The Plant S1-Like Nuclease Family Has Evolved a Highly Diverse Range of Catalytic Capabilities

Plant S1-like nucleases, often referred to as nuclease I en-zymes, are the main class of enzymes involved in nucleic acid degradation during plant programmed cell death. The cata-lytically active site of these enzymes shows a significant simi-larity to the well-described P1 nuclease from Penicillium citrinum. Previously published studies reported that plant S1-like nucleases possess catalytic activities similar to their fungal orthologs, i.e. they hydrolyze single-stranded DNA and RNA, and less efficiently double-stranded DNA, in the presence of zinc ions. Here we describe a comprehensive study of the nucleolytic activities of all Arabidopsis S1-like paralogs. Our results revealed that different members of this family are characterized by a surprisingly large variety of catalytic properties. We found that, in addition to Zn2+-dependent enzymes, this family also comprises nuclease