Abstract Number: P17-591
Session Type: Poster