Effector biology during biotrophic invasion of plant cells

Chaudhari, Prateek; Ahmed, Bulbul; Joly, David L; Germain, Hugo

no acids formed a structured domain (unlike the N-terminal part of the protein), and gel filtration revealed that AvrM-A can dimerize. 22 Recently Ve et al. resolved the structure of AvrM and AvrM-A and showed that both possess an L-shaped fold and form a dimer with an unusual nonglobular shape. 25 The avirulence properties of AvrM and AvrL have been described, but yield no clues with regard to their targets and their potential virulence functions. Few rust effectors have been shown to be expressed during infection and translocated to host cells. One of these effectors is rust-transferred protein 1 (RTP1), which belongs to a family of effector proteins specific to the order Pucciniales. 26 RTP1 from Uromyces fabae was the first rust effector demonstrated to localize in host cells, and it was also observed that the transfer of the protein was dependent on the developmental stage of haustoria. 27 RTP1 translocates from the extra-haustorial matrix, where it first accumulates, transits through the cytoplasm, then further moves to the nucleus. 27 Unlike most localization studies cited herein, which are mainly based on green fluorescent protein (GFP) fusion and transient expression, RTP1 localization was assessed by immunolocalization during Uromyces fabae infection using four independently-raised polyclonal antibodies. 27 RTP1 sequence analyses indicated that the C-terminal domain exhibited similarities to cysteine protease inhibitors, and RTP1 was indeed shown to inhibit proteolytic activity. 26