Mayahuelin, a Type I Ribosome Inactivating Protein: Characterization, Evolution, and Utilization in Phylogenetic Analyses of .

Agaves resist extreme heat and drought. In var. , the central spike of the rosette -containing the shoot apical meristem and folded leaves in early stages of development- is remarkably heat tolerant. We found that the most abundant protein in this organ is a 27 kDa protein. This protein was named mayahuelin to honor Mayáhuel, the agave goddess in the Aztec pantheon. LC-MS/MS analyses identified mayahuelin as a type I RIP (ibosome nactivating rotein). In addition to the spike, mayahuelin was expressed in the peduncle and in seeds, whereas in mature leaves, anthers, filaments, pistils, and tepals was absent. Anti-mayahuelin antibody raised against the var. protein revealed strong signals in spike leaves of , , , and , and moderate signals in , , ssp. , and , indicating conservation at the protein level throughout the genus. As in charybdin, a type I RIP characterized in , mayahuelin from var. contains a natural aa substitution (Y76D) in one out of four aa comprising the active site. The RIP gene family in var. consists of at least 12 genes and is the only member encoding active site substitutions. Unlike canonical plant RIPs, expression of gene in did not compromise growth. The inhibitory activity of the purified protein on a wheat germ translation system was moderate. orthologs from other species displayed one of six alleles at Y76: (Y/Y, D/D, S/S, Y/D, Y/S, D/S) and proved to be useful markers for phylogenetic analysis. Homozygous alleles were more frequent in wild accessions whereas heterozygous alleles were more frequent in cultivars. sequences from different wild populations of and a allowed the identification of accessions closely related to varieties of and var. of . Four accessions and var. were closer relatives of var. than wild accessions or other varieties.