Jacalin-related lectins (JRLs) are widely distributed carbohydrate-binding proteins in the plant kingdom, which play key roles in development and pathogen defense.  In this study, we profiled evolutionary trajectory of JRLs family in 30 plant species and identified domain diversification and recombination leading to different responsive patterns of JRLs in rice during defense against rice blast.  All of 30 plant species analyzed in our study have two types of JRLs by containing either a single jacalin or repeated jacalin domains, while chimeric jacalins exist in more than half of the species, especially in the Poaceae family.  Moreover, Poaceae species have evolved two types of unique chimeric JRLs by fusing the jacalin domain(s) with dirigent or NB_ARC domain, some of which positively regulate plant immunity.  Seven Poaceae-specific JRLs are found in the rice genome.  We further found expression of rice JRLs, including four Poaceae-specific JRLs, are induced by Magnaporthe oryzae infections at either early or late infection stages.  Overall, the results present the evolutionary trajectory of JRLs in plant and highlight essential roles of Poaceae specific JRLs against pathogen attacks in rice.