Crystal Structure Analysis and the Identification of Distinctive Functional Regions of the Protein Elicitor Mohrip2

Abstract

The protein elicitor MoHrip2, which was extracted from Magnaporthe oryzae as an exocrine protein, triggers the tobacco immune system and enhances blast resistance in rice. However, the detailed mechanisms by which MoHrip2 acts as an elicitor remain unclear. Here, we investigated the structure of MoHrip2 to elucidate its functions based on molecular structure. The three-dimensional structure of MoHrip2 was obtained. Overall, the crystal structure formed a β-barrel structure and showed high similarity to the pathogenesis-related (PR) thaumatin superfamily protein thaumatin-like xylanase inhibitor (TL-XI). To investigate the functional regions responsible for MoHrip2 elicitor activities, the full length and eight truncated proteins were expressed in Escherichia coli and were evaluated for elicitor activity in tobacco. Biological function analysis showed that MoHrip2 triggered the defense system against Botrytis cinerea in tobacco. Moreover, only MoHrip2M14 and other fragments containing the 14 amino acids residues in the middle region of the protein showed the elicitor activity of inducing a hypersensitive response and resistance related pathways, which were similar to that of full-length MoHrip2. These results revealed that the central 14 amino acid residues were essential for anti-pathogenic activity.

Surface frustration re-patterning underlies the structural landscape and evolvability of fungal orphan candidate effectors

“…Eighteen families were detected in over 80% of the species ( Fig 1C, D ), including additional toxin folds such as the β 8 double Greek key of βγ-crystallin and the yeast killer toxin WmKT (Antuch et al, 1996) and the (α-β-α) 2 sandwich of the Ustilago maydis KP6 killer toxin (Li et al, 1999). Among the eighteen broadly conserved families, we identified five previously associated with known fungal effectors ( Fig 1D ): RALPH (Pennington et al, 2019), AA-1 (Gupta et al, 2021; Liu et al, 2014; Chruszcz et al, 2012), HRip2 (Liu et al, 2016), and the 5-helix bundle found in Drechmeria coniospora g7941 effector (6zpp). We identified three additional known effector families ( Fig 1D, Table S4 ): MAX (44 OCEs in 3 species) (de Guillen et al, 2015a), Avr2/ToxA (39 OCEs in 6 species) (Di et al, 2017) and Tox3 (6 OCEs in 5 species) (Outram et al, 2021).…”

The crystal structure of SnTox3 from the necrotrophic fungus Parastagonospora nodorum reveals a unique effector fold and provides insight into Snn3 recognition and pro‐domain protease processing of fungal effectors

“…To date, several structures of effector proteins originating from fungal plant pathogens have been determined, and have provided insights into the biochemical functions of these proteins as well as how they are recognized by the plant (Sarma et al ., 2005; Guncar et al ., 2007; Wang et al ., 2007; Sánchez‐Vallet et al ., 2013; Ve et al ., 2013; Nyarko et al ., 2014; de Guillen et al ., 2015; Maqbool et al ., 2015; Ose et al ., 2015; Liu et al ., 2016; Di et al ., 2017; De la Concepcion et al ., 2018; Hurlburt et al ., 2018; Zhang et al ., 2018). An emerging insight from these structures is the existence of conserved folds, despite having high levels of sequence diversity and originating from fungi that belong to different taxa (reviewed by Franceschetti et al .…”

Enhanced disease resistance and drought tolerance in transgenic rice plants overexpressing protein elicitors from Magnaporthe oryzae

“…Crystallization and preliminary X-ray diffraction analyses of MoHrip1 and MoHrip2 have been reported previously [ 46 , 47 ]. The crystal structures of MoHrip1 was recently determined (Zhang, personal communication), and the crystal structures of MoHrip2 was reported recently [ 48 ]. Although MoHrip1 showed a low similarity with MoHrip2 in terms of its primary structure, both had similar three-dimensional structures composed of β-barrels.…”