NIRly there: The chromophore of compounds with intramolecular H bonds have been rigidified by substitution of the protons of the NH⋅⋅⋅N bridges by BR2 groups (R=F, Ph). This stiffening and the polymethine character of the chromophores affords dyes with intense fluorescence at room temperature and high NIR absorption, but virtually no absorption in the visible range (see the picture for an example, —: absorption, ••••: fluorescence).

These authors contributed equally to this paper. SUMMARYIt has been reported that filament-forming surface proteins such as hydrophobins are important virulence determinants in fungi and are secreted during pathogenesis. Such proteins have not yet been identified in obligate biotrophic pathogens such as rust fungi. Rust transferred protein 1 (RTP1p), a rust protein that is transferred into the host cytoplasm, accumulates around the haustorial complex. To investigate RTP1p structure and function, we used immunocytological, biochemical and computational approaches. We found that RTP1p accumulates in protuberances of the extra-haustorial matrix, a compartment that surrounds the haustorium and is separated from the plant cytoplasm by a modified host plasma membrane. Our analyses show that RTP1p is capable of forming filamentous structures in vitro and in vivo. We present evidence that filament formation is due to b-aggregation similar to what has been observed for amyloid-like proteins. Our findings reveal that RTP1p is a member of a new class of structural effectors. We hypothesize that RTP1p is transferred into the host to stabilize the host cell and protect the haustorium from degradation in later stages of the interaction. Thus, we provide evidence for transfer of an amyloid-like protein into the host cell, which has potential for the development of new resistance mechanisms against rust fungi.

Auf dem Weg zu selektiven NIR‐Absorbern: Eine Versteifung der Chromophore durch Substitution des Protons der NH⋅⋅⋅N‐Brücke durch die BR2‐Gruppe (R=F, Ph) führt in NIR‐Farbstoffen mit intramolekularen H‐Brücken infolge des Polymethincharakters der Chromophore zu Verbindungen mit intensiver Raumtemperatur‐Fluoreszenz, starker NIR‐Absorption, aber nur geringer Absorption im sichtbaren Spektralbereich (siehe Beispiel; —: Absorption, ••••: Fluoreszenz).