HAG Effector Evolution in Pyricularia Species and Plant Cell Death Suppression by HAG4

Abstract

Seventy host-adapted gene ( HAG) effector family members from Pyricularia species are found in P. oryzae and three closely related species (isolates LS and 18-2 from an unknown Pyricularia sp., P. grisea, and P. pennisetigena) that share at least eight orthologous HAG family members with P. oryzae. The genome sequence of a more distantly related species, P. penniseti, lacks HAG genes, suggesting a time frame for the origin of the gene family in the genus . In P. oryzae, HAG4 is uniquely found in the genetic lineage that contains populations adapted to Setaria and Oryza hosts. We find a nearly identical HAG4 allele in a P. grisea isolate, suggesting transfer of HAG4 from P. grisea to P. oryzae. HAG4 encodes a suppressor of plant cell death. Yeast two-hybrid screens with several HAG genes independently identify common interacting clones from a rice complementary DNA library, suggesting conservation of protein surface motifs between HAG homologs with as little as 40% protein sequence identity. HAG family orthologs have diverged rapidly and HAG15 orthologs display unusually high rates of sequence divergence compared with adjacent genes suggesting gene-specific accelerated divergence. The sequence diversity of the HAG homologs in Pyricularia species provides a resource for examining mechanisms of gene family evolution and the relationship to structural and functional evolution of HAG effector family activity. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .