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

Abstract

Plant S1-like nucleases, often referred to as nuclease I enzymes, are the main class of enzymes involved in nucleic acid degradation during plant programmed cell death. The catalytically active site of these enzymes shows a significant similarity 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 Zn(2+)-dependent enzymes, this family also comprises nucleases activated by Ca(2+) and Mn(2+), which implies that the apparently well-known S1 nuclease active site in plant nucleases is able to cooperate with different activatory ions. Moreover, particular members of this class differ in their optimum pH value and substrate specificity. These results shed new light on the widely accepted classification of plant nucleases which is based on the assumption that the catalytic requirements of plant nucleases reflect their phylogenetic origin. Our results imply the need to redefine the understanding of the term 'nuclease I'. Analysis of the phylogenetic relationships between S1-like enzymes shows that plant representatives of this family evolve toward an increase in catalytic diversity. The importance of this process for the biological functions of plant S1-type enzymes is discussed.

The pathogenesis-related protein PR-4b from Theobroma cacao presents RNase activity, Ca2+ and Mg2+ dependent-DNase activity and antifungal action on Moniliophthora perniciosa

“…In conclusion, in cacao, the COC dissolution which occurred in both resistant and susceptible genotypes led to extracellular Ca 2+ availability that may be used by the TcPR-4b for its acting as DNase in resistance mechanisms or in PCD during the infection process. This may be reinforced by the fact that the calcium availability is higher in the apoplasm in normal cells, while an influx of calcium in the intracellular area occurred during PCD [63]. …”

Cellular and molecular aspects of quinoa leaf senescence

“…Nuclease activity is associated with nuclear DNA fragmentation phenomena [34,53]. Plant S1-like nucleases, the main class of single-stranded specific nucleases (often termed as type I nucleases), degrade both RNA and ssDNA during plant PCD [54]. Here, we observed that the activity of neutral nucleases with molecular masses of approximately 38, 33 and 26 kDa was induced at early senescent stages.…”

“…Here, we observed that the activity of neutral nucleases with molecular masses of approximately 38, 33 and 26 kDa was induced at early senescent stages. BFN1 is a nuclease with a molecular mass of approximately 38 kDa which has been detected in Arabidopsis during leaf and stem senescence [54][55][56]. The specific function of BFN1 has not yet been demonstrated, but it has been suggested to be involved in the nucleic acid degradation that takes place during both senescence and developmental PCD [56].…”

Activation of Nucleases, PCD, and Mobilization of Reserves in the Araucaria angustifolia Megagametophyte During Germination

“…Ac343 also presented 55% amino acid identity to the best characterized plant S1-like nucleases, ZEN1 of Zinnia elegans and Arabidopsis ENDO1 (also named bifunctional nuclease1, BFN1). Previous reports have demonstrated that BFN1 and ZEN1 are involved in different forms of PCD (Pérez-Amador et al, 2000; Ko et al, 2012; Lesniewicz et al, 2013). Finally, Ac114 revealed the presence of a conserved DNase-RNase domain, which is characteristic of a family of bifunctional nucleases having both DNase and RNase activity.…”