Microbe-independent entry of oomycete RxLR effectors and fungal RxLR-like effectors into plant and animal cells is specific and reproducible
BM Tyler, SD Kale, Q Wang, K Tao, HR Clark, K Drews, V Antignani, A Rumore …
Molecular Plant-Microbe Interactions

Abstract:

A wide diversity of pathogens and mutualists of plant and animal hosts, including oomycetes and fungi, produce effector proteins that enter the cytoplasm of host cells. A major question has been whether or not entry by these effectors can occur independently of the microbe or requires machinery provided by the microbe. Numerous publications have documented that oomycete RxLR effectors and fungal RxLR-like effectors can enter plant and animal cells independent of the microbe. A recent re-examination of whether the RxLR domain of oomycete RxLR effectors is sufficient for microbe-independent entry into host cells, concluded that the RxLR domains of P. infestans Avr3a and of P. sojae Avr1b alone are NOT sufficient to enable microbe-independent entry of proteins into host and non-host plant and animal cells. Here we present new, more detailed data that unambiguously demonstrate that the RxLR domain of Avr1b does show efficient and specific entry into soybean root cells, and also into wheat leaf cells, at levels well above background non-specific entry. We also summarize host cell entry experiments with a wide diversity of oomycete and fungal effectors with RxLR or RxLR-like motifs that have been independently carried out by the six different labs that co-authored this letter. Finally we discuss possible technical reasons why specific cell entry may have been not detected.