Conserved, Plant Pathogenic Oomycete Motif Functions as a Host-Targeting Signal in P. falciparum–Infected Erythrocytes

<div><p>(A) Sequence alignment of six effectors from P. falciparum HT<i>-</i>secretome (upper panel) and five Avr proteins from the oomycete pathogens <i>Phytophthora</i> and <i>Hyaloperonospora</i> (lower panel). Each sequence contains an 11 amino acid region (black bar) centered on RxL residues (blue). Negatively charged residues (E or D) downstream of the RxL are colored red. Seven residues upstream of the RxL are underlined purple and boxed in the case of PfHRPII.</p><p>(B) Live cells expressing secretory GFP chimeras of AVR3a (residues 21 to 69) with no change (i–iii), or where RRLLRK was replaced by AASTAI (iv–vi), where (ii) and (v) indicate fluorescence images, (i) and (iv) corresponding brightfield images, and (iii) and (vi) the respective merges. Constructs contain SS (black) followed by indicated sequences of AVR3a (orange) and GFP (green). For quantitative analyses, two hundred fluorescent images were analyzed as described in Materials and Methods. Fraction of GFP exported to the erythrocyte cytosol is indicated in (vii). As expected, all parasitized cells express and export the transgene (viii). Standard deviations are shown in pink. In all cases: p, parasite; e, erythrocyte; nucleus is Hoechst-stained (blue); scale bar represents 2 μm.</p>